Cambridge International Advanced Subsidiary and Advanced Level

9702 Physics November 2024

Principal Examiner Report f or Teachers

PHYSICS

Paper 9702/11
Multiple Choice

There were too f ew candidates f or a meaningf ul report to be produced.

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 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

PHYSICS

Paper 9702/12
Multiple Choice

Question Question Question Question

Key Key Key Key
Number Number Number Number

1 C 11 D 21 B 31 A

2 A 12 A 22 A 32 B

3 D 13 C 23 C 33 A

4 A 14 D 24 C 34 B

5 B 15 D 25 C 35 B

6 C 16 B 26 B 36 A

7 C 17 C 27 D 37 D

8 B 18 C 28 B 38 B

9 D 19 A 29 B 39 D

10 C 20 C 30 B 40 C

General comments

It is important to caref ully read the text of the question bef ore considering the f our options presented.
Candidates should be familiar with the definitions of physical quantities in the syllabus and would benef it
f rom being able to recognise common misconceptions of definitions, for example conf using def initions f or
units and quantities.

In numerical questions, candidates should be careful to consider SI prefixes and powers of ten and should
be encouraged to apply a common-sense check to their answers to ensure they are a sensible magnitude.

In general, candidates f ound Questions 10, 13, 20, 24 and 34 relatively dif f icult. Candidates f ound
Questions 5, 11, 15, 35, 36 and 38 relatively easy.

Comments on specific questions

Question 2

Around half of candidates correctly selected option A. Option B was also a popular choice. This kinetic
energy (5  107 J) is consistent with a car of mass close to 10 6 kg travelling at 10 m s –1, or a car of mass
1000 kg travelling at 320 m s –1. Candidates should practice making order of magnitude estimates f or
quantities in the syllabus.

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 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

Question 6

Only half of candidates correctly identified that the acceleration of the ball is constant (option C). The options
were all selected roughly equally, suggesting that candidates were guessing. As the majority of candidates
correctly solved Question 5 involving an object f alling with constant acceleration, this suggests that
candidates do not recognise the equivalence of these situations. Candidates should be encouraged to
consider the conditions under which physical models and equations can be applied in addition to calculating
values f rom those models.

Question 8

Many candidates correctly selected option B. A significant number of candidates chose option A suggesting
that the term ‘terminal velocity’ is not well understood.

Question 9

Option A was nearly as popular as the correct option D. Candidates selecting A had found the change in the
magnitude of the speed (4.0 m s–1– 2.8 m s–1) to determine the change of momentum, as opposed to the
change in the velocity (4.0 m s–1 + 2.8 m s–1). This is a common error, and candidates should be reminded to
consider the directions of the object or objects involved in momentum problems.

Question 10

Only a small number of candidates correctly found the lost kinetic energy (option C) by subtracting the total
kinetic energy after f rom the total kinetic energy bef ore the collision. Nearly half of the candidates chose
option B, which is the dif f erence between the kinetic energies of the two carriages bef ore the collision.
Candidates should practice problems involving elastic and inelastic collisions, f inding momenta, velocities
and energies.

Question 13

This was a dif ficult question, and most candidates selected the incorrect option B. These candidates had
used the principle of moments to set up an equation for the moment due to each f orce such as 6.0  7.0 +
6.0  3.0 = 5.0  XP + 5.0  PY and solved for XP + PY. This method is not valid since the forces applied at
X and Y are not perpendicular to the line XY. The correct equation is 6.0  7.0 + 6.0  3.0 = 5.0  XPsin60 +
5.0  PY sin60.

Candidates might find it helpf ul to draw the lines of actions of the f orces on the diagram to identif y the
perpendicular distance to the pivot.

Question 18

Stronger candidates f ound this straightf orward, with the majority selecting option C. Amongst weaker
candidates, options B and D were common choices. These candidates had attempted to determine work
done using a f orce of either 50 N (neglecting g) or 490 N and the distance moved along the ramp, as
opposed to the vertical distance moved. Weaker candidates are not confident with the def inition of work as
f orce  distance moved in the direction of the force.

Question 20

This was challenging f or many candidates. Option D was the least popular, suggesting candidates are
conf ident in recognising that Hooke’s law corresponds to a straight-line region on a stress-strain graph.
Candidates would benefit from practice analysing graphs of stress against strain f or dif f erent materials to
identif y f eatures such as Young modulus, elastic limit and limit of proportionality.

Question 22

Only half of candidates correctly selected option A. Option C was popular, suggesting that most candidates
recognise that the area under a f orce-extension graph represents work done, but many did not realise the
graph presented was force against length. Candidates need to pay close attention to the axis labels and
scales given in graphs.

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 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

Question 24

This was challenging for candidates. Most candidates selected the correct option C or option D, recognising
that the distance PQ represented a whole wavelength. Candidates could improve by practicing analysing
graphical representations of longitudinal waves.

Question 28

Only half of candidates correctly selected option B. Option A was selected nearly as of ten. Candidates
should understand the dif f erence between amplitude and displacement as this is a common
misunderstanding.

Question 32

Fewer than half of the candidates correctly chose option A, suggesting that the concept of the quantisation of
charge is not well understood. A large number of candidates selected option D. Candidates should learn the
def initions of key quantities.

Question 34

This was a dif ficult question, requiring candidates to use I = nAvq and the definition of the number density of
charge carriers, to determine the total number of f ree electrons .

The total number of free electrons, N = n / (cross-sectional area  length), can be substituted into I = nAvq
then rearranged to give N = (IAL) / (Avq) = (IL) / (vq) = 5.3 1022 which is option B.

Options C and D were chosen as frequently as option B, suggesting many candidates, especially weaker
ones, may have eliminated option A, and then guessed. Stronger candidates were more likely to correctly
choose B. Candidates could improve by practicing multi-step problems such as this one in addition to more
straightf orward applications.

Question 39

This was straightforward for stronger candidates, who correctly chose option D. Many candidates selected
options A and B, suggesting that the quark composition of protons and neutrons is not well known, or that
there is some confusion between quarks, nucleons, neutrons and protons. Candidates should know the
meanings of all of these key terms, and how to interpret the nuclear notation 31H.

© 2024
 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

PHYSICS

Paper 9702/13
Multiple Choice

Question Question Question Question

Key Key Key Key
Number Number Number Number

1 D 11 B 21 A 31 A

2 C 12 A 22 D 32 A

3 B 13 D 23 B 33 A

4 C 14 D 24 D 34 B

5 A 15 D 25 C 35 B

6 C 16 A 26 C 36 D

7 A 17 D 27 C 37 C

8 B 18 C 28 A 38 B

9 B 19 C 29 C 39 A

10 C 20 A 30 B 40 D

General comments

It is important to caref ully read the text of the question bef ore considering the f our options presented.
Candidates should be familiar with the definitions of physical quantities in the syllabus and would benef it
f rom being able to recognise common misconceptions of definitions, for example conf using def initions f or
units and quantities.

In numerical questions, candidates should be careful to consider SI prefixes and powers of ten and should
be encouraged to apply a common-sense check to their answers to ensure they are a sensible magnitude.

Candidates struggled on the circuits questions in particular and would benefit from more practical experience
constructing and taking measurements f rom a variety of circuits.

In general, candidates found Questions 2, 33 ,34, 35 and 38 relatively difficult. Candidates found questions
8, 15, 18, 24 and 31 relatively easy.

Comments on specific questions

Question 2

More candidates selected option B than the correct option C. Candidates are required to make reasonable
estimates of quantities within the syllabus, so could have estimated the density of copper and then
calculated the mass, or they could have estimated the mass directly. Candidates could improve by practicing
order of magnitude estimates as part of their studies.

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 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

Question 5

A little over half of the candidates correctly selected option A, recognising that the upthrust is independent of
the density of the cuboids. Amongst weaker candidates, option B was the most popular choice,
demonstrating a common error in thinking the density of the submerged object determines the upthrust.

Question 7

Approximately half of the candidates correctly selected option A. The majority of the other candidates
selected option B, perhaps reasoning that as X experiences no air resistance, it will travel faster. Candidates
should consider that as the initial velocities are the same for X and Y, the acceleration of X will be less (due
to the absence of air resistance) so it will take a longer time bef ore its velocity is reduced to zero.

Question 12

Around half of the candidates selected the correct option A. The f our options were chosen roughly equally,
suggesting that the variation of resultant f orce in this situation is not well understood. Candidates are
expected to understand that the drag force varies with velocity, and so can reason that the highest drag will
occur when the ball is moving fastest, at the point of release. Candidates might benefit from drawing a sketch
of the f orces acting on the tennis ball to help them visualise the resultant f orce.

Question 13

Less than two thirds of candidates correctly selected option D f or this simple def inition. Candidates should
learn the def initions of key quantities in the syllabus.

Question 14

The incorrect option C and the correct option D accounted for the majority of responses to this question. This
suggests that candidates were largely successf ul in setting up an equation based on the principle of
moments for the beam in equilibrium. Those candidates whose moment expressions were based incorrectly
on the mass  distance to the pivot (as opposed to the weight  distance to the pivot) chose option C.
Candidates are reminded to pay attention to the units given in the question.

Question 19

Stronger candidates found this straightforward, with the majority selecting the correct option C. Amongst
weaker candidates, options B and D were common choices. These candidates are not conf ident with the
def inition of work as f orce  distance moved in the direction of the force.

Question 23

Stronger candidates found this straightforward and correctly selected option B. Weaker candidates typically
selected option A, recognising that the area under a f orce-extension curve is equal to the work done, but not
realising that the question asked f or the shaded area only. The dif f erence between the area under the
stretching curve and the area under the contraction curve must represent an energy loss, and the cord starts
and ends with no elastic potential energy, so the correct answer must be option B.

Question 26

The correct option C was chosen by a little under half of candidates. Candidates can determine the period of
the wave (1 / 15 = 0.067 s) and then determine the number of complete cycles in 0.5 s (0.5 / 0.067 = 7.5
cycles). Many candidates then multiplied this by 8.0 mm to get a total distance of 60 mm (option B) not
realising that the particle travels 4  amplitude in a single oscillation. Some candidates instead determined
the wave speed (15  0.12 = 1.8 m s–1) and then determined the distance travelled by a wavef ront in 0.5 s
(1.8  0.5 = 0.90 m) rather than particle P and so selected option D.

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 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

Question 27

Whilst most candidates correctly selected option C, a signif icant minority chose option D. Candidates
commonly conf use period and wavelength in graphical representations of waves, and this should be
practiced frequently. Candidates are reminded to check the axes on the graphs presented, as this can be an
easy way to check the units of a measured distance on a graph, and so determine the quantity.

Question 33

This question proved challenging. All four options were selected frequently suggesting that many candidates
were guessing. Even amongst the strongest candidates only half correctly selected option A. Candidates
could solve this problem by combining their knowledge of the IV characteristics of fixed resistors and diodes.
In series the current will be the same in both components, so no current will be present until the threshold
voltage of the diode is reached.

Candidates could improve by constructing circuits or practicing problems involving combinations of

components beyond resistors, thermistors and LDRs.

Question 34

This question was challenging with half of the candidates selecting the incorrect option D. Stronger
candidates were able to determine the new power using power = work done / time (45.0 / 2.25 = 20 W). They
could then use power is proportional to (p.d.)2 as the resistance is constant to determine the new p.d. using
20 / 5 = new (p.d.)2 / V2.

Many candidates correctly determined the ratio of power af ter and bef ore the change to be 4:1 and so
selected option D, f orgetting that this is the ratio of the potential dif f erences squared.

Question 35

The strongest candidates correctly identified that f or this null method the current I2 had to be zero. Many
candidates selected options C and D, suggesting that null methods are not well understood. Candidates
would benef it f rom practical experience of constructing circuits to demonstrate null methods.

Question 38

This f actual recall question was answered correctly by f ewer than half of candidates. Options A, C and D
were selected roughly equally suggesting that candidates do not have a suff icient knowledge of these key
quantities. A significant minority of candidates believed that the rest mass of a beta-particle is zero (option
A).

Candidates should be able to recall the masses and charges of protons, neutrons and electrons.

© 2024
 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

PHYSICS

Paper 9702/21
AS Level Structured Questions 21

Key messages

• Candidates should pay attention to the instructions given in the question, particularly in explanatory
questions. If the question asks candidates to refer to a particular physical quantity, then not doing so is
unlikely to lead to full credit. Candidates should also be careful not to contradict statements given in the
question stem. For example, if intensity is stated to remain constant, then candidates who state that it
changes and rely on this in an explanation will not be awarded f ull credit.

• Candidates should avoid rounding intermediate answers in a numerical calculation as this can lead to an
incorrect final answer. Candidates should keep intermediate values in their calculators or record them to
several more significant figures than the final answer. Only once the f inal answer has been calculated
should this value be rounded to an appropriate number of signif icant f igures.

• Candidates should explicitly state the subject of any numerical or algebraic equations they use. This is
especially important where more than one equation is used in a question, and when equations are stated
and then rearranged. In some questions, credit can be awarded f or correct statements of physical
equations, but only where the whole equation is clearly known. Candidate should not rely on the
examiner to inf er a subject f or an expression given in the working.

• Candidates should pay attention to the units in which information is presented and take note of any SI
pref ixes.

General comments

The def initions of basic physical quantities within the syllabus were of ten not well known. Even where
candidates’ responses indicated that they recognised the correct quantity, the definition given of ten needed
to be given with more precision to gain credit.

Many candidates could improve by showing more working to support their answers to numerical questions
and presenting it more clearly. Correct working, where present, allows marks to be awarded f or good
methods even where errors then occur.

A signif icant number of candidates omitted large parts of the paper.

There was no evidence that candidates were short of time f or this examination.

Comments on specific questions

Question 1

(a) The def inition of density was generally well known, but some weaker candidates confused density
with weight or mass.

(b) (i) Stronger candidates found the calculation of the density straightf orward. Errors in converting the
dimensions of the block from cm to m were common. Amongst weaker candidates, this proved
challenging with many adding the three given lengths, indicating that calculation of the volume of a
cuboid is not well known. Many candidates correctly def ined density in (a) but were not able to
calculate density in (b)(i), and vice versa.

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 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

(ii) This was a challenging question f or many candidates. Only stronger candidates were able to
calculate the percentage uncertainty in the density by addition of the percentage uncertainties in
the given quantities. Many candidates were unable to calculate the percentage uncertainty in any
of the individual quantities, suggesting that the concept of percentage uncertainty is not well
understood. A significant number of candidates attempted to add the absolute uncertainties in all
f our quantities.

(c) Stronger candidates correctly identified a systematic error that could be present in this experiment .
Weaker candidates often gave responses such as ‘parallax’ or ‘human error’, conf using random
and systematic errors.

Question 2

(a) There were a wide range of answers to this question. Candidates are reminded to learn the
def initions of quantities used in the syllabus. Candidates are also reminded to be precise in their
language when describing mathematical relationships. Phrases such as ‘mass into velocity’ and
‘mass by velocity’ are ambiguous, whereas ‘the product of mass and velocity’ or ‘mass multiplied
by velocity’ are clear.

(b) (i) This question required candidates to read a value of momentum from the diagram and then divide
this by the given mass, which many candidates were able to do successf ully. Several candidates
simply gave the maximum momentum instead. Candidates are reminded to caref ully read the
labels on the axes of the graphs given in the question paper.

(ii) This question was generally well answered, and candidates were of ten able to receive f ull credit
here using their value of velocity f rom (b)(i).

(iii) This ‘show that’ question could be approached in many ways. The most popular methods were to
calculate a velocity at time t = 4.0 s and from there determine acceleration using a = v / t, or to
f ind the resultant f orce acting at t = 4.0 s and calculate acceleration using F = ma. Many
candidates’ working was poorly presented in this question, making it dif f icult to f ollow the
reasoning. It is especially important in ‘show that’ questions that the quantities being calculated are
identified, as it is the physical reasoning, rather than the answer, that is being assessed in these
questions.

(iv) Stronger candidates were able to calculate the correct distance by separately determining the
distances travelled between t = 0 and t = 8.0 s and between t = 8.0 s and t = 12 s. Weaker
candidates attempted to calculate a distance assuming the car was accelerating constantly over
the whole 12 s period. Candidates who assumed that the speed was constant throughout were
unable to be given credit.

(c) This question was difficult for the majority of the candidates, suggesting that candidates f ound it
dif f icult to relate the gradient of the momentum–time graph to acceleration.

Question 3

(a) This def inition was not well known. Many candidates spoke vaguely about an amount of energy or
an amount of force. Stronger candidates were able to describe the product of f orce and distance,
but very few correctly described the product of force and displacement in the direction of the f orce.

(b) This question required candidates to derive the f ormula f or gravitational potential energy . Most
candidates simply stated the formula from memory. A significant number did f ollow the instruction
to state the meaning of symbols, but many described g as simply ‘gravity’ rather than the
acceleration of free fall or the gravitational field strength, which prevented some candidates f rom
receiving credit for identifying the weight as mg. Very few candidates explicitly linked the concept of
work done by the weight to the change in gravitational potential energy.

(c) (i) This was generally well answered, though was of ten omitted by the weaker candidates.

(ii) This was also generally well answered, though was of ten omitted by the weaker candidates.

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 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

(iii) This was well answered by most candidates. Weaker candidates of ten omitted this question.
Although the question asked for efficiency, most candidates gave their answer as a percentage
ef f iciency with a percentage symbol, which was acceptable f or f ull credit.

(iv) This question was answered correctly by many candidates. Some of the weaker candidates f ound
it difficult to connect a power equation to the resistivity equation. However, many candidates who
were not successf ul in earlier parts of (c) were able to gain f ull credit on this question.

