Cambridge International AS & A Level

PHYSICS 9702/35
Paper 3 Advanced Practical Skills 1 October/November 2024
MARK SCHEME
Maximum Mark: 40

Published

This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the
examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the
details of the discussions that took place at an Examiners’ meeting before marking began, which would have
considered the acceptability of alternative answers.

Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for
Teachers.

Cambridge International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2024 series for most
Cambridge IGCSE, Cambridge International A and AS Level components, and some Cambridge O Level
components.

This document consists of 9 printed pages.

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9702/35 Cambridge International AS & A Level – Mark Scheme October/November 2024
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Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptions for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond
the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for
any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other
syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme
where necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded
by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) Final value of s is greater than a and (a + s) ⩽ 70.0 cm. 1

1(b) Six (or more) sets of readings of a (different values) and s with the correct trend (as a increases, s decreases) and without 5
help from supervisor scores 5 marks, five sets scores 4 marks, etc.

Range: smin ⩽ 10.0 cm. 1

Column headings: 1
Each column heading must contain a quantity and a unit where appropriate.
The presentation of quantity and unit must conform to accepted scientific convention e.g. 1/a / cm–1 and no unit for s / a.

Consistency: All raw values of a and s must be given to the nearest mm. 1

Significant figures: 1
All values of s / a must be given to the same number of s.f. as (or one more than) the least number of s.f. in raw a and s
values.

Calculation: Values of s / a are correct. 1

1(c)(i) Axes: 1
Axes