Question 4

(a) Of all the definitions questions in the paper, this one was answered correctly most of ten. A f ew
candidates conf used Young modulus with tensile strength.

(b) (i) Most candidates correctly drew a straight line through the origin. Candidates are reminded of the
importance of using a ruler to draw straight lines on diagrams. A f ew candidates ignored that the
wire was stretched within its limit of proportionality and drew a line with a non-proportional region at
the end. This could not be given credit.

(ii) Some candidates correctly identif ied the gradient of a f orce–extension graph as the spring
constant. A significant number confused the graph with a stress–strain graph and so gave their
answer as Young modulus. There were also a number of answers of stress, strain or elastic
potential energy, suggesting that these graphs are not well understood.

(iii) A correct answer here generally correlated with a correct answer to (b)(ii). There were again a
number of answers suggesting stress, strain or Young modulus. Some candidates said ‘work done’
but did not specif y that it was the work done on (or by) the wire and so this was not credited.

(c) This was a dif f icult question. Many candidates were able to identif y the ef f ect of one of the
dif f erences between wires P and Q on the extension, but very f ew candidates were able to
correctly account for the overall effect of all of the differences. Many candidates were also able to
qualitatively state that the extension of Q would be less than that of P, but did not give a
quantitative answer using the given quantitative inf ormation.

Candidates who attempted to discuss this problem using stress and strain generally were able to
perf orm better than those who attempted to make use of E = FL / Ax.

Question 5

(a) (i) This was straightforward for most candidates. A common error was to neglect the minus sign on S.
Several candidates gave incorrect answers where P + R = 40 and Q + S = 19, showing that the
conservation of nucleon number and proton number was generally understood, even though the
nature of – decay was not.

(ii) This was not generally well answered, with only a minority of candidates correctly identif ying Z as
an antineutrino.

(iii) Many candidates were able to identify the particles as leptons. The answers to (a)(ii) showed that
candidates of ten did not know that Z was an antineutrino, but they were at least conf ident in
identif ying the – particle as a lepton.

(b) Many candidates could identif y the nucleon composition of an alpha particle and the quark
composition of both protons and neutrons, and so arrived at the correct answer. Very f ew
candidates made arithmetic mistakes in determining the total number of each type of quark. A
number of candidates misunderstood the question and gave answers in terms of charge.
Candidates are reminded that the quarks are named ‘up’ and ‘down’, and these are better answers
than using shorthand such as ‘’ and ‘’.

Question 6

(a) (i) This was another challenging question. Many candidates recognised that the 90° phase dif f erence
of the waves at the source was significant, but very few were able to state clearly that this led to a
90° phase dif f erence at point O. Most responses tended to be vague, and f ew candidates

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 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

explained that the greatest intensity would occur at a point where the waves were in phase. Many
weaker candidates offered general descriptions of interf erence, or suggested that interf erence
would either not occur at O, or else would be totally destructive.

(ii) Many candidates correctly located point B on the line below O, and a similar number correctly
located it the same distance from O as OA. A common error was to place B at the same point as O,
suggesting that O was assumed to be a point of minimum intensity.

(b) (i) The very weakest candidates tended to omit this question entirely. It was well answered by most
other candidates.

(ii) This was difficult for many candidates. It was common f or candidates of all abilities to omit this
question. Many who attempted to solve it tried to make use of the double slit f ormula, rather than
considering the path dif f erence as a quarter of the wavelength determined in (b)(i).

(iii) This question was also often omitted by the weaker candidates. Those who attempted it usually
f ollowed the instruction to use the double slit formula and were able to obtain the correct answer,
though a significant number incorrectly used the diffraction grating equation with an angle of 90°.

Question 7

(a) (i) Nearly all candidates gave an answer of 0.50 A, but somewhat fewer gave a valid set of working to
justif y that answer. Candidates are reminded that, in ‘show that’ questions, the answer must be
shown, but that it is the working that is being assessed. Many candidates were able to use the
e.m.f . and the terminal p.d. to calculate a value f or ‘lost volts’ that could be then used with the
internal resistance to calculate the correct current.

Some candidates attempted to calculate the external resistance in the circuit, setting up correct
equations in terms of the unknown R, but could not make f urther progress.

(ii) This question was generally straightf orward. Some candidates incorrectly added the internal
resistance to the resistance of 1.0 .

(iii) This question was generally well answered.

(b) (i) Most candidates correctly drew two resistors connected in parallel. A small number of candidates
drew the resistors in series but located on wires running vertically on the page rather than
horizontally. Many candidates’ diagrams could have been improved by careful drawing , with small
gaps between components and wires being common. Candidates are reminded that accuracy in
the drawing of diagrams is as important as accuracy in presenting calculations.

(ii) The majority of the candidates recognised that the terminal p.d. would be less. Many also realised
that the parallel combination of resistors would give a lower resistance than the series combination.
It was much less common for candidates to link these two f acts by considering the ef f ect on the
current in the cell and the effect on the p.d. across the internal resistance. Many candidates stated
that the p.d. was proportional to the resistance, without considering that the current is not constant
when the external resistance is changed.

© 2024
 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

PHYSICS

Paper 9702/22
AS Level Structured Questions 22

Key messages

• Candidates should pay attention to the instructions given in the question, particularly in explanatory
questions. If the question asks candidates to refer to a particular physical quantity, then not doing so is
unlikely to lead to full credit. Candidates should also be careful not to contradict statements given in the
question stem. For example, if intensity is stated to remain constant, then candidates who state that it
changes and rely on this in an explanation will not be awarded f ull credit.

• Candidates should avoid rounding intermediate answers in a numerical calculation as this can lead to an
incorrect final answer. Candidates should keep intermediate values in their calculators or record them to
several more significant figures than the final answer. Only once the f inal answer has been calculated
should this value be rounded to an appropriate number of signif icant f igures.

• Candidates should explicitly state the subject of any numerical or algebraic equations they use. This is
especially important where more than one equation is used in a question, and when equations are stated
and then rearranged. In some questions, credit can be awarded f or correct statements of physical
equations, but only where the whole equation is clearly known. Candidate should not rely on the
examiner to inf er a subject f or an expression given in the working.

• Candidates should pay attention to the units in which information is presented and take note of any SI
pref ixes.

General comments

Most candidates answered questions involving the recall and use of f ormulae well. Def initions were well
known by most candidates, but candidates who were not awarded f ull credit of ten either missed out key
words or used wording which changed the meaning of the def inition.

Many candidates could improve by showing more working to support their answers to numerical questions
and presenting it more clearly. Correct working, where present, allows marks to be awarded f or good
methods even where errors then occur.

A significant number of weaker candidates omitted large parts of Question 5, suggesting that the analysis of
circuits was not well understood.

There were several questions on the paper that required candidates to draw on diagrams provided. A
significant number did not use a ruler to help them draw straight lines, making it dif f icult to judge if the line
was intended to be straight. Candidates should be aware that accuracy in drawing diagrams is as important
as accuracy in calculations or in written answers.

There was no evidence that candidates were short of time f or this examination.

© 2024
 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

Comments on specific questions

Question 1

(a) The def inition given f or a vector quantity was usually good.

(b) (i) Most candidates knew the SI base units for force, radius and velocity. Occasionally, candidates
gave the unit of force as N, confusing an SI unit with an SI base unit. Some candidates gave the
units of v as m3, confusing velocity with volume. Weaker candidates sometimes gave the units of D
as kg m–3, incorrectly assuming that D represented density. Arithmetic errors were common
especially when dealing with seconds, leading to kg m –1 s –3.

(ii) Stronger candidates were able to correctly account f or the directions of the three f orces and so
gave a valid equation. Weaker candidates often got the sign of one of the f orces incorrect. Some
stronger candidates tried to include a resultant force term, but rarely made clear that the resultant
f orce was equal to zero as the sphere was moving with terminal velocity, and so could not be
awarded credit.

(iii) Many candidates correctly applied the upthrust formula and f ormula f or the volume of a sphere.
Power-of-ten errors in converting the radius to m were common, but could be awarded credit on the
principle of error carried forward. A large number of candidates did not connect the weight of the
sphere to the equation in (ii) and so simply stated the weight of the sphere as equal to the weight
of the displaced liquid. Some candidates incorrectly equated the upthrust to the drag f orce, and
tried to determine a new volume or density f or the sphere.

Question 2

(a) Most candidates recalled the definition of momentum, and most candidates correctly described a
product of mass and velocity rather than giving the vague answer ‘mass into velocity’. Weaker
candidates sometimes conf used moment and momentum, or described ways to calculate an
impulse such as ‘f orce times time’.

(b) This was generally well answered, with candidates using either F = p / t or f inding acceleration
and then using F = ma. Those candidates who f irst f ound acceleration were more prone to
rounding their acceleration before finding the force, leading to a common incorrect answer of 8.6 N.
Candidates are reminded that they should keep intermediate values in their calculator, or write
them down to several more signif icant f igures than their intended f inal answer, to avoid early
rounding errors.

(c) This straightforward question was answered well by most candidates. Common errors included
assuming that the initial velocity at A was 0, or neglecting to square the second time term in
s = ut + ½at2. Very weak candidates sometimes calculated the distance by using the wrong
equation of ‘initial speed × time’.

(d) (i) This was straightf orward f or most candidates.

(ii) There were a wide variety of lines drawn on the graph. Only the strongest candidates were
awarded f ull credit, with a majority of candidates assuming that the kinetic energy began at 0, and
neglecting the speed given at A in the question. Candidates are reminded to caref ully read the
axes on printed graphs and to consider this inf ormation in the context of the question.

Many candidates drew curved lines between distance = 0 and distance = x, perhaps conf using a
speed against distance graph with an energy against distance graph. Many candidates also drew a
line with a negative gradient from distance = x to distance = x + 18 m, neglecting that the question
states that the velocity is constant over this distance. For those candidates who attempted to draw
a horizontal line over this range, the lines were f requently freehand and very wobbly. Candidates
are reminded to make use of a ruler when drawing straight lines on graphs.

Question 3

(a) (i) Nearly all candidates correctly stated E = stress / strain and so could be awarded at least partial
credit.

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A small number of candidates jumped straight to a substitution without stating the equation they
were using. It was not always clear that these candidates were using a stress divided by a strain,
and so partial credit could not always be awarded. Candidates are reminded to state the equations
they are using bef ore making a substitution.

Power-of-ten errors were very common in this question, especially in reading the percentage strain
f rom the graph. Many candidates used 1.0 for the strain instead of 0.01 and arrived at an answer of
2.4 × 108 Pa. Another common error was to use the stress and strain at E, rather than a pair of
values f rom the linear region.

(ii) Many candidates correctly placed Q at 1.0% strain. Some candidates found it difficult to locate the
end of the linear region of the graph and placed Q at slightly higher values of strain. Stronger
candidates often made use of a ruler and extrapolated the straight line region, making the location
of Q easy to identif y at the point where their straight line and the printed line diverged.

Weaker candidates sometimes confused the limit of proportionality with the ultimate tensile stress,
or possibly with a f ailure point and so located Q beyond E on the diagram.

(b) Most candidates correctly recalled one of the conditions f or equilibrium, with the stronger
candidates recalling both. The most common error was for candidates to describe force or moment
being zero, without ref erring to the resultant f orce or moment.

Occasionally candidates confused moment and momentum. Many weaker candidates also referred
to a constant acceleration or velocity, or stated that an object must be stationary. As these
conditions may be true but are not necessary, these ref erences were ignored.

(c) (i) This question proved challenging, with only the strongest candidates receiving f ull credit. Many
candidates were able to give an expression f or a single correct moment. It was common f or
candidates to correctly determine the distance of one of the forces from point A, but then incorrectly
determine the distance for one of the other forces, resulting in very few correct moment equations.
Other common errors included neglecting the moment of one of the forces entirely or f orgetting to
include the distance of T f rom the pivot.

(ii) This was generally well answered with error carried f orward f rom (i). Most candidates explicitly
stated stress = f orce / area and so could receive some credit even in the case of subsequent
errors. Some weaker candidates gave the area as their final answer for the radius, or attempted to
use an incorrect area f ormula such as the area of a sphere or a cylinder, but this was rare.

(iii) Candidates found this question difficult. Some candidates were able to identif y that the stress (or
more rarely strain) remained relatively small, but the majority of candidates compared this stress to
the limit of proportionality rather than the elastic limit. The difference between the elastic limit and
the limit of proportionality was clearly not well understood.

Many weaker candidates incorrectly stated that the elastic limit or limit of proportionality had
already been exceeded in the initial situation in (c), demonstrating that they did not understand
what is being shown in Fig. 3.1. Another common misconception amongst weaker candidates was
that doubling the stress would cause the Young modulus to double.

Question 4

(a) There were many very good, concise responses to this question. Candidates who read the
question carefully and made use of the terminology presented typically found this straightf orward.

Many responses were vague, especially in their description of directions. Candidates f requently
ref erenced ‘the wave’ or ‘the direction of the wave’ or ‘the direction of motion’ or ‘the direction of
propagation of the wave’. These ambiguous responses were not credited as the question
specif ically asked f or candidates to ref er to ‘the direction of transf er of energy’.

Candidates often compared the direction of transfer of energy with the direction of propagation,
perhaps conf using propagation and oscillation.

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Some weaker candidates did not mention oscillations at all, and gave meaningless responses such
as ‘the wave travels parallel to the energy’ or ‘the wave moves perpendicular to the wave’.

(b) (i) Most candidates correctly located an antinode at the open end of the pipe.

(ii) Nearly all candidates stated v = f . Stronger candidates correctly determined the wavelength and
f ound this straightforward. The most common error was to use the length of the pipe of 4.5 cm as
the wavelength. Some candidates used double the length as the wavelength, perhaps treating the
pipe as having two open ends.

Some candidates jumped straight into a substitution using 4.5 cm, without f irst stating the wave
equation. Typically this meant that they could not be awarded credit, as using the length of 4.5 cm
did not imply a wavelength.

A significant minority attempted to use the Doppler effect equation, confusing the new position of
the piston with a constantly moving source.

(iii) This question was generally well answered by stronger candidates. It was challenging to explain
the causality of the changes to frequency and wavelength correctly, but the connection between a
lower f requency and a longer wavelength or a longer node–antinode distance was usually made
correctly. Weaker candidates frequently appeared to guess at the answer and made little ef f ort to
justif y their choice.

Question 5

(a) This was the least well answered of the three def inition questions on this paper. Candidates
f requently gave ambiguous or incorrect responses that did not make clear that potential dif f erence
is a ratio between energy transf erred and charge. Common incorrect answers included ‘energy
transf erred by a charge’ or ‘energy transferred when unit charge passes’. Both of these def initions
describe an energy rather than a ratio between energy and charge and so are not correct.

It was also common f or candidates to include units, which are not required in the def inition of
physical quantities and may prevent a candidate f rom giving a correct answer. ‘Work done per
coulomb’, f or example, cannot be awarded credit as it is a mixture of quantities and units.

A f ew candidates conf used the def inition of electromotive f orce and potential dif f erence.

Very weak candidates of ten stated ‘current × resistance’ which is an equation f or calculating
electric potential dif f erence and does not def ine it.

(b) (i) This was a straightforward question for those candidates who had learned the circuit symbols. The
most common incorrect answers were ‘variable resistor’ and ‘thermistor’.

(ii) This was a straightf orward question f or nearly all candidates.

(iii) Stronger candidates found this easy. Many candidates attempted to calculate I 2, but ignored the
6.0 V potential difference across the 0.86  resistor despite having just shown this quantity in (ii).

Weaker candidates often used the 6.0 V and divided by the 2.4  resistance to get a current of
2.5 A. This approach uses wrong physics and could not be awarded credit, and f requently this
same misconception meant that few marks could be awarded in (iv). Candidates are encouraged
to annotate the electrical circuit with the known or calculated quantities to help them keep track of
the dif f erent potential dif f erences and currents throughout the circuit.

Some candidates attempted to determine the parallel combination of resistances. This was difficult
due to the unknown resistance of X and only the very strongest candidates made progress with this
method.

(iv) Stronger candidates were able to use their current from (iii) to determine the pd across X. Many
candidates again did not account for the 6.0 V potential difference across the 0.86  resistor and
so could not correctly determine the potential dif f erence across X. Very weak candidates of ten
calculated the potential difference across the 2.4  resistor instead of across component X. Some

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candidates attempted to use the parallel combination of resistances, or carried through a value of
the resistance of X f rom (iii). Again, only the strongest candidates were successf ul.

(v) Most candidates could be awarded credit for a correct power equation, and many were able to use
their values of current and potential difference f rom (iii) and (iv) to gain credit f or power with an
error (or two) carried f orward. Candidates who used a resistance calculated while answering
previous questions often did not show how that resistance was calculated in this question. As the
resistance of X was not required in either (iii) or (iv), it was of ten unclear how candidates had
f ound the value.

(vi) Very f ew candidates gave a f ully correct equation f or the ef f iciency of the circuit. Many stated a
truncated formula such as ‘out / in’ without being explicit that they meant the useful power out and
total power in. Candidates are reminded to be careful and precise in presenting their work. Some
candidates incorrectly inverted the equation, or gave statements that would evaluate to 100% if
taken at f ace value.

Many candidates received partial credit by implication from a correct substitution, and many who
had f ound earlier parts of the question difficult were still awarded f ull credit here with error carried
f orward.

A common error was to assume that current was the same in X as in the power source and so the
ef f iciency was (p.d. in X) / 230 V.

Nearly all candidates gave the f inal answer as a percentage.

(vii) No reasoning was required for this question, so most candidates gave a one-word answer, which
was either correct or incorrect. Those candidates that did give reasons of ten demonstrated
misconceptions that the current must always remain the same based on incorrect application of
Kirchhoff’s first law, or that the total resistance would decrease due to the removal of the 170 
resistor, and so the current must increase.

Question 6

(a) This was challenging for many candidates. Many candidates gave the nuclear notation f or alpha-
and beta-plus particles, but did not explain what this represented. Some candidates did go on to
explain the number of nucleons and protons in an alpha particle, but did not relate this explicitly to
mass or charge. It was very common for weaker candidates to incorrectly state that a beta-plus
particle was a proton.

Candidates often correctly stated that the mass of the alpha particle was greater than that of the
beta-plus particle, but very f ew stated that it was much greater or attempted to quantif y the
dif ference. A large number of stronger candidates went on to correctly give the masses of both the
alpha and beta particles, usually in terms of u. A large number of candidates correctly gave the
mass of the alpha particle, but then incorrectly stated that the mass of the beta particle was zero,
suggesting a conf usion between the nucleon number of a beta particle and its actual mass.

Many candidates correctly identified the magnitudes of the charges of both particles, usually by
explicitly stating them in terms of e. Candidates who gave the charges explicitly as +1e and +2e
were also credited with identifying both charges as being positive. Some weaker candidates did not
make clear that both charges were positive.

(b) (i) This question was generally well answered. A common incorrect answer was to locate Q at
(86, 220), implying an alpha particle had been absorbed by P. It was also common f or very weak
candidates to locate Q half-way between P and R at (83.5, 214), suggesting that these candidates
did not have a good grasp of nuclear concepts.

(ii) This was straightforward for many candidates. Weaker candidates conf used beta-plus and beta-
minus decay. Many also included an alpha particle, suggesting that they had not carefully read the
question.

Candidates should be reminded to be careful with their terminology, as many gave the ambiguous
particle ‘anti-electron neutrino’. An electron antineutrino is correct, but an anti-electron is a positron.

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(c) (i) This question proved to be difficult for most candidates. The strongest candidates were able to
f orm a correct conservation of momentum equation f or the components of momentum
perpendicular to the original path of P. Candidates in the middle of the ability range were of ten
conf used by the directions and tried to form an equation for the components parallel to the original
path of P. Typically these candidates assumed incorrectly that the initial velocity of P was zero and
so could make no progress.

Many candidates started with a symbol f ormula f or conservation of momentum such as

m1u1 + m2u2 = m1v 1 + m2v 2, but then jumped to a substitution that entirely neglected any masses,
and so worked exclusively in terms of velocity.

(ii) Nearly all candidates correctly gave an expression for kinetic energy. Weaker candidates typically
did not convert the mass of the alpha particle into kg, or used the mass of another particle. It was
common also f or candidates to f orget to square the velocity.

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 Cambridge International Advanced Subsidiary and Advanced Level
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PHYSICS

Paper 9702/23
AS Level Structured Questions 23

Key messages

• Candidates should pay attention to the instructions given in the question, particularly in explanatory
questions. If the question asks candidates to refer to a particular physical quantity, then not doing so is
unlikely to lead to full credit. Candidates should also be careful not to contradict statements given in the
question stem. For example, if intensity is stated to remain constant, then candidates who state that it
changes and rely on this in an explanation will not be awarded f ull credit.

• Candidates should avoid rounding intermediate answers in a numerical calculation as this can lead to an
incorrect final answer. Candidates should keep intermediate values in their calculators or record them to
several more significant figures than the final answer. Only once the f inal answer has been calculated
should this value be rounded to an appropriate number of signif icant f igures.

• Candidates should explicitly state the subject of any numerical or algebraic equations they use. This is
especially important where more than one equation is used in a question, and when equations are stated
and then rearranged. In some questions, credit can be awarded f or correct statements of physical
equations, but only where the whole equation is clearly known. Candidate should not rely on the
examiner to inf er a subject f or an expression given in the working.

• Candidates should pay attention to the units in which information is presented and take note of any SI
pref ixes.

General comments

Most candidates answered questions involving the recall and use of f ormulae well. Def initions were well
known by most, but many weaker candidates either missed out key words or used wording which changed
the meaning of the def inition.

In Question 3(b)(ii) and Question 5(b)(i), many candidates used the formula given on the question paper
but a significant number substituted inappropriate values f rom the data provided. Practice selecting the
relevant data to use with the given f ormula is essential.

There was no evidence that candidates were short of time on this paper.

Comments on specific questions

Question 1

There were many candidates who were unable to determine correct answers to this question as they
seemed to be unaware that the motion of the parcel could be treated as constant acceleration in the vertical
direction and constant speed in the horizontal direction.

(a) The majority of the candidates gave the correct definition of velocity. A f ew candidates gave just
‘velocity over time’ rather than ‘change in velocity over time’ and so could not be given credit. Some
gave ‘the rate of change of velocity per unit time’ which is a rate of a rate and so also incorrect.

(b) (i) Only the strongest candidates started the line horizontally from the base of the aircraf t to indicate
that the parcel started with zero vertical velocity. Many candidates gave a parabola with a vertical

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f inal section even though the question stated that there was no air resistance. There were many
straight diagonal and vertical lines indicating a lack of understanding of two -dimensional motion.
There were many other lines drawn f rom incorrect starting points such as the propeller of the
aircraf t or lines that started with too steep an angle.

(ii) The majority of the candidates used the concept that the vertical motion was at constant
acceleration due to free fall and correctly obtained the time f or the parcel to reach the ground. A
significant number ignored the vertical acceleration and used speed = distance / time, combining
the horizontal speed with the vertical distance.

(iii) The majority of the candidates used an equation of constant acceleration to determine the vertical
component of velocity. A significant number of candidates again attempted to obtain a value for the
f inal vertical velocity assuming no acceleration in the vertical direction.

(iv) This question was only answered well by the more able candidates. A significant number obtained
the correct value by combining the horizontal and vertical components of velocity. There were
many candidates that did not realise that the final vertical and horizontal components of velocity
needed to be combined to obtain the speed of the parcel.

Question 2

(a) The majority of candidates were able to give the idea of conservation of the total momentum. A
smaller number gave the correct condition that the conservation applies to an isolated system or
where there is no resultant external force. A significant number omitted the concept of the ‘sum of ’
or ‘total’ initial and f inal momentum.

(b) (i) This was very well done and generally well presented by the majority of the candidates.

(ii) The majority of the candidates calculated the change in kinetic energy. A small minority did not
convert the mass values given into kilograms. A small number calculated the total kinetic energy of
the two masses instead of the change in kinetic energy.

(c) (i) The stronger candidates calculated the rate of change of momentum of ball X to determine the
f orce on ball X. A significant number used the kinetic energy change incorrectly. A common error
was to f orget to convert the time given in ms into seconds. There were a number of ambiguous
answers given for the direction, such as ‘forwards’ or ‘east’, and a significant number of candidates
thought that the f orce acted to the lef t.

(ii) This question was answered well by the majority of the candidates. A small number of candidates
stated that the f orce would increase because of the larger mass of ball Y.

Question 3

(a) A signif icant number of candidates omitted the concept of ‘total’ or ‘sum of ’ the moments. A
common error was to give the definition of the moment of a f orce rather than to state the principle
of moments. Candidates are reminded to read the question caref ully.

(b) (i) The majority of the candidates gave at least one correct moment f or the three f orces acting. A
small number gave an answer using the values of the forces given in the question rather than using
the principle of moments.

(ii) The majority of the candidates calculated the area of the cylinder using the equation
upthrust = gV. A small number used an incorrect value f or the upthrust or were unable to link a
calculated volume to the cross-sectional area of the cylinder. A small number considered the
volume to be that of a sphere.

(c) This was a challenging question for many candidates. The majority drew a line starting f rom the
point (0.10, 0.40) given as the starting point in the question. The strongest candidates gave a
straight line with negative gradient ending with the correct h value. Many candidates appeared not
to f ully understand the physics of the situation (as the water was added, the upthrust increased and
a smaller moment was required from the load to achieve equilibrium, therefore x decreased). There

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were many straight lines with positive gradient, curves or lines that ended outside the possible
range f or h.

Question 4

(a) (i) Many candidates were not specific and did not state that the f orce needed to be applied on the
cross-sectional area.

(ii) The majority of the candidates gave the definition of strain. A significant number omitted ‘original’
f rom ‘original length’, giving only ‘extension over length’ which was not acceptable. There were
alternatives given for extension that were ambiguous such as ‘extension length’ which were also
not accepted. A small number gave the definitions for stress and strain the opposite way round.
Candidates are reminded to learn the def initions of key quantities within the syllabus.

(b) (i) Most candidates started with the equation for Young modulus. Many candidates used the f ull load
f or the force causing the extension of wire X, instead of only half the value of the load. A small
number of candidates did not convert the extension given in mm into m.

(ii) Most candidates explained that the cross-sectional area of wire Y would be larger and then
concluded that this meant a lower Young modulus for wire Y. Only the strongest candidates stated
that the f orce, extension and original length were the same for both wires to justify their conclusion
of a lower Young modulus for Y. A common response was for candidates to state that the Young
modulus was inversely proportional to the cross -sectional area. This was not suf f icient as an
explanation. A number of candidates stated that ‘other factors’ remained constant in addition to the
Young modulus being inversely proportional to the cross -sectional area, but this again was not
specif ic enough to be awarded credit f or the reasoning.

Question 5

(a) (i) The majority of the candidates knew the correct location f or a node and an antinode. Some
candidates drew their crosses clearly away from the line of the stationary wave. A f ew candidates
gave no labels to their crosses or reversed the positions of the antinode and node.

(ii) The majority of the candidates recognised that the stationary wave showed one and a half
wavelengths.

(iii) The majority of the candidates correctly calculated the frequency. A signif icant number could not
recall the wave equation correctly, or substituted an incorrect velocity or wavelength.

(b) (i) Most candidates were able to calculate the frequency using the Doppler equation given on the data
page of the question paper. A significant number calculated the minimum frequency instead of the
maximum frequency. It was clear that many weaker candidates did not know what the symbols in
the given equation represented.

(ii) The very strongest candidates gave a frequency variation that started at the source frequency then
continuously decreased to a minimum as the source moved away and continuously increased to a
maximum as it approached the observer, before returning to the source f requency as the source
returned.

Most candidates gave a steady decrease in the f requency to a minimum and no increase to a
maximum as the source approached the observer. The majority drew graphs that showed a
variation f or half a rotation only and many were an incorrect shape.

Question 6

(a) The majority of the candidates gave the correct def inition of resistance. A common error was to
give a definition that involved units such as ‘volt per current’ or ‘volt per ampere’, which could not
be given credit. Candidates are reminded that definitions of quantities should be given in terms of
other quantities.

(b) (i) Most candidates were able to correctly determine the value f or the resistivity.

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(ii) The majority of the candidates correctly determined the value for the charge. A common error was
to f orget to convert the time f rom minutes to seconds.

(iii) This was challenging f or many candidates. The most common error was to use the charge
calculated in (ii) instead of the elementary charge e. A small number f orgot to convert the speed
f rom mm s –1 to m s –1.

(c) (i) Many candidates could not give the correct symbol f or a thermistor. A small number gave the
correct symbol f or the thermistor, but omitted the f ixed resistor.

(ii) Stronger candidates gave a clear reasoning f or the power increasing in the f ixed resistor.
Candidates of ten stated that ‘the resistance’ would decrease but it was not clear whether this
meant the resistance of the thermistor or the f ixed resistor or the total resistance of the circuit.
Many candidates stated correctly stated that the current increased in the circuit but then concluded
that the power in the f ixed resistor decreased because the resistance had decreased.

Candidates’ responses indicated that they were often describing the changes to power dissipated
in other components of the circuit. Candidates are reminded to carefully read the question in order
to ensure that their answers are relevant.

Question 7

(a) This was straightforward for the majority of the candidates. Some candidates did not know the
charges on quarks, especially the strange quark.

(b) (i) This question was well answered by the majority of the candidates. The spelling of ‘hadron’ by a
number of candidates was often such that it was difficult to recognise. A common incorrect answer
was lepton.

(ii) This question was well answered by many candidates. It was common f or some answers to lack
suf ficient clarity, such as ‘the meson consists of two quarks’ and ‘baryons consist of three quarks
and three antiquarks’. Candidates are reminded to be precise in their descriptions.

(c) There were very f ew complete answers to this question. As the question asks for a description, the
names of the f undamental particles involved in + decay were required, rather than just their
symbols. Many candidates gave answers that involved protons and neutrons, but did not mention
the f undamental particles and so could not be given credit. The positron was rarely named as a
f undamental particle emitted with a neutrino.

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 Cambridge International Advanced Subsidiary and Advanced Level
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PHYSICS

Paper 9702/31
Advanced Practical Skills 31

Key messages

• If a raw value is out of trend to that expected, candidates should be encouraged to check the readings
again with the equipment provided in the early stages of data collection.

• Candidates should consider carefully whether it would be advantageous to repeat their measurements.

• In the table work, the number of significant figures in the calculated quantity should relate to the number
of significant figures in the raw data with the least number of significant figures. Each calculated quantity
should be checked row by row. It is unnecessary, and often incorrect, to force the number of signif icant
f igures to be constant down a column of calculated values.

• When justif ying a number of significant f igures in a calculated quantity, candidates should relate the
number of significant figures in the quantity to the raw readings used in the calculation. Candidates
should not use the phrase ‘raw readings’ without explaining what those readings are, or attempt to use
intermediate calculated quantities to justif y the number of signif icant f igures.

• To be successful answering Question 2, candidates should be reminded that their identified limitations
and suggestions f or improvement must be f ocused on the particular experiment being carried out.
General points such as ‘measurements were difficult’ or ‘use more precise measuring instrument s’ will
not usually gain credit without f urther detail.

General comments

Most centres did not have dif f iculties in providing the equipment requested. Any deviation between the
requested equipment and that provided to the candidates should be written down in the supervisor’s report,
and this report must be sent with the scripts to Cambridge so that the examiners can take this into
consideration when marking. No additional equipment should be available to the candidates. In some cases,
this may disadvantage candidates.

Any help given to a candidate should be noted on the supervisor’s report. Supervisors are reminded that
help should not be given with the recording of results, graphical work or analysis.

The general standard of the work done by the candidates was good, and there were many excellent scripts.
Candidates did not seem to be short of time and both questions were attempted by almost all the candidates.
They demonstrated good skills in the generation and handling of data but can improve by giving more
thought to the analysis and evaluation of experiments.

Comments on specific questions

Question 1

(a) Most candidates stated  in the accepted range and with an appropriate unit. A small number of
candidates stated a value of  that was out of range, suggesting that they had either misread the
protractor or not set up the apparatus correctly.

(b) Most candidates stated m in the accepted range, with an appropriate unit and to the correct
precision.

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(c) Most candidates correctly calculated e.

(d) Most candidates were able to collect six sets of values of M and  without assistance f rom the
supervisor and with the correct trend. Candidates are encouraged to check their results if any
values are out of trend with the rest.

Many candidates did not extend their range of M low enough and/or high enough. Candidates are
encouraged to use the whole range available to them.

Many candidates gave both the quantity and correct unit for each heading, separated by a solidus
or with brackets around the unit. Candidates are encouraged to remember to include a separating
mark between the quantity and unit. Some candidates gave the unit of sin  as ° (degree) instead
of leaving this calculated quantity without a unit.

Most candidates calculated values for sin  correctly. Candidates are encouraged not to truncate
the value without rounding.

Many candidates correctly stated their calculated values of sin  based on the number of
signif icant f igures used f or . Others gave too f ew or too many signif icant f igures.

(e) (i) Many candidates plotted the correct graph and labelled the quantities, and used sensible and
regular scales such that the data occupied over half the graph grid available. Plotting and reading
of points is then an easy task to carry out. Awkward or irregular scales were of ten the reason f or
not awarding credit f or the axes.

Many points were drawn as neat crosses such that the point centre was no more than half a square
thick, and were plotted correctly so that the position is within half a small square in both the x and y
directions. Common reasons for not awarding credit here were ‘b lobs’ (points with diameter greater
than half a small square) and points plotted more than half a square f rom the correct position.

(ii) Stronger candidates were able to draw a caref ully considered line of best f it with a balanced
distribution of points either side of the line along the entire length. Common reasons f or not
awarding this mark included lines needing a rotation or a shift to get a better fit and lines that were
kinked (two or more smaller lines joined up ).

If a point appears to be anomalous on the graph, candidates are encouraged to check their plotting
f irst, then check their reading with the equipment available. If the candidate still has one anomalous
point, they can identif y this point as such by ringing it or stating the point as ‘anomalous’.

(iii) Some candidates correctly used a large triangle to calculate the gradient, used correct read -of f s
and substituted into y / x correctly. Stronger candidates read off from the graph at x = 0 or used a
correct read of f into y = mx + c to f ind the y-intercept.

Common mistakes with the gradient were using too small a gradient triangle, substitution into
x / y, values incorrectly read off and points used from the table which were not on the line of best
f it. For the y-intercept, common mistakes were reading the y-intercept f rom the graph when there
was a f alse origin and substitution into a wrongly arranged equation e.g . c = y / mx.

(f) Stronger candidates recognised that P and Q were equal to the gradient and the y-intercept
respectively and stated correct units. Some candidates omitted units or used different units to those
used in the experiment without any evidence of converting correctly. Candidates who inverted their
axes on their graph (f rom the orientation requested in the question) generally did not go on to
rearrange the equation to be consistent.

Question 2

(a) Most candidates measured values of w and x in the accepted range and with a correct unit.

(b) (i) Many candidates correctly stated d in the accepted range and to the same precision as the ruler.
Some candidates incorrectly stated d to the nearest cm instead of mm, or their value was out of
range.

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 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

(ii) Some candidates, having repeated their readings, correctly showed the uncertainty working as half
the range and then went on to calculate the percentage uncertainty with the correct method. Others
made a realistic estimate of the uncertainty in d, taking into account the dif f icult nature of this
reading. Many candidates made too small an estimate of the absolute uncertainty in the value of d,
typically 0.1 cm.

(c) Many candidates recorded a value of T in the accepted range and some candidates repeated their
readings to gain maximum credit. Other candidates stated a period value that was out of range,
either because they did not divide by the number of oscillations they were measuring or they read
of f f rom the stopwatch incorrectly.

(d) The majority of the candidates stated a second value of d and T with the second T smaller than the
f irst value.

(e) (i) Most candidates were able to calculate k correctly. A minority rearranged the equation incorrectly.

(ii) Many candidates correctly justified the number of significant figures they had given for the value of
k with ref erence to the number of signif icant f igures used in T or time and d. Where candidates
were not successf ul, it was of ten because their answers were insuf f iciently detailed, e.g. ‘raw
readings’, ‘previous measurements’ or ‘values used in calculation’ without detailing the quantities
involved.

(f) Some candidates calculated the percentage difference between their values of k, tested it against
the stated 10% criterion and provided a valid statement. Some candidates omitted a percentage
dif ference calculation, gave a dif f erent criterion e.g. 15% or 20%, or gave an invalid statement
inconsistent with their findings.

(g) (i) Candidates need to identify problems associated with setting up and obtaining readings. They can
do this by writing about the dif f erent measurements taken or chronologically go ing through the
experiment systematically and identif ying each dif f iculty. Candidates should then try think of
solutions that address each problem.

Problems commonly awarded were ‘two sets of data were not enough to draw a valid conclusion’ ,
‘difficult to measure d as ruler not horizontal and ‘spring repeatedly rolled of f the board’. Many
candidates wasted options discussing the non-critical approximate measurements in the set-up
and/or measurements that were not dif f icult.

(ii) Improvements that were commonly seen were ‘take more readings and plot a graph’ and ‘use
video with a timer in the shot’. A solution, like the problem, needs detail to gain credit. Candidates
are encouraged to explain how a problem will be solved, detailing what additional equipment is
necessary.

Credit is not given for suggested improvements that could have been carried out in the original
experiment, e.g. ‘repeat readings’ or ‘view the ruler at right angles’.

© 2024
 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

PHYSICS

Paper 9702/33
Advanced Practical Skills 33

Key messages

• If a raw value is out of trend to that expected, candidates should be encouraged to check the readings
again with the equipment provided in the early stages of data collection.

• Candidates should consider carefully whether it would be advantageous to repeat their measurements.

• In the table work, the number of significant figures in the calculated quantity should relate to the number
of significant figures in the raw data with the least number of significant figures. Each calculated quantity
should be checked row by row. It is unnecessary, and often incorrect, to force the number of signif icant
f igures to be constant down a column of calculated values.

• When justif ying a number of significant f igures in a calculated quantity, candidates should relate the
number of significant figures in the quantity to the raw readings used in the calculation. Candidates
should not use the phrase ‘raw readings’ without explaining what those readings are, or attempt to use
intermediate calculated quantities to justif y the number of signif icant f igures.

• To be successful answering Question 2, candidates should be reminded that their identified limitations
and suggestions f or improvement must be f ocused on the particular experiment being carried out.
General points such as ‘measurements were difficult’ or ‘use more precise measuring instruments’ will
not usually gain credit without f urther detail.

General comments

Most centres did not have dif f iculties in providing the equipment requested. Any deviation between the
requested equipment and that provided to the candidates should be written down in the supervisor’s report,
and this report must be sent with the scripts to Cambridge so that the examiners can take this into
consideration when marking. No additional equipment should be available to the candidates. In some cases,
this may disadvantage candidates.

Any help given to a candidate should be noted on the supervisor’s report. Supervisors are reminded that
help should not be given with the recording of results, graphical work or analysis.

The general standard of the work done by the candidates was good, and there were many excellent scripts.
Candidates did not seem to be short of time and both questions were attempted by almost all the candidates.
They demonstrated good skills in the generation and handling of data but can improve by giving more
thought to the analysis and evaluation of experiments.

Comments on specific questions

Question 1

(a) Most candidates stated L and V in the accepted range and with an appropriate unit. Some
candidates stated a value of V that was out of range because they read the number as volts
instead of millivolts, e.g. 404 V instead of 0.404 V or 404 mV.

(b) Most candidates were able to collect six sets of values of L and V without assistance f rom the
supervisor and with the correct trend. Candidates are encouraged to check their results if one value
is out of trend with the rest.

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 Cambridge International Advanced Subsidiary and Advanced Level
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Principal Examiner Report f or Teachers

Many candidates did not extend their range of L values low enough and/or high enough.
Candidates are encouraged to use the whole range available to them.

Many candidates gave both the quantity and correct unit for each heading, separated by a solidus
or with brackets around the unit. Candidates are encouraged to remember to include a separating
mark between the quantity and unit. Some candidates omitted the unit or gave the unit of 1 / L as m
instead of m –1 (and similarly f or 1 / V).

Most candidates calculated values for 1 / V correctly. Candidates are encouraged not to truncate
the value without rounding.

Many candidates correctly stated their calculated values of 1 / V with a number of significant figures
consistent with those used f or V. Others gave too f ew or too many signif icant f igures.

The table work was done well by candidates in general. The most common mistakes were to use
too small a range and to use an incorrect number of signif icant f igures f or 1 / V.

(c) (i) Many candidates plotted the correct graph with quantities labelled, and used sensible and regular
scales such that the data occupied over half the graph grid available. Plotting and reading of points
is then an easy task to carry out. Awkward or irregular scales were of ten the reason f or not
awarding credit f or the axes.

Many points were drawn as neat crosses such that the point centre was no more than half a square
thick, and were plotted correctly so that the position is within half a small square in both the x and y
direction. Common reasons for not awarding credit here were ‘b lobs’ (points with diameter greater
than half a small square) and points plotted more than half a square f rom the correct position.

(ii) Stronger candidates were able to draw a caref ully considered line of best f it with a balanced
distribution of points either side of the line along the entire length. Common reasons f or not
awarding this mark included lines needing a rotation or a shift to get a better fit and lines that were
kinked (two or more smaller lines joined up ).

If a point appears to be anomalous on the graph, candidates are encouraged to check their plotting
f irst, then check their reading with the equipment available. If the candidate still has one anomalous
point, they can identif y this point as such by ringing it or stating the point as ‘anomalous’.

Candidates found drawing the line of best fit to be the most dif f icult part of the question, and in
general would benef it f rom more practice of this skill.

(iii) Some candidates correctly used a large triangle to calculate the gradient, used correct read -of f s
and substituted into y / x correctly. Stronger candidates read off from the graph at x = 0 or used a
correct read of f into y = mx + c to f ind the y-intercept.

Common mistakes with the gradient were using too small a gradient triangle, substitution into
x / y, values incorrectly read off and points used from the table which were not on the line of best
f it. For the y-intercept, common mistakes were reading the y-intercept f rom the graph when there
was a f alse origin and substitution into a wrongly arranged equation e.g . c = y / mx.

(d) Most candidates recognised that J and W were equal to the gradient and the y-intercept
respectively and stated correct units. Some candidates omitted units or used different units to those
used in the experiment without any evidence of converting correctly. Candidates who inverted their
axes on their graph (f rom the orientation requested in the question) generally did not go on to
rearrange the equation to be consistent.

(e) (i) Stronger candidates correctly read the micrometer scale with due regard to the precision and
stated correct units. Some candidates repeated their values of d to gain maximum credit. Many
candidates’ values were f ar f rom the expected value (and the supervisor’s value), suggesting
dif f iculty with using the micrometer.

© 2024
 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

(ii) The strongest candidates rearranged for a correct calculation of  with correct powers of ten. Many
weaker candidates did not convert to metres f or d and/or to metres in the unit f or J so that their
answer had a power-of -ten error.

Question 2

(a) Most candidates measured values of m to the nearest 0.1 g or better.

(b) (i) Stronger candidates correctly stated b and d to the same precision as the ruler and in the correct
range. Some candidates calculated (d − b ) with the correct unit. A common mistake was to omit
the unit or to give cm instead of cm 0.5 or √m.

(ii) Many candidates correctly justified the number of significant figures they had given for the value of
(d − b ) with ref erence to the number of signif icant f igures used in d and b or (d – b). Where
candidates were not successful, it was of ten because their answers were insuf f iciently detailed,
e.g. ‘raw readings’, ‘previous measurements’ or ‘values used in calculation’ without detailing the
quantities involved.

(iii) Many candidates stated H in the accepted range and the strongest candidates repeated their
readings to gain maximum credit.

(iv) Some candidates, having repeated their readings, correctly showed the uncertainty working as half
the range and then went on to calculate the percentage uncertainty with the correct method. Others
correctly estimated the uncertainty in H to be in the accepted range, taking into account the difficult
nature of this reading. Many candidates made too small an estimate of the absolute uncertainty in
the value of H, typically 0.1 cm or 0.2 cm.

(v) Many candidates calculated the value correctly.

(c) The majority of the candidates stated a second value of H and L with the second H greater than the
f irst value.

(d) Many candidates were able to calculate k for the two sets of data, showing their working clearly.
Some candidates had different values of M and m f or the f irst k value when these should have
been the same. A small number of candidates incorrectly stated their values to one signif icant
f igure.

(e) Stronger candidates calculated the percentage dif f erence between their values of k, tested it
against the stated 15% criterion and provided a valid statement of conclusion. Some candidates
omitted a percentage difference calculation, gave a different criterion e.g. 10% or 20%, or gave an
invalid statement inconsistent with their f indings.

(f) (i) Candidates need to identify problems associated with setting up and obtaining readings. They can
do this by writing about the dif f erent measurements taken or chronologically go ing through the
experiment systematically and identif ying each dif f iculty. Candidates should then try think of
solutions that address each problem.

Problems commonly awarded were ‘two sets of data were not enough to draw a valid conclusion’ ,
‘difficult to measure b as difficult to identify the centre of the ball, ‘H difficult to measure as dif f icult
to know when reaches maximum height’. Many candidates wasted options discussing the non-
critical approximate measurements in the experimental set-up such as the 50 cm and 1.5 cm
lengths and/or measurements that were not at all dif f icult, such as d.

(ii) Improvements that were commonly seen were ‘take more readings and plot a graph’ and ‘use
video and a ruler in the shot to measure the maximum height H’. A solution, like the problem,
needs detail to gain credit. Candidates are encouraged to explain how a problem will be solved,
detailing what additional equipment is necessary.

Credit is not given for suggested improvements that could have been carried out in the original
experiment, e.g. ‘repeat readings’ or ‘view the ruler at right angles’.

© 2024
 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

PHYSICS

Paper 9702/34
Advanced Practical Skills 34

Key messages

• If a raw value is out of trend to that expected, candidates should be encouraged to check the readings
again with the equipment provided in the early stages of data collection.

• Candidates should consider carefully whether it would be advantageous to repeat their measurements.

• In the table work, the number of significant figures in the calculated quantity should relate to the number
of significant figures in the raw data with the least number of significant figures. Each calculated quantity
should be checked row by row. It is unnecessary, and often incorrect, to force the number of signif icant
f igures to be constant down a column of calculated values.

• When justif ying a number of significant f igures in a calculated quantity, candidates should relate the
number of significant figures in the quantity to the raw readings used in the calculation. Candidates
should not use the phrase ‘raw readings’ without explaining what those readings are, or attempt to use
intermediate calculated quantities to justif y the number of signif icant f igures.

• To be successful answering Question 2, candidates should be reminded that their identified limitations
and suggestions f or improvement must be f ocused on the particular experiment being carried out.
General points such as ‘measurements were difficult’ or ‘use more precise measuring instruments’ will
not usually gain credit without f urther detail.

General comments

Most centres did not have dif f iculties in providing the equipment requested. Any deviation between the
requested equipment and that provided to the candidates should be written down in the supervisor’s report,
and this report must be sent with the scripts to Cambridge so that the examiners can take this into
consideration when marking. No additional equipment should be available to the candidates. In some cases,
this may disadvantage candidates.

Any help given to a candidate should be noted on the supervisor’s report. Supervisors are reminded that
help should not be given with the recording of results, graphical work or analysis.

The general standard of work carried out by the candidates was good, with some producing excellent scripts.
Where candidates performed less well, this was often due to improper presentation of data, e.g. the omission
of units with values.

Working was usually clear and legible, but some candidates should be reminded to draw tables caref ully
using ruled lines and, where possible, record data systematically. Candidates are also advised to leave a
small gap between a value of time and the unit ‘s’. Some wrote the unit in such a way that it was dif f icult to
determine whether a unit had been stated or if ‘5’ was the f inal digit of their value.

The independent variable f or the experiment in Question 1 was the height above the bench of a scale
marking on the syringe. Candidates should be aware that the examiners will check that the values of the
independent variable dif f er f rom each other. Duplicated values will only count as one reading.

For graph work, candidates should be encouraged to use a 30 cm ruler to draw lines of best fit and to provide
legible, sensible scale markings on axes. Candidates selecting sensible scales are much less likely to make
errors when plotting points and taking read -of f s f or the gradient and intercept calculations.

© 2024
 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

Comments on specific questions

Question 1

(a) (i) The majority of the candidates provided values of ht and hb that were in the accepted range and
with an appropriate unit (e.g. cm). Some candidates had values outside of range but within
tolerance of the supervisor’s value and so were still able to gain credit. Some candidates did not
provide a unit.

(ii) A signif icant number of candidates misread stopwatches. Some, af ter taking a sensible
measurement of time, divided their value by, for example, 10. This was possibly to account f or the
number of intervals between the scale markings. This action was incorrect and always resulted in a
f inal answer outside of the accepted range, so the candidate did not gain credit.

Credit was available for repeated readings. When measuring time, especially where timings are
short, it is good practice to take multiple readings. Most candidates did this.

(b) The majority of the candidates successf ully f ollowed the instructions and recorded six sets of
values of ht, hb and T. The most successf ul candidates presented their data sequentially and
ensured that the f ull range of possible ht values was included in their data.

Credit f or the range of values was awarded if the difference between the candidate’s maximum and
minimum values of ht was greater than 5 cm. Many candidates achieved this.

Column headings in the table were usually correct and included a suitable separator between the
quantity and unit. Candidates who were not awarded credit of ten f ound it dif f icult to provide a
suitable unit f or the 1 / T value.

When recording the heights ht and hb, candidates were expected to present their data using
appropriate and consistent precision. Many did this by recording all values to the nearest mm.

The calculation of 1 / T was correct in most cases. A small number of candidates gave a value that
was incorrectly rounded.

Most candidates recognised the need to present 1 / T values to the same number of signif icant
f igures as (or one more than) than the number of signif icant f igures in the corresponding raw T
values.

(c) (i) Candidates producing successful graphs did so by choosing sensible scales that allowed plotted
points to occupy at least 4 large squares horizontally and 6 large squares vertically. Scale markings
were generally clear, and values were usually written one large square apart.

Some candidates selected unsuitable scales, e.g. labelling axes using f ractions or by calculating
the dif ference between their minimum and maximum table values and dividing by the number of
squares available on the grid. Awkward scales, including the examples mentioned, should be
heavily discouraged as candidates often make subsequent errors when taking read -of f s and may
be unable to gain credit in multiple dif f erent places as a result.

Whilst the plotting of points was generally accurate, some candidates used large circles as points
making it impossible to judge whether the points were accurate to within half a small square. These
are not given credit.

(ii) When drawing the straight line of best fit, many candidates produced thin lines that had an even
distribution of points either side of the line along the f ull length. Common reasons f or lines not
being given credit were broken or kinked lines, possibly as a result of using short rulers, or lines
requiring a rotation.

Candidates should be made aware that, if they identify a point as anomalous and decide to ignore
it when drawing the line, they need to indicate this by either circling the point or labelling it. Only
one anomaly can be ignored. If a candidate circles two or more points, the examiner will consider
all points when judging the line.

© 2024
 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

(iii) Most candidates correctly read off two points from their line that were at least half the length of the
line apart and then substituted points into the equation y / x or equivalent. Some candidates
incorrectly used x / y or used points in their equation that were not on the line of best f it.

For the y-intercept, most candidates correctly substituted values into y = mx + c or equivalent. A
common error made by candidates was in taking a direct read-off from the graph as the y-intercept
despite the x-axis having a f alse origin.

(d) Most candidates recognised that p was equivalent to their gradient value and q was equivalent to
their y-intercept value. Units were often provided, but these were not always consistent with the
readings, e.g. candidates working in cm but giving the unit s –1 m–1 f or p.

Question 2

(a) (i) Most candidates stated a value for r within the expected range and measured to the nearest mm.
Some candidates had values outside the accepted range, were still awarded credit if the
unexpected r value was within tolerance of the supervisor’s value of r.

(ii) The value of x stated by most candidates was smaller than 15 cm.

Credit was available for the taking of repeated readings. Many candidates did not choose to repeat
their measurements. Candidates should be advised to take repeated readings where appropriate,
e.g. when taking measurements of a dynamic system such as this.

(iii) When asked to estimate the percentage uncertainty in x, successful candidates chose an absolute
uncertainty in the range 0.3–1.0 cm. They then divided the absolute uncertainty by their x value
bef ore multiplying the result by 100. Others derived the absolute uncertainty from half the range of
their repeated readings. This was credited when the working was clearly shown.

Many of the candidates who did not gain credit simply stated the resolution of the rule (0.1 cm) as
their absolute uncertainty. Given the nature of the experiment (x was measured while the magnet
was moving and at a significant distance above the rule), this was deemed an unrealistic estimate
of the absolute uncertainty. Candidates should be encouraged to think about the inherent dif f iculty
in taking the measurement as well as the precision of the measuring instrument.

(iv) Most candidates were able to correctly calculate h.

(b) Almost all candidates provided second values of x and h. Some candidates found that the second
value of x (heavier nut) was not smaller than the first value of x, suggesting that they had not set up
the apparatus correctly.

(c) (i) Most candidates were able to correctly calculate two values of k. A small number of candidates
inappropriately rounded their f inal value(s) to one signif icant f igure.

(ii) Some candidates successfully linked the signif icant f igures in k with those in (M + m) and h. A
significant number ref erred only to ‘raw data’ or made a partial reference to the correct quantities.

Candidates should not make a general statement such as ‘the quantity with the least signif icant
f igures’. Candidates are expected to state all quantities that should be considered when deciding
on the suitable number of signif icant f igures.

(d) Candidates were provided with a numerical criterion of 15% to test against. To be successf ul, they
needed to carry out a correct percentage difference calculation, a comparison with 15%, and then
give a correct conclusion linking both. The strongest candidates were able to correctly carry out a
suitable percentage difference calculation, but many weaker candidates were not. A small number
of candidates made incorrect conclusions, e.g. ‘my values do not support the suggested
relationship as the percentage difference between the values of k is only 3% which is not close to
15%’.

A small number of candidates tested against their own criterion, e.g. 10%, and were not credited.

© 2024
 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

(e) (i) Most candidates recognised that there were too few data to draw a conclusion and that there were
sometimes problems with the magnet picking up the nut. Other marking points were, in general,
less well addressed.

Centres should encourage candidates to follow the instructions and always state the quantity being
measured along with the reason for the uncertainty, e.g. ‘it was diff icult to measure r because…’.
Many candidates recognised limitations but did not link these to the correct quantity. For example,
some candidates stated that the centre of the magnet was hard to determine but they did not link
this to the measurement of r.

(ii) Most candidates recognised the need f or more data so that a graph could be plotted. Other
common correct suggestions were clamping the rule (when measuring r), using stronger magnets
(to increase the chances of picking up the nut) and using a vertical reference at the 15 cm mark (to
ensure a consistent starting point).

Although many candidates referenced the use of video to capture the measurement of x, many did
not include a ruler in view. Instead, many ref erred incorrectly to including a timer or watching
f rame-by-f rame.

Candidates should be aware that the examiners do not look f or links between responses in the
limitations section and those in the improvements section. As such, candidates should state any
apparatus/quantity in (ii) and avoid using phrases such as ‘clamp it’ assuming that the examiner
knows what ‘it’ is because of working f rom (i).

© 2024
 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

PHYSICS

Paper 9702/35
Advanced Practical Skills 35

Key messages

• If a raw value is out of trend to that expected, candidates should be encouraged to check the readings
again with the equipment provided in the early stages of data collection.

• Candidates should consider carefully whether it would be advantageous to repeat their measurements.

• In the table work, the number of significant figures in the calculated quantity should relate to the number
of significant figures in the raw data with the least number of significant figures. Each calculated quantity
should be checked row by row. It is unnecessary, and often incorrect, to force the number of signif icant
f igures to be constant down a column of calculated values.

• When justif ying a number of significant f igures in a calculated quantity, candidates should relate the
number of significant figures in the quantity to the raw readings used in the calculation. Candidates
should not use the phrase ‘raw readings’ without explaining what those readings are, or attempt to use
intermediate calculated quantities to justif y the number of signif icant f igures.

• To be successful answering Question 2, candidates should be reminded that their identified limitations
and suggestions f or improvement must be f ocused on the particular experiment being carried out.
General points such as ‘measurements were difficult’ or ‘use more precise measuring instruments’ will
not usually gain credit without f urther detail.

General comments

Most centres did not have difficulties in providing the equipment requested. In Question 1 there was some
variation in the mass of the rulers provided to candidates which affected the balance point. These variations
were accommodated within the marking process to allow all candidates fair access to the marks for this part
of the experiment.

Any deviation between the requested equipment and that provided to the candidates should be written down
in the supervisor’s report, and this report must be sent with the scripts to Cambridge so that the examiners
can take this into consideration when marking. No additional equipment should be available to the
candidates. In some cases, this may disadvantage candidates.

Any help given to a candidate should be noted on the supervisor’s report. Supervisors are reminded that
help should not be given with the recording of results, graphical work or analysis.

The general standard of the work done by the candidates was good, and there were many excellent scripts.
Candidates did not seem to be short of time and both questions were attempted by almost all the candidates.
They demonstrated good skills in the generation and handling of data but could improve in two main areas:
f irstly by ensuring that the presentation of their work is legible and conf orms to scientif ic convention (f or
example, the layout of the table in Question 1 using ruled lines and clear headings) and secondly, in the last
part of Question 2, by being more specif ic about how their limitations and improvements relate to the
quantities being measured.

© 2024
 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

Comments on specific questions

Question 1

(a) Most candidates had appropriate values f or a and s and with s greater in value than a.

(b) Most candidates were able to collect six sets of values of a and s without assistance f rom the
supervisor and obtained the correct trend. Candidates are encouraged to check their results if one
value is out of trend with the rest and to repeat the collection of that data set.

Some candidates did not extend their range to a value that was low enough and/or high enough.
Candidates are encouraged to use the whole range available to them.

Many candidates gave both the quantity and correct unit for each heading, separated by a solidus
or with brackets around the unit. Candidates are encouraged to remember to use a separating
mark between the quantity and unit. Some candidates incorrectly gave the unit of s / a as m or m–1.

Many candidates correctly wrote their calculated values of s / a to a suitable number of signif icant
f igures based on their values of a and s. Candidates are encouraged to be aware that changes in
the number of significant figures in their raw (collected) data can have an ef f ect on the number of
significant figures in their calculated values. This occurs when the collected data spans both single-
digit and double-digit numbers.

Most candidates calculated values for s / a correctly. Candidates are encouraged not to truncate a
value without correct rounding.

Overall, the table work was done well by candidates, but many candidates could have improved by
having clearer presentation. Candidates are encouraged to take the time to construct a clear, well
laid out table in which to record their data.

(c) Many candidates plotted the correct graph with quantities labelled, and used sensible and regular
scales such that the data occupied over half the graph grid available. Plotting and reading of points
is then an easy task to carry out. Awkward or irregular scales were of ten the reason f or not
awarding credit f or the axes.

Many points were drawn as neat crosses such that the point centre was no more than half a square
thick, and were plotted correctly so that the position is within half a small square in both the x and y
direction. Common reasons for not awarding credit here were ‘b lobs’ (points with diameter greater
than half a small square) and points plotted more than half a square f rom the correct position.
Candidates are encouraged to use a sharpened pencil f or the graph work.

(ii) Stronger candidates were able to draw a caref ully considered line of best f it with a balanced
distribution of points either side of the line along the entire length. Common reasons f or not
awarding this mark included lines needing a rotation or a shift to get a better fit and lines that were
kinked (two or more smaller lines joined up, sometimes made using a damaged straight edge).

If a point appears to be anomalous on the graph, candidates are encouraged to check their plotting
f irst, then check their reading with the equipment available. If the candidate still has one anomalous
point, they can identif y this point as such by ringing it or stating the point as ‘anomalous’.

(iii) Some candidates correctly used a large triangle to calculate the gradient, used correct read -of f s
and substituted into y / x correctly. Stronger candidates read off from the graph at x = 0 or used a
correct read of f into y = mx + c to f ind the y-intercept.

Common mistakes with the gradient were using too small a gradient triangle, substitution into
x / y, values incorrectly read off and points used from the table which were not on the line of best
f it. For the y-intercept, common mistakes were reading the y-intercept f rom the graph when there
was a f alse origin and substitution into a wrongly arranged equation e.g . c = y / mx.

(d) (i) The majority of the candidates correctly identified P as being the gradient and Q the y-intercept. A
signif icant number of candidates did not give a unit with the value of P.

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(ii) Stronger candidates correctly rearranged the equation and found a value f or R. Many candidates
identif ied the correct unit f or R (g) but weaker candidates of ten either had no unit or some
combination of g and cm (e.g. g cm–2).

Question 2

(a) (i) Many candidates correctly measured values of L and d and did so to an appropriate precision.
Weaker candidates did not use the micrometer to measure d or, in some cases, misread the
micrometer. Stronger candidates measured multiple values of d along the rod and calculated an
average value. In general, candidates need to be mindful that repeating readings is appropriate f or
measured quantities in which variation of values might be obtained if doing the experiment again or
if done by another experimenter.

(ii) Stronger candidates correctly justified the number of significant figures they had given for the value
of V with reference to the number of significant figures used in d and L. A common reason for credit
not being awarded was undetailed reference to ‘raw readings’, ‘previous measurements’ or ‘values
used in the calculation’ without giving the individual raw quantities concerned. Some candidates
incorrectly f ocused on the number of decimal places involved in the data.

(b) (i) Most values of S0 were in the accepted range. Some weaker candidates did not convert correctly
f rom a measurement in cm to a value in m.

(ii) Some candidates, having repeated their readings, correctly showed the uncertainty working as half
the range and then went on to calculate the percentage uncertainty using a correct method. Others
correctly estimated an uncertainty in S0 that was reasonable, taking into account the dif f iculties of
taking this reading using a (long) ruler. Weaker responses had a vague or unclear use of a half -
range calculation (e.g. not showing the data on which this was based), or had power-of -ten errors
in the absolute uncertainties (e.g. 0.02/0.050 instead of 0.002/0.050).

(iii) This was done correctly by the majority of the candidates.

(c) Candidates were expected to record the time taken for at least 5 oscillations, and to do this at least
twice bef ore using their measurements to determine an average f or their f inal value. Many
candidates did this clearly and accurately. Candidates who did not gain credit typically measured
the time f or one oscillation three or four times before averaging, or measured a single value of , f or
example, 10T only. Some candidates correctly measured, f or example, three values of 10T, but
then only divided their total value by 3, and did not also divide by 10. This was not able to gain
credit. A minority of candidates also calculated n / nT rather than nT / n, which was also unable to
gain credit, as was misreading the stop watch to give times such as 0.0004 s.

(d) The majority of the candidates successfully made two further readings of M and T and also showed
good experimental technique in obtaining a second value of T that was larger than the f irst.

(e) Many candidates were able to calculate  for their two sets of data, showing their working clearly.
Weaker candidates rearranged the equation incorrectly (e.g.  = kT2 / 42V – M) and so obtained
an incorrect value for . A minority of candidates incorrectly stated their values of  to only one
signif icant f igure.

(f) Stronger candidates calculated the percentage dif f erence between their values of , tested it
against the stated 15% criterion and provided a valid statement of conclusion. Some candidates
omitted a percentage dif f erence calculation, gave a dif f erent criterion (e.g. 10%, 20% or the
uncertainty f rom (b)(ii)) or gave a statement that was inconsistent with their f indings. Some
candidates also conf used ‘percentage dif f erence’ with ‘percentage uncertainty’ meaning their
conclusion was unclear. A minority of candidates were not awarded credit because they attempted
to calculate their own percentage uncertainty using estimates of the uncertainty in V, T or M.

(g) (i) Candidates need to identify difficulties associated with setting up and obtaining readings. They can
do this by writing about the dif f erent measurements taken or chronologically going through the
experiment systematically. Candidates should then think of corresponding solutions that address
each dif f iculty.

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Problems commonly awarded credit were: ‘two sets of data were not enough to draw a valid
conclusion’, ‘difficult to measure T as it is difficult to identify the start (or end) of an oscillation’ and
‘S0 was dif f icult to measure because of parallax error (f rom the curvature of the rods)’.

(ii) Improvements that were commonly credited included ‘take more readings and plot a graph’ and
‘clamp the ruler when measuring S0’.

In general, with both limitations and improvements, candidates should be encouraged to state what
the problem is and give a reason for it, e.g. ‘it is difficult to measure T because it is difficult to judge
the start/end of an oscillation’. For improvements, candidates should state the solution and say how
this helps solve a specific problem, e.g. ‘take a video with a timer in view to help obtain a more
accurate value of T’.

Credit is not given for suggested improvements that could have been carried out in the original
experiment, e.g. ‘repeat readings’ or ‘view the ruler at right angles’.

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PHYSICS

Paper 9702/36
Advanced Practical Skills 36

Key messages

• If a raw value is out of trend to that expected, candidates should be encouraged to check the readings
again with the equipment provided in the early stages of data collection.

• Candidates should consider carefully whether it would be advantageous to repeat their measurements.

• In the table work, the number of significant figures in the calculated quantity should relate to the number
of significant figures in the raw data with the least number of significant figures. Each calculated quantity
should be checked row by row. It is unnecessary, and often incorrect, to force the number of signif icant
f igures to be constant down a column of calculated values.

• When justif ying a number of significant f igures in a calculated quantity, candidates should relate the
number of significant figures in the quantity to the raw readings used in the calculation. Candidates
should not use the phrase ‘raw readings’ without explaining what those readings are, or attempt to use
intermediate calculated quantities to justif y the number of signif icant f igures.

• To be successful answering Question 2, candidates should be reminded that their identified limitations
and suggestions f or improvement must be f ocused on the particular experiment being carried out.
General points such as ‘measurements were difficult’ or ‘use more precise measuring instruments’ will
not usually gain credit without f urther detail.

General comments

Most centres did not have dif f iculties in providing the equipment requested. Any deviation between the
requested equipment and that provided to the candidates should be written down in the supervisor’s report,
and this report must be sent with the scripts to Cambridge so that the examiners can take this into
consideration when marking. No additional equipment should be available to the candidates. In some cases,
this may disadvantage candidates.

Any help given to a candidate should be noted on the supervisor’s report. Supervisors are reminded that
help should not be given with the recording of results, graphical work or analysis.

The general standard of the work done by the candidates was good, and there were many excellent scripts.
Candidates demonstrated good skills in the generation and handling of data but can improve by giving more
thought to the analysis and evaluation of experiments.

Working was usually clear and legible, but some candidates should be reminded to draw tables caref ully
using ruled lines and, where possible, record data systematically. Candidates are also advised to leave a
small gap between a value of time and the unit ‘s’. Some wrote the unit in such a way that it was dif f icult to
determine whether a unit had been stated or if ‘5’ was the f inal digit of their value.

Candidates did not seem to be short of time and both questions were attempted by almost all the candidates.
Candidates should be reminded that they are only allowed access to apparatus f or each question f or one
hour and should allocate their time within each question accordingly.

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Comments on specific questions

Question 1

(a) Some candidates did not provide a unit for the length x. The metre rule can be read to the nearest
0.1 cm. The protractor can only be read to the nearest degree.

(b) Most candidates were able to obtain the required six sets of values, with the correct trend. There
were some candidates who only increased (or decreased) their x values from the starting value in
(a) and so did not cover the full range of values that was available to them. Candidates should be
reminded that the widest possible range of the independent variable should be used. In this case,
candidates should be able to have x values from close to zero to over 26 cm but allowance was
made f or dif f iculties making the holes in the card.

Some candidates improved the quality of their results by taking repeated values of  for each value
of x and calculating a mean value; this should be recognised as good practice.

The most common errors in table headings were giving a unit for 1 / tan  or missing a separating
mark between  and °.

Recording values of x to the nearest mm was usual, with many candidates having all zeros in the
mm place. This is acceptable in this case as candidates are choosing their values of x, but
measurements of length in other contexts are unlikely to all end in .0 cm. Some candidates added
an extra 0 af ter the decimal point for x values less than 10 cm, presumably to give these values to
3 signif icant f igures. This is incorrect as these are measured, not calculated , values.

Values of 1 / tan  were usually calculated correctly and given to an acceptable number of
significant figures. Candidates with values of  less than 10° (1 significant f igure) should not give
values of 1 / tan  to 3 signif icant f igures. This was a case where candidates need to check
significant figures in calculated quantities for each row of their table, rather than down a column.

(c) (i) Most candidates gained credit f or drawing appropriate axes, with labels and sensible scales
covering at least half the graph grid, and plotting their six points accurately.

With typical x values in the range 4–28 cm, some candidates were tempted to use a scale based
on 3 f or each large square. Although this appears to give a good spread of points, it is not
acceptable as the scale is very difficult to use. Errors in plotting or reading values f rom the graph
were very common with awkward scales.

If candidates identify an anomalous point, they should first check the plotting of that point, then the
calculation and then, if possible, to use the apparatus to repeat the measurements for that point. If
necessary, a single anomalous point can be indicated and ignored when drawing the line of best fit.

(ii) Many candidates were able to draw a straight line of best f it. A large number of lines required
rotation to give a good spread of points along the line. Some lines seemed to have been drawn so
that the maximum number of plotted points were on the line and points not on the line were
ignored. A significant number of lines were drawn in two sections, or distorted at one end, so that
the line was kinked. Candidates should use a transparent, non-folding 30 cm ruler to draw a single,
clear line.

(iii) Candidates can either draw a triangle on their line or indicate two points on the line used to
determine the gradient. To avoid confusion, these points should not be indicated with the same
type of crosses as the plotted points.

There were cases of incorrect read-offs substituted into the gradient calculation, particularly when
awkward scales were used. Candidates should be encouraged to use one of the gradient read-offs
substituted into the equation for intercept, rather than using another point which creates a f urther
chance of reading error. A common mistake was to use values from the table f or a point that was
not on the line.

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(d) The majority of the candidates transf erred their gradient and y-intercept values as a and b
respectively. In general, candidates should be advised that they should not present their f inal
answers to only one signif icant f igure.

Candidates who considered the units for the gradient and y-intercept were able to give the correct
unit f or a. Otherwise, candidates can ensure that each term in the equation has a consistent unit –
in this case ax must have no unit so a must be in cm –1 if x is given in cm.

Question 2

(a) A small number of candidates recorded the circle radius rather than diameter. Candidates should
be advised that it is good practice to repeat and average diameter measurements, although in this
case it was not critical as the centre of the circle was known. The use of a 30 cm ruler means that
all values should be to the nearest millimetre and the average value should have the same number
of signif icant f igures.

(b) (i) Some candidates gave their value of p to the nearest centimetre, despite using a ruler with a
millimetre scale.

(ii) Candidates who took repeated readings for p in (i) were usually able to successf ully determine a
percentage uncertainty using the half-range method. Otherwise, absolute uncertainties of 1 mm or
1 cm were common, neither of which were reasonable estimates.

(c) (i) Despite the unfamiliar motion, many candidates were able to obtain a suitable value for the period
of rotation. Units were omitted by some candidates. A significant number of candidates recorded
only a single value of T, or repeated values for one rotation. It is good practice to repeat any timing
measurement and to determine the time f or multiple cycles. Stronger candidates measured the
time f or 10 rotations three times, giving a total time of about 25 s.

(ii) The calculation caused little dif f iculty and there were very f ew rounding errors.

(d) Almost all candidates were able to determine a shorter period for the shorter conical pendulum, as
expected. There were some answers where the period was only given to one signif icant f igure.

(e) (i) Values of k were usually calculated correctly. In a small number of cases, the value was only given
to one signif icant f igure, possibly due to rounding of the previous period value.

(ii) The justif ication for the number of significant figures needs to be based on the raw data used to
determine that value. It is insuf f icient to state ‘raw data’ or ‘raw readings’, and this was seen in
many answers. In this experiment, the values of D and p were the raw data used to calculate  and
measured times were used to calculate T. These need to be stated explicitly, such as ‘the diameter
D and length of pendulum p were determined to 3 significant figures, the times were measured to
only 2 significant figures so the value of k can be given to 2 significant figures, the lowest of these’.
Other options were also given credit in this case, including , p and T.

(f) Candidates should calculate the percentage difference between their k values and compare this to
the suggested percentage uncertainty. There was a large number of clear answers but some vague
statements such as, ‘the percentage uncertainty was less than the percentage uncertainty, so the
results support the relationship ’. Candidates should make a numerical comparison with the
suggested uncertainty given, in this case 15%. Some weaker candidates mistakenly suggested that
the relationship was supported if the percentage dif f erence was equal to 15%.

(g) (i) Most candidates described four sources of uncertainty or problems, but many suggestions were too
vague or did not refer to the measurement affected. Difficulty judging the position of the centre of
the bob needed to be linked to the measurement of p, f or example.

A large number of responses referred to the difficulty measuring or maintaining the 5 mm above the
cross, although this is irrelevant once the bob is in its circular motion. In this experiment , it is
necessary to move the knot in small circles to maintain the circular motion, so problems stat ing
about the dif f iculty of holding the knot stationary were not relevant.

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Many candidates recognised that two sets of data were insuf f icient to draw a valid conclusion.
There were some clear statements regarding dif f iculty in timing where candidates used their
experience of other oscillatory motion.

(ii) Most candidates described four improvements but, as with the problems in (i), there were many
incomplete answers. There were also many suggestions such as ‘read the ruler at right angles’,
‘take repeat measurements and calculate the average’ or ‘time multiple rotations of the bob ’ that
are standard practice and are not given credit.

Stronger candidates were able to suggest taking more sets of readings and plotting a graph, and
taking a video with a timer in view and replaying f rame by f rame.

The key to this section is for candidates to identify genuine problems associated with setting up the
experiment and in obtaining measured values. Candidates are then encouraged to suggest
practical solutions that either improve technique or give more reliable data. More successf ul
candidates will select relevant problems and describe them clearly, linking to relevant
measurements and will suggest improvements that are workable and expressed clearly.

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PHYSICS

Paper 9702/41
A Level Structured Questions 41

There were too f ew candidates f or a meaningf ul report to be produced.

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PHYSICS

Paper 9702/42
A Level Structured Questions 42

Key messages

• It is important that candidates use technical language accurately. Examples of words that are of ten
conf used by candidates are atom and molecule, nuclide and nucleus, and force and f ield. Candidates
are not able to obtain full credit if they use an inappropriate word that makes the response technically
incorrect.

• In def ining quantities, candidates need to take care to ensure that the def inition they give is
dimensionally correct. This often requires use of the phrase ‘per unit’ where the quantity being def ined
is the ratio between two other quantities, or ‘product’ where the quantity being def ined is two other
quantities being multiplied together. Examiners will only consider symbol equations to be part of a
def inition if the symbols used are identif ied.

• Candidates need to take care to ensure that they read the question properly, understand what is being
asked and give responses that answer the question that is asked. It is not uncommon to f ind
candidates giving answers to questions that were not asked, but that have been asked in recent past
papers. Candidates should be advised not to rely heavily on memorising previous mark schemes.

• When answering questions involving calculations, it is important for candidates to show their reasoning
clearly. This includes taking care to use the correct conventional symbols f or physical quantities. If
working is clear and based on use of correct physics, it is often possible for examiners to award partial
credit even when the final answer is incorrect. Incorrect answers that are not supported by working
cannot be awarded credit.

• Answers to numerical questions should be given to an appropriate number of signif icant f igures; the
precision of the data provided in the question is generally indicative of the appropriate number of
signif icant f igures f or an answer. When perf orming intermediate calculations within a question,
candidates should take care to avoid premature rounding; as a general rule, any intermediate calculated
values should always carry at least one more signif icant f igure than will be used in the f inal answer.
Candidates should be made aware that giving answers to an inappropriate number of significant figures,
or that are inaccurate as a result of rounding intermediate values prematurely, can both lead to f ull
credit not being awarded.

General comments

The question paper contained questions of a variety of levels of diff iculty, enabling candidates at dif f erent
levels of ability to show what they know. Candidates who knew the ‘bookwork’, read the questions caref ully,
took care over their use of technical language and answered the questions asked were able to perform well.

Some candidates use up more than half of the space provided for the answer by starting their response with
essentially a re-write of the question. Candidates should be advised not to do this, as it wastes time and uses
up answer space, and cannot lead to any credit being awarded.

Candidates need to be careful that they do not give more than one answer to a question. This is particularly
important when they are answering a question that asks for the definition of a quantity or the meaning of a
symbol. These things only have one answer. If multiple answers are provided that are contradictory, the
candidate cannot be awarded credit f or a correct answer.

There was no evidence that candidates had insuf f icient time in which to complete the paper.

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Comments on specific questions

Question 1

(a) (i) This question and (ii) were generally well answered by candidates that knew the basic equations
f or centripetal acceleration.

(ii) Some candidates who calculated the correct acceleration made an arithmetic error in rounding, to
get a f inal answer of 1.6  104 m s –2.

(b) (i) Lenz’s law was only well known by the strongest candidates. To be awarded credit, candidates first
needed to make it clear that Lenz’s law is to do with the direction of the induced e.m.f . Conf usion
with Faraday’s law was common, with many candidates giving responses in terms of the magnitude
of the induced e.m.f .

(ii) This question was generally well answered, with most candidates able to show successf ully that
the period is 45 ms.

(iii) Many candidates knew the defining equation for magnetic flux. Some candidates did not know the
correct formula for the area of a circle. Other candidates incorrectly included a f actor of  8 in the
calculation.

(iv) Many candidates were awarded credit f or realising that the magnitude of the e.m.f . is given by
Faraday’s law, but  8 f actors were common here too. Candidates should realise that the spokes
are ef fectively in parallel, not in series, and so the  8 f actor is not applicable. Some candidates
made a mistake with the unit conversion in the value of the time.

(v) This was a dif ficult question, with only the very strongest candidates demonstrating an ability to use
Lenz’s law correctly. The application of Lenz’s law lay in realising that the cause of the induced
e.m.f . is the rotation of the wheel. If current flows in the spokes, then it will cause a f orce on the
wheel in the opposite direction to the rotation. Applying the left-hand rule then leads to a deduction
that any current that flows will be from A to X. Finally, because current flows f rom low potential to
high potential inside an e.m.f. source (and high to low potential around any external circuit), end X
must be at the higher potential. A common misconception was that X is at the higher potential
because it cuts more f lux.

Question 2

(a) A significant minority of candidates did not give a definition of a quantity, but those that did answer
the question were mostly able to correctly define the vector quantity gravitational field as f orce per
unit mass (placed in the f ield).

(b) (i) There was some confusion among weaker candidates between the equations for gravitational force
between point masses and the scalar quantity gravitational field strength due to a point mass. The
more able candidates generally used the correct equation, but some did not appreciate that the
precision of the data provided in the question warranted a three signif icant f igure answer.

(ii) Most candidates were able to substitute the correct values into the equation f or gravitational
potential energy. Some candidates gave answers that did not reflect the precision of the data and
others f orgot that gravitational potential energy is always negative.

(c) (i) Many candidates were able to put together the equation for radiant flux intensity and the equation
f or gravitational field strength, and to eliminate x between them to arrive at the correct equation.
Candidates that used letters other than x f rom the question sometimes struggled with the
elimination if the distances they used in the two equations were not the same. Candidates should
be advised that it is always better to use the symbols def ined f or them in the question.

(ii) This question was well answered by many candidates. Of those that correctly read a pair of values
of g and L f rom the graph and substituted them together with the other relevant data into the given
equation, the common reasons for not going on to achieve full credit were either making a mistake

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with the powers of ten in those values from the graph, or forgetting that luminosity is a power and
giving the answer with an incorrect unit.

(iii) Many candidates answered correctly. Some struggled with the use of the Stef an–Boltzmann law,
with use of the permittivity of f ree space f or the Stef an–Boltzmann constant not unusual, and
various arithmetic errors such as forgetting to raise the temperature to the power 4 or f orgetting to
take the square root of r2 at the end. Some weaker candidates attempted to use the radiant f lux
intensity f ormula.

Question 3

(a) Full credit for this question was rare, indicating that the definition of specif ic latent heat is not well
known by candidates. Many definitions seen were dimensionally incorrect, defining specif ic latent
heat as an energy rather than as thermal energy per unit mass. The aspect that it is to do with
energy needed to change state at constant temperature was more successf ully articulated.

(b) (i) This question was generally well answered, with the majority of candidates achieving f ull credit.

(ii) Most candidates realised the need to apply the first law of thermodynamics, but were then unable
to arrive at the correct answer because they did not appreciate that the gas is doing work and so
the work done on the gas is negative.

(iii) Full credit by error carried f orward f rom the answer to (b)(ii) was common. Weaker candidates
f ound it difficult to work out the mass of the substance, with use of the volume of the gas with the
density of the liquid being the common incorrect starting point.

(c) Only the strongest candidates were able to give a response to this question that went beyond
IGCSE level physics. These stronger candidates were able to discuss the three terms involved in
the f irst law and how they dif f er between the processes of f usion and vaporisation.

Question 4

(a) Candidates who knew their ‘bookwork’ were generally able to correctly state three of the
assumptions of the kinetic theory. Weaker candidates of ten gave responses in terms of ‘gases’
rather than the molecules that make up the gas. A common misconception was that the
assumption dealing with the negligible volume of the molecules related to a single molecule rather
than to all of the molecules in the gas.

(b) Many candidates answered a different question from the one asked, and discussed why pressure
increases with temperature. Of the candidates that did address the question asked, most observed
that there are molecular collisions with the walls of the container, but only the strongest candidates
discussed the application of Newton’s laws to those collisions to explain the origin of the f orce on
the walls.

(c) Many candidates offered descriptions of the graphs rather than drew conclusions about the gases
and their samples. Responses that treated quantities that vary as if they were properties of the
samples were common. There were many different points that candidates could make by way of
conclusions about the gases and their samples, and stronger candidates f requently achieved f ull
credit.

Question 5

(a) A large number of candidates thought that the resultant force on the sphere was horizontal rather
than perpendicular to the string.

(b) (i) This question was generally well answered, with most candidates correctly deducing the amplitude
f rom the graph.

(ii) This question was also generally well answered. Some of the weaker candidates were conf used
between angular f requency and f requency.

(iii) Candidates that knew the syllabus equation for the energy of the oscillations were usually able to
use their values in (b)(i) and (b)(ii) to calculate the energy correctly.

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(c) This was a well answered question by candidates that understood this part of the syllabus, with
many achieving f ull credit.

Question 6

(a) Coulomb’s law was generally well known, and many candidates achieved f ull credit.

(b) Most candidates appreciated that the electric field is radially outwards, though care was needed
over the diagram to gain full credit. Radial lines are straight, so candidates should be advised to
use a ruler to draw them. The + symbols around the sphere were a usef ul guide to candidates to
help them to ensure that their f ield lines were evenly distributed.

(c) (i) Most candidates deduced the radius correctly f rom the graph.

(ii) Candidates generally knew the correct equation for the electric field strength due to a point charge,
but care was needed over the powers of ten when substituting a pair of values correctly read f rom
the curved part of the graph. Some candidates chose to use the value on the data page for 1 / 40
and substituted it into the denominator rather than the numerator; candidates that used the value of
the permittivity of f ree space generally substituted correctly.

(iii) Most candidates found it dif f icult to of f er a plausible explanation, with many cyclic arguments
presented such as ‘there are no field lines inside the sphere, so the electric field is zero ’. There was
a variety of ways in which candidates could approach the answer, and stronger candidates
generally were awarded credit.

Question 7

(a) Most candidates knew that, in general, capacitance is defined as charge per unit potential. Fewer
candidates were able to give the extra detail of how these quantities apply to the particular scenario
of the parallel-plate capacitor.

(b) (i) Many candidates achieved full credit for drawing a straight line from (0, 0) to (V, Q). Some did not
appreciate that charge is proportional to p.d. and drew a curved line.

(ii) This question was generally well answered, with many candidates knowing that the energy stored
in a capacitor is given by the area under the charge–p.d. graph, leading to W = ½QV.

(c) (i) This was a challenging question that required a good understanding of which quantities are
conserved during the process of connecting the capacitors. The mark scheme was structured in
such a way that candidates could gain partial credit for getting diff erent aspects of the task right.

It was notable that many candidates gave responses that they must have known could not be
correct, because they were dimensionally incorrect. The p.d.s had to have been in terms of V, and
the charges had to be in terms of Q, and it is reasonable to expect A Level candidates to realise
that answers that were not in terms of V and Q, respectively, could not possibly be correct. Many of
the strongest candidates did give a completely correct response.

(ii) Some candidates went to the trouble of actually calculating the energies, but this was not
necessary. Candidates were expected to realise that the only possible answer is that the f inal
energy stored must less than the original energy stored, because some energy is dissipated during
the charge redistribution.

Question 8

(a) Candidates found it difficult to def ine f requency correctly. Common incorrect answers included
discussing the number of ‘waves’ rather than the number of cycles/oscillations, attempting to define
a quantity in terms of units, and def ining f requency as the reciprocal of period.

(b) (i) This question was generally well answered.

(ii) This was also a well answered question, with many candidates achieving f ull credit.

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(iii) This question was generally well answered.

(c) This was a more demanding question. The aim of the question was to show separately the
calculation of the mean and peak powers, from the r.m.s. and peak currents respectively, and then
to use them to prove that the mean power is half the peak power. It was common f or weaker
candidates to take the relationship to be proved as the starting point, and to calculate one of the
powers using it. This was not what they were asked to do and could not achieve f ull credit.

Question 9

(a) Many candidates needed to pay closer attention to the command word for this question. ‘Explain’
requires more than just a statement. Candidates needed to do two things to gain credit; f irstly, to
establish that diffraction and interference are characteristic behaviour associated only with waves,
and secondly, to conclude from that that the observation provides evidence for the wave nature of
moving electrons. Many candidates did the second of these but not the first. Some candidates gave
contradictory responses by suggesting that the observation provides evidence f or both the wave
nature and the particle nature of electrons.

(b) Most candidates were able to obtain credit f or the equation p = mv. Fewer candidates gave the
correct conservation of energy equation qV = ½mv 2. The strongest candidates correctly completed
the algebra by eliminating v between the two equations to arrive at the correct f inal answer.

(c) Many candidates realised that the increased momentum of the electrons decreases their de Broglie
wavelength, though some found it difficult to make the link. The strongest candidates were able to
articulate that the ef f ect of this change on the interf erence pattern is that the f ringe spacing
decreases.

(d) Both parts of this question were generally well answered, with many candidates achieving f ull
credit.

Question 10

(a) The meaning of ‘spontaneous’ was generally better understood than the meaning of ‘random’.
Many responses to the latter were too vague to be awarded credit, with weaker candidates
appearing to think that all aspects of radioactive decay are unpredictable. Candidates are expected
to realise that the unpredictability is only on the level of individual nuclei, and that on the
macroscopic scale the process is highly predictable. Understanding of the experimental evidence
f or the random nature of decay was generally not well articulated.

(b) (i) To give a creditworthy account of the dif f erences between nuclear f ission and nuclear f usion,
candidates needed to be very clear when they were ref erring to a single nucleus and when they
were ref erring to multiple nuclei. Only a minority of candidates ex plained that f ission involves a
single nucleus splitting into multiple nuclei, with many describing processes that are more akin to
radioactive decay. Explanations of fusion often relied on the word ‘fuse’, which is part of the term
that the question is asking about, and so candidates needed to make clear that this involves two
nuclei joining together to make a single nucleus.

(ii) Many responses were seen that were not incorrect in what they said, but that did not answer the
question asked. There were many discussions, f or example, of mass def ect, but the question
asked for a discussion of the variation of binding energy per nucleon with nucleon number. A space
was provided for candidates to draw a sketch graph of this variation, and candidates that did this
(provided the graph was correctly labelled) were generally more successf ul in answering the
question than those that did not.

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PHYSICS

Paper 9702/43
A Level Structured Questions 43

Key messages

• It is important that candidates use technical language accurately. Examples of words that are of ten
conf used by candidates are atom and molecule, nuclide and nucleus, and force and f ield. Candidates
are not able to obtain full credit if they use an inappropriate word that makes the response technically
incorrect.

• In def ining quantities, candidates need to take care to ensure that the def inition they give is
dimensionally correct. This often requires use of the phrase ‘per unit’ where the quantity being def ined
is the ratio between two other quantities, or ‘product’ where the quantity being def ined is two other
quantities being multiplied together. Examiners will only consider symbol equations to be part of a
def inition if the symbols used are identif ied.

• Candidates need to take care to ensure that they read the question properly, understand what is being
asked and give responses that answer the question that is asked. It is not uncommon to f ind
candidates giving answers to questions that were not asked, but that have been asked in recent past
papers. Candidates should be advised not to rely heavily on memorising previous mark schemes.

• When answering questions involving calculations, it is important for candidates to show their reasoning
clearly. This includes taking care to use the correct conventional symbols f or physical quantities. If
working is clear and based on use of correct physics, it is often possible for examiners to award partial
credit even when the final answer is incorrect. Incorrect answers that are not supported by working
cannot be awarded credit.

• Answers to numerical questions should be given to an appropriate number of signif icant f igures; the
precision of the data provided in the question is generally indicative of the appropriate number of
signif icant f igures f or an answer. When perf orming intermediate calculations within a question,
candidates should take care to avoid premature rounding; as a general rule, any intermediate calculated
values should always carry at least one more signif icant f igure than will be used in the f inal answer.
Candidates should be made aware that giving answers to an inappropriate number of significant figures,
or that are inaccurate as a result of rounding intermediate values prematurely, can both lead to f ull
credit not being awarded.

General comments

The question paper contained questions of a variety of levels of diff iculty, enabling candidates at dif f erent
levels of ability to show what they know. Candidates who knew the ‘bookwork’, read the questions caref ully,
took care over their use of technical language and answered the questions asked were able to perform well.

Questions asking f or an explanation or reason were of ten answered in a way that just described the
inf ormation that was given in the question, diagram or graph. Candidates should be advised not to do this,
as it wastes time and uses up answer space, and cannot lead to any credit being awarded.

Several questions required drawing of lines, including sinusoidal waves, curves and straight lines. Many
candidates would have achieved more credit by the appropriate use of a pencil, ruler and eraser, thereby
allowing them to easily and clearly correct or clarif y their work. Statements written next to diagrams
describing how the drawing should look do not compensate f or inaccurate drawing.

There was no evidence that candidates had insuf f icient time in which to complete the paper.

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Comments on specific questions

Question 1

(a) Most candidates understood that stating Newton’s law of gravitation involved two separate
proportionalities. The most common errors occurred with regard to the separation of the masses,
either through the use of the non-specific term ‘distance’, or by not identif ying that the separation
term was a squared one.

(b) (i) Stronger candidates identif ied that it was the gravitational f orce that caused centripetal
acceleration, and that the f orce acted perpendicular to the direction of satellite motion (or its
velocity). Weaker candidates implied that centripetal f orce was a separate f orce to that of
gravitation.

(ii) Candidates were expected to start with Newton’s gravitational equation and relate that f orce to
circular motion. Most candidates appreciated that this was a ‘show that’ question, and so they laid
out their derivation and substitutions clearly. Stronger candidates explained in words what the two
constants A and B represented.

(iii) This was a question in which the ability to set working out clearly was of signif icant benef it to the
candidate, as credit was available f or stages in the process of getting to the f inal answer. In
comparison to (ii) above, many candidates were not able to explain their series of calculations and
expressions. Stronger candidates realised that the quantities on the axes of the graph did not
immediately match the expression given in (ii). Theref ore, some reorganisation was required
bef ore the gradient given in the straight-line equation y = mx + c could be equated with the
calculated value of the gradient taken from two points on the graph. Most candidates realised that
taking well separated points yielded a more precise value for the gradient, although it was common
to see the power of ten f or height h being overlooked in this calculation.

Question 2

(a) Most candidates understood the need to provide a ratio with regard to thermal energy and mass
(f or example, by using the word ‘per’). Fewer candidates repeated the process for the temperature
change. Instead, there were of ten incorrect inclusions of specif ic units of temperature, or
ref erences to a single unit of temperature change.

(b) (i) This question was generally well answered. When weaknesses were shown, they related to
thermal equilibrium and thermal isolation, where the blocks needed to be identif ied as being the
system considered.

(ii) Some candidates were not able to appreciate that the change in temperature f or the two blocks
was not equal, and that those dif f erent temperature changes needed to be included in the
calculation.

Question 3

(a) (i) This question was generally well answered, the mixing up of the terms ‘number’ and ‘amount’ with
ref erence to particles being the only signif icant area of conf usion. Where a meaning f or the
Avogadro constant was given in terms of carbon-12, it was essential for candidates to appreciate
that it was specif ically the number of atoms being considered.

(ii) The majority of the candidates equated the three constants correctly.

(b) (i) In this question, stronger candidates appreciated that the terms in the question needed to be
included in their expressions rather than numerical values or other terms.

(ii) Most candidates appreciated that the line needed to pass through the origin. Stronger candidates
drew a curve with a positive, decreasing gradient that did not have a peak.

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Question 4

(a) The proportionality between acceleration and displacement was well understood, but the opposite
direction of the two quantities was less clearly explained by some candidates. This question
provided an example where quoted equations gained no credit without an explanation of each term
used.

(b) (i) The use of a velocity–height graph did not appear to be problematic for most candidates in either
(i) or (ii).

(ii) As a ‘show that’ question, candidates were expected to indicate a pathway from values to the f inal
answer. Where the starting equation of  = v0 / x 0 was used, candidates did not always distinguish
the maximum values f or v and x using subscripts.

(iii) The majority of the candidates correctly used the given values of angular f requency to calculate the
period to two significant figures, as required. Weaker candidates of ten gave their answer to only
one signif icant f igure.

(iv) Candidates found it difficult to sketch the sinusoidal curve without error, although some tolerance
was given for f reehand drawing. Stronger candidates marked intermediate points on their graph to
aid their drawing of the curves. Many candidates were not able to identif y that the curve should
start at t = 0 with h at its lowest value. Apart from this, the most common errors involved a start and
f inish to the curve at t = 0 s and t = 6 s that was too sharp, and lines that were wrongly or
insuf ficiently curved between the peaks and troughs. The ability to draw a correct sinusoidal shape
is one that would have been applied to good effect in this question. Credit was gained where care
was taken with the position and height of the peaks and troughs.

Question 5

(a) Stronger candidates were aware of both the proportionality between electric f ield and electric
potential gradient, and the negative relationship between them. Identif ying the f irst part of the
relationship was a prerequisite f or achieving credit f or the second part. Weaker candidates
described the f ield and potential as being proportional to each other.

(b) Two approaches were possible for this question. Most candidates considered the two scenarios
with either like or unlike charges, and explained how that would affect the electric field and electric
potential. There was also the possibility of considering the constituent contributions from X and Y to
the resultant of the two quantities, one a scalar and one a vector. Weaker candidates discussed
only one field and ref erred to the situation at inf inity as a point where both quantities are zero,
rather than consider the situation given in the question. The f act that potential is a scalar quantity
and electric f ield a vector was not considered very of ten.

(c) (i) In this ‘show that’ question, the individual potential contributions of X and Y needed to be shown
and then equated to achieve the final relationship between distances y and x. Most candidates
achieved this, but in a small number of cases the working was compressed in such a way that the
required f ull working was not shown.

(ii) Most candidates were able to provide the correct expression.

(iii) Many candidates were able to derive a correct expression for the electric f ield strength due to Y.
Fewer candidates appreciated that, because X and Y were opposite charges, the electric f ields
would be in the same direction and theref ore their magnitudes needed to be added.

Question 6

(a) (i) Most candidates correctly indicated a conversion or change of the current or voltage to d.c.

(ii) Candidates found the task of describing the process of both types of rectification challenging. Many
chose to describe the mechanics of the conversion in terms of the number of diodes used, or the
dif ferent power outputs. Other candidates attempted to describe what happened to a sinusoidal
wave, in words or via unlabelled sketch graphs. Neither approach specif ically addressed the

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question. Better answers referred directly to what was happening to the voltage (or current) during
each half -cycle.

(b) (i) Sketches were generally drawn suf f iciently accurately to achieve f ull credit.

(ii) The use of the capacitor in this particular circuit was understood by most candidates.

(c) (i) This question was generally well answered. Where answers were given in f arads rather than
microfarads, there was a requirement that the correct units were also shown to achieve f ull credit.

(ii) Many candidates were able to f ollow through the substitution of values into the exponential
equation to calculate a correct final answer. Weaker candidates did not realise that the time period
to be taken was a maximum of 0.01 s. Some candidates took points for a small portion of the decay
period (i.e. less than 0.01 s). Whilst this was a perf ectly valid approach mathematically, a small
time period made it more likely that inaccuracy in reading the value would occur. Candidates
should therefore be encouraged to take as large a time period as they can for such measurements.

Question 7

(a) As with Question 2(a), candidates needed to clearly identify the two ratios in their def inition. They
needed to make clear that they were ref erring to the length of wire (or the current) being
perpendicular to the f ield, rather than discussing the direction of the f orce.

(b) Many candidates could not be awarded credit for their sketch drawing because of poor accuracy.
Avoidable errors included non-circular ‘circles’, signif icant gaps between the start and f inish of
circles and missing direction arrows. Candidates who made their first circle small were more likely
to be able to clearly show an increase in spacing with distance f rom the wire.

(c) (i) The key to achieving full credit in this question was to consistently identify that the interaction was
between the current in one wire and the magnetic field due to the other wire. Weaker candidates
talked imprecisely about f ields and currents, or simply ref erenced Newton’s third law without
explanation.

(ii) Af ter the more difficult part of identifying the direction of force F, a significant number of candidates
drew a line of action whose direction missed wire Y.

(iii) Stronger candidates clearly compared magnitudes and directions of the forces, using those words
in many cases. Weaker candidates referred to f orces being ‘the same’, which was insuf f iciently
precise.

(iv) Many answers needed to be given with more precision to gain full credit. As in (c)(i), explaining that
the current in one wire (X) and the f ield in the other wire (Y) had both changed direction avoided
any ambiguity.

Question 8

(a) Most candidates identif ied the name of the ef f ect in question.

(b) (i) This question was generally well answered, with candidates knowing how to calculate the work
f unction value.

(ii) Some candidates who achieved full credit in (b)(i) did not appreciate that the work function energy
needed to be included in the energy equation.

(c) This question tested candidates’ understanding of the earlier parts of (b). A correct use of the
scales on the graph was also required. Most candidates correctly identif ied both the threshold
f requency and drew the correct line f or f requencies above that.

Question 9

(a) (i) Most candidates were able to correctly recall the particle name.

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(ii) As a ‘show that’ question, both working and answer were required, although a unit was not required
as it was given in the stem of the question. Weaker candidates of ten did not clearly show the
conversion of the half -lif e to seconds.

(iii) Most candidates correctly gave the equation linking activity and the number of undecayed nuclei.
However, it was common to see candidates mixing up the two methods of calculating that number
of undecayed nuclei. Weaker candidates often gave a wrong power of ten in their answer because
they were not able to correctly assess whether the mass should be in grams or kilograms,
depending on the method used.

(b) (i) A broad range of responses were produced in this question. Some candidates gave good answers
and made more than the required number of creditworthy points for full credit. Identification of pair
annihilation was the marking point most commonly seen. Weaker candidates ref erred to either
mass being converted to energy, or to the production of gamma rays in a general sense. Stronger
candidates identified the total conversion of the pair mass and described the production of a pair of
gamma photons for each annihilation, going on to describe what happened to those two photons
af ter production. One aspect that candidates could benefit f rom having reinf orced is that it is the
dif f erence in photon arrival times at the detector that is used to identif y the tracer position.

(ii) Candidates who took a consistent approach in their explanation avoided the pitfall of contradicting
themselves. Stronger candidates focused f irstly on the importance of a long enough half -lif e to
allow there to be sufficient activity at the point the sample was inside the body. They then identified
that too long a half-life meant that the patient was exposed to harmf ul radiation unnecessarily.
Weaker candidates either regarded the half-life of 110 minutes as being a time during which the
procedure had to be completed, or discussed that time period as being without risk to the patient.

Question 10

(a) Some candidates would have benefited from re-reading their answer to this question before moving
on. Of ten answers gave a general picture of the topic without focusing on what this question was
actually asking. It was common to see answers that did not mention redshif t at all, which reduced
the credit available. Weaker candidates were not able to move on from writing about an observer
on Earth, whilst stronger candidates discussed the implication of those observations f or the more
general movement of galaxies in relation to each other.

(b) (i) Many candidates were familiar with the method, starting with a correct equation to link luminosity,
radiant f lux intensity and distance, to then calculate the value of the distance of the galaxy from the
Earth. All data was provided to three significant figures, so answers also needed to be given in that
way. Most candidates successf ully noted this.

(ii) As in (b)(i), the majority of the candidates successfully answered this question. The most common
error was to use the wrong wavelength as the denominator.

(c) (i) This question was also well answered. It was not necessary for the line drawn to physically pass
through the origin for full credit to be obtained, as long as the extrapolation was clear and the line
was straight.

(ii) Whilst minor spelling errors in Hubble’s name were condoned, candidates who described the
quantity as a law did not gain credit.

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PHYSICS

Paper 9702/51
Planning, Analysis and Evaluation 51

There were too f ew candidates f or a meaningf ul report to be produced.

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PHYSICS

Paper 9702/52
Planning, Analysis and Evaluation 52

Key messages

• In Question 1, candidates’ responses should include detailed explanations of experimental procedures

such as how to control variables, how to take measurements and how to analyse the data.

• The numerical answers towards the end of Question 2 require candidates to show all their working and
f or the values to be correctly evaluated with appropriate units. A full understanding of significant f igures
and the treatment of uncertainties is required.

• Candidates need to understand how to use logarithms (both logarithms to base ten and natural
logarithms) correctly, including calculating their uncertainties.

• The practical skills required f or this paper should be developed and practised with a ‘hands -on’
approach throughout the course.

General comments

In Question 1, it is advisable that candidates should think caref ully about how they would perf orm the
experiment in the laboratory using the bullet points given to aid their answer. Planning a f ew key points
bef ore answering Question 1 is usef ul. Some weaker candidates were unsure of the independent and
dependent variables in the experiment, while other candidates gave a vague quantity of ‘temperature’, which
could not gain credit. Many candidates were successful in the analysis section, with clear identif ication of
how the constant could be determined. Weaker candidates often suggested a suitable graph, but were not
explicit in how the relationship could be proved or how to determine the constants K and Z. To be awarded
credit for additional detail, candidates should take care to describe exactly how each measurement will be
obtained, including both the equipment used and the method to take the measurement. It is essential f or
candidates to have experienced practical work in preparation f or answering this question.

In Question 2, candidates should be f amiliar with completing a results table f or quantities and their
uncertainties, and with finding the gradient and y-intercept of a graph. For some candidates, credit was not
awarded because the plotted points were not balanced about the line best fit , the worst acceptable line did
not pass through the error bars correctly or coordinates were wrongly read off when determining the gradient
and/or y-intercept. Another source of dif f iculty was determining the percentage uncertainty in n.

In question parts requiring mathematical manipulation, stronger candidates clearly stated the equation used
with correct substitution of numbers, and then calculated the answer and included an appropriate unit.
Candidates should be encouraged to set out their working logically so that it can be understood.

Comments on specific questions

Question 1

Most candidates correctly identif ied the independent and dependent variables. A signif icant number of
candidates did not gain credit because they stated that the dependent variable was temperature as opposed
to change in temperature or . Some candidates also incorrectly stated that  was the independent
variable and L was the dependent variable. Candidates should then consider the control of variables and to
explicitly state the quantities that need to be kept constant to make the experiment a f air test. In this
experiment, it was expected that candidates would state that t would be kept constant. There was additional

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credit for also stating that A, m and V would be kept constant. Credit is not given for simply stating ‘control’ t
since this is just repeating the stem of the question and does not indicate what is meant by ‘control’.

Candidates were awarded credit for a clearly labelled diagram. Diagrams should be drawn of the workable
experiment. In this experiment, it was expected that candidates would show that the coil of wire was totally
submerged in the oil with a thermometer placed in the oil to measure the temperature. Some weaker
candidates incorrectly suggested the use of water baths or Bunsen burners , which could not be given credit.

Candidates needed to explain how the potential difference V was determined. Stronger candidates drew a
circuit diagram showing a power supply connected to the wire with a voltmeter in parallel with the wire. A
common mistake was to place the voltmeter in series with the power supply and wire. Another error was to
place a variable resistor in the circuit and then measure the potential difference across the variable resistor
and the wire.

Credit was given f or describing how  was determined by measuring the initial temperature of the oil,
measuring the final temperature of the oil and then f inding the dif f erence between the two temperatures.
Additional credit was awarded to candidates who suggested stirring the oil to ensure that the oil was at a
unif orm temperature or f or keeping the initial temperature of the oil constant.

Candidates also gained credit for stating the measuring instruments to measure t and L. Apparatus drawn on
its own with no indication of how it will be used, e.g. a drawing of a stopwatch, cannot gain credit. A common
error by some candidates was to measure the length of the coil as opposed to the length of the wire. Some
candidates gained additional credit for suggesting that the coil should be unwound to measure L. A small
number of candidates also gained credit f or a description of how the circumf erence of the coil could be
measured and the length calculated by multiplying by the number of turns.

Candidates also needed to state suitable methods to collect values of A and m. Of ten a micrometer or
calipers were suggested to measure the diameter of the wire and then an appropriate equation was given to
determine A which included the diameter. Some weaker candidates did not gain credit because they stated
‘use a micrometer to determine A’ or ‘use a micrometer to measure the radius of the wire’. The physical
measurement would be the diameter of the wire. There was additional credit f or stating that the
measurements of the diameter of the wire would be repeated at dif f erent positions along the wire and a
mean value of diameter would be calculated. A statement of ‘repeat measurements of diameter’ on its own
was not considered sufficient. Many candidates suggested a balance to measure m but did not then describe
the method of measuring the mass of an empty container, adding oil to the container, measuring the mass of
the container and oil and finding the difference. Candidates should be advised not to write ‘a scale’ (which
can have several meanings) if they intend to ref er to a balance.

Many candidates suggested correct axes for a graph. Candidates must explicitly state the quantities to be
plotted on each axis either in the text or on drawn axes – credit is not given for just writing y = mx + c under
an expression.

Candidates also needed to explain how the graph would conf irm the suggested relationship. Candidates
need to use the words ‘relationship is valid if’ and the word ‘straight’ to describe the line. For this experiment,
credit was not given for stating that the straight line would pass through the origin (since there would be a y-
intercept). Stronger candidates of ten gave an expression f or the y-intercept.

Candidates needed to explain how they would determine a value f or the constants K and Z f rom the
experimental results using the gradient and y-intercept. To gain credit, the constants K and Z had to be the
subject of the relevant equations. Credit was not awarded to candidates who did not correctly identif y
appropriate axes f or a graph to plot.

The additional detail section had a maximum of six marks that could be awarded. Candidates should be
encouraged to write their plans including appropriate detail; some candidates’ answers suggested that they
did not have suf f icient practical experience. Vague responses were not credited. It is essential that
candidates’ answers are relevant to the planned experiment rather than general ‘textbook’ rules f or working
in the laboratory.

When describing saf ety precautions, candidates should be encouraged to explain how the precaution
proposed is relevant to the experiment. In this experiment, precautions could be taken that were relevant to
the potentially hot oil, hot beaker or hot wire, or the potential spillage of the oil. As a precaution against
spillage, it was expected that candidates would suggest placing the experiment in a tray or container.

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Question 2

(a) Candidates who were mathematically confident were able to work through the algebra and achieve
credit. Candidates should use the white space on the question paper to rearrange the equation into
an equation of a straight line.

(b) The majority of the candidates calculated d2 correctly. Many candidates also correctly calculated
the uncertainty in d2. A significant minority of candidates incorrectly calculated the uncertainty as
0.4, multiplying the absolute uncertainty in d by 2 (i.e. 2 × 0.2).

(c) (i) The data points were straightforward to plot. It is expected that the data points plotted should be
clearly represented. The plotting needed to be within half a small square. This meant that plotting
(3.28, 458) on the gridline (3.25, 455), for example, was incorrect since it is more than half a small
square out in both the x-direction and the y-direction. When plotting points, the diameter of each
point should be less than half a small square. Candidates need to take greater care over the
accuracy of the error bars and ensure that the error bars are symmetrical about their plotted data
point.

(ii) Most candidates appear to be using a sharp pencil and a transparent 30 cm ruler. For correctly
plotted data, the line of best fit did not pass through both the highest and lowest points. The worst
acceptable line was drawn well in general, and many stronger candidates drew a line that passed
through all error bars.

Candidates should clearly label the lines drawn as required by the question. Clear labelling should
also assist candidates when they determine the gradient and y-intercept. Where a dashed line
represents the worst acceptable line, the dashed parts of the line should cross each of the error
bars.

(iii) Most candidates clearly demonstrated the points that they used to calculate the gradient. Some
candidates misread coordinates or did not use a triangle that covered more than half of the drawn
line. A small number of candidates chose data points that did not lie on the lines, of ten using data
f rom the table that is close to the line instead. Candidates should be encouraged to select two
points on the line of best f it which are easy to read, i.e. points that are on grid lines.

When determining the uncertainty in the gradient, candidates need to show their working, including
the coordinates that they have used f rom the worst acceptable line and how the uncertainty is
determined f rom the gradients of the line of best f it and the worst acceptable line.

(iv) The majority of the candidates who were awarded full credit set out their working clearly. Stronger
candidates often substituted data f rom the gradient calculation in (c)(iii) into y = mx + c. Some
weaker candidates incorrectly read of f the y-intercept where the x-axis reading was 1.0. Other
errors seen included incorrectly dividing the y value by mx, inconsistent use of powers of ten
between the gradient and the y-axis value used, or calculating mx – y to give a positive value.

When determining the uncertainty in the y-intercept, candidates needed to show their working
including both the gradient and a data point f rom the worst acceptable line. In calculating the
absolute uncertainty, there must be evidence of subtraction between the y-intercept of the line of
best f it and the y-intercept of the worst acceptable line. Many candidates incorrectly attempted to
determine the uncertainty in the y-intercept by either assuming that the fractional uncertainty in the
gradient was the same as the f ractional uncertainty in the y-intercept or by adding f ractional
uncertainties.

(d) (i) Credit was not gained for substituting data values from the table. Most candidates realised that the
constant B was equal to –y-intercept. Some candidates did not gain credit since they did not give
their values of B and n to an appropriate number of signif icant f igures, of ten giving n to one
significant figure (too few) or sometimes writing five significant figures (too many). Most candidates
were able to calculate a value f or n using the gradient and either the y-intercept or B. Some
candidates who were confused about the negative y-intercept corrected their error at this stage but
did not then return to (c)(iv) to correct the original error. The common error in this question was the
determination of units. Most candidates realised that B had the unit cm2, but many candidates did
not understand that n did not have a unit.

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(ii) To gain credit, candidates needed to show their method. Many candidates realised that the
percentage uncertainty in the gradient needed to be added to the percentage uncertainty in the y-
intercept. Only the stronger candidates correctly multiplied their answer by 0.5 to allow f or the
square root in determining n. Some candidates used a maximum or a minimum method – clear
working showing how each of the maximum or minimum values was obtained was needed f or
credit. Where B was used, a clear method needed to be shown as to how the maximum or
minimum value of B was calculated.

(e) It was essential that candidates showed their method of working. Stronger candidates wrote down
the equation and clearly substituted in their values. Some weaker candidates were challenged by
the negative sign from the y-intercept. Weaker candidates often found the f inal determination of 
f rom sin2  challenging.

© 2024
 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

PHYSICS

Paper 9702/53
Planning, Analysis and Evaluation 53

Key messages

• In Question 1, candidates’ responses should include detailed explanations of experimental procedures

such as how to control variables, how to take measurements and how to analyse the data.

• The numerical answers towards the end of Question 2 require candidates to show all their working and
f or the values to be correctly evaluated with appropriate units. A full understanding of significant f igures
and the treatment of uncertainties is required.

• Candidates need to understand how to use logarithms (both logarithms to base ten and natural
logarithms) correctly, including calculating their uncertainties.

• The practical skills required f or this paper should be developed and practised with a ‘hands -on’
approach throughout the course.

General comments

In Question 1, it is advisable that candidates should think caref ully about how they would perf orm the
experiment in the laboratory using the bullet points given to aid their answer. Planning a f ew key points
bef ore answering Question 1 is useful. Many candidates were successful in the analysis section, with clear
identification of how the constants could be determined. Weaker candidates of ten suggested a suitable
graph, but were not explicit in how the relationship could be proved or how to determine the constants K and
Q. To be awarded credit for additional detail, candidates should take care to describe exactly how each
measurement will be obtained, including both the equipment used and the method to take the measurement.
It is essential for candidates to have experienced practical work in preparation f or answering this question.

In Question 2, candidates should be f amiliar with completing a results table f or quantities and their
uncertainties, and with finding the gradient and y-intercept of a graph. For some candidates, credit was not
awarded because the plotted points were not balanced about the line of best fit , the worst acceptable line did
not pass through the error bars correctly or coordinates were wrongly read off when determining the gradient
and/or y-intercept. Candidates f ound it dif f icult to determine the absolute uncertainty in E.

In question parts requiring mathematical manipulation, stronger candidates clearly stated the equation used
with correct substitution of numbers, and then calculated the answer and included an appropriate unit.
Candidates should be encouraged to set out their working logically so that it can be understood.

Comments on specific questions

Question 1

Most candidates correctly identif ied the independent and dependent variables. Candidates should then
consider the control of variables and to explicitly state the quantities that need to be kept constant to make
the experiment a fair test. In this experiment, it was expected that candidates would state that D would be
kept constant. There was additional credit for also stating that A, B, L and m would be kept constant. Credit
was not given for stating ‘control’ D since this is just repeating the stem of the question and does not indicate
what is meant by ‘control’.

Candidates were awarded credit for a clearly labelled diagram. Diagrams should be drawn of the workable
experiment. In this experiment, it was expected that candidates would show point P, labelled on a bench,

© 2024
 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

with a light gate positioned at P connected to a data logger. Ideally the trolley is drawn with an interrupt card
attached so that the speed of the trolley can be measured by the light gate at point P. Some candidates also
were given credit here f or showing how the block would be held stationary, for example by using a G-clamp.
Stronger candidates also thought about the use of a reference marker f or the accurate measurement of s or
D and indicated this on the diagram.

Candidates needed to explain how the velocity v was determined at point P. A common error was to describe
the determination of the average velocity over distance D. Candidates should be encouraged to avoid this
mistake by carefully reading the question and noting down the meaning of each variable bef ore starting
Question 1. Many candidates did not gain credit since their descriptions did not contain detail of how v is
determined. Stronger candidates described an interrupt card (with a measured length) passing through the
light gate at P and then stated that v = length of card / time measured on data logger.

Candidates also gained credit for suggesting measuring s, L and D with the correct instruments. Apparatus
drawn on its own with no indication of how it will be used, e.g. a drawing of calipers, does not gain credit.
Candidates should caref ully consider which measuring instrument is suitable f or the measurement of a
length. A micrometer should only be suggested if the measurement is likely to be very small ; a micrometer
was not appropriate to determine s in this experiment.

Candidates also needed to state suitable methods to collect values of A and m. Some candidates incorrectly
assumed that the magnet was cuboid, although the question stated that it was a cylinder. Often a micrometer
or calipers were suggested to determine the diameter of the cylindrical magnet and then an appropriate
equation was given to determine A, including the diameter. Some weaker candidates did not gain credit
because they stated ‘use a micrometer to determine A’ or ‘use a micrometer to measure the radius of the
magnet’. Credit was also not given if the diameter was measured with just A = πr2 given, since a description
of how r is obtained is also required if using that equation for A. The physical measurement to determine the
radius and/or area is the diameter. Most candidates suggested a balance to measure m.

Many candidates stated the use of a Hall probe but did not give the method of measuring B. Some
suggested that the probe should be at right angles but did not state how this could be checked. There were
some excellent methods described, discussing the rotation of the probe so that a maximum reading was
obtained or repeating the measurement by reversing the probe and measuring in it in the opposite direction
and determining the mean.

Many candidates suggested correct axes for a graph. Candidates must explicitly state the quantities to be
plotted on each axis either in the text or on drawn axes – credit is not given for just writing y = mx + c under
an expression.

Candidates also needed to explain how the graph would conf irm the suggested relationship. Candidates
need to use the words ‘relationship is valid if’ and the word ‘straight’ to describe the line. In this experiment,
credit was not given for stating that the straight line would pass through the origin (since there would be a y-
intercept). Stronger candidates of ten gave an expression f or the y-intercept.

Candidates needed to explain how they would determine a value f or the constants K and Q f rom the
experimental results using the gradient and y-intercept. To gain credit, the constants K and Q had to be the
subject of the relevant equations. Credit was not awarded to candidates who did not correctly identif y
appropriate axes f or a graph to plot.

The additional detail section had a maximum of six marks that could be awarded. Candidates should be
encouraged to write their plans including appropriate detail; some candidates’ answers suggested that they
did not have suf f icient practical experience. Vague responses were not credited. It is essential that
candidates’ answers are relevant to the planned experiment rather than general ‘textbook’ rules f or working
in the laboratory.

When describing saf ety precautions, candidates should be encouraged to explain how the precaution
proposed is relevant to the experiment. In this experiment, precautions could be taken to stop the trolley
rolling off the bench. Suggestions that were credited included a barrier at the end of the bench or a cushion
positioned after point P on the diagram. The suggestion of sand trays on the f loor did not gain credit since
this was a solution to the trolley falling; it would be better to take precautions to prevent this in the first place.

© 2024
 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

Question 2

(a) Candidates who were mathematically confident were able to work through the algebra and achieve
credit. Candidates should use the white space on the question paper to rearrange the equation into
an equation of a straight line.

(b) The majority of the candidates calculated 1 / I correctly. Many candidates also correctly calculated
the uncertainty in 1 / I. A minority of candidates incorrectly gave one or more of the 1 / I values to
more than 4 or less than 3 signif icant f igures.

(c) (i) The data points were straightforward to plot. It is expected that the data points plotted should be
clearly represented. The plotting needed to be within half a small square. This meant that, f or
example, plotting (2.22, 6250) on the horizontal gridline (2.22, 6260) was incorrect since it is more
than half a small square out in the y-direction. When plotting points, the diameter of each point
should be less than half a small square. Candidates need to take greater care over the accuracy of
the error bars and ensure that the error bars are symmetrical about their plotted data point.

(ii) Most candidates appear to be using a sharp pencil and a transparent 30 cm ruler. For correctly
plotted data, the line of best fit did not pass through both the highest and lowest points. The worst
acceptable line was drawn well in general, and many stronger candidates drew a line which passed
through all error bars.

Candidates should clearly label the lines drawn as required by the question. Clear labelling should
also assist candidates when they determine the gradient and y-intercept. Where a dashed line
represents the worst acceptable line, the dashed parts of the line should cross each of the error
bars.

(iii) Most candidates clearly demonstrated the points that they used to calculate the gradient. Some
candidates misread coordinates or did not use a triangle that covered more than half of the drawn
line. A small number of candidates chose data points that did not lie on the lines, of ten using data
f rom the table that is close to the line instead. Candidates should be encouraged to select two
points on the line of best f it which are easy to read, i.e. points that are on grid lines.

When determining the uncertainty in the gradient, candidates need to show their working, including
the coordinates that they have used f rom the worst acceptable line and how the uncertainty is
determined f rom the gradients of the line of best f it and the worst acceptable line.

(iv) The majority of the candidates who were awarded full credit set out their working clearly. Stronger
candidates often substituted data f rom the gradient calculation in (c)(iii) into y = mx + c. Some
weaker candidates incorrectly read of f the y-intercept when the x-axis reading was 1.4. Other
errors seen included incorrectly dividing the y value by mx and inconsistent use of powers of ten
between the gradient and the y-axis value used.

When determining the uncertainty in the y-intercept, candidates needed to show their working
including both the gradient and a data point f rom the worst acceptable line. In calculating the
absolute uncertainty, there must be evidence of subtraction between the y-intercept of the line of
best f it and the y-intercept of the worst acceptable line. Many candidates incorrectly attempted to
determine the uncertainty in the y-intercept by either assuming that the fractional uncertainty in the
gradient was the same as the f ractional uncertainty in the y-intercept or by adding f ractional
uncertainties.

(d) (i) Credit was not gained for substituting data values f rom the table. Most candidates were able to
calculate a value f or E using the gradient and Z using the y-intercept. A common error in this
question was a power-of-ten error from the gradient, which comes from the candidate not correctly
converting the k from the x-axis of the graph. Another common error was in the determination of
units. Candidates should be encouraged to re-read the beginning of Question 2 at this point to
help them check that their units are correct. The question stated that E represented e.m.f and Z
represented a resistance, theref ore the correct units are V and  respectively.

(ii) To gain credit in this part, candidates needed to show a clear method. The strongest candidates
gained credit here f or showing that the absolute uncertainty in E is equal to the absolute
uncertainty in the gradient plus the 1 / 3 of the absolute uncertainty in Es. Other strong candidates

© 2024
 Cambridge International Advanced Subsidiary and Advanced Level
9702 Physics November 2024
Principal Examiner Report f or Teachers

gained credit by calculating the maximum E or minimum E and calculating the dif f erence between
that and their E value to obtain the absolute uncertainty. For this method to be given credit, f ull
substitution of numbers is required including the use of the correct maximum o r minimum Es value
within the calculation.

(e) It was essential that candidates showed their method of working. Strong candidates wrote down
the equation and clearly substituted in their values. Candidates could gain credit here by error
carried f orward, and they should be encouraged to continue through to an answer even if they f eel
that a mistake has been made earlier in the question.

© 2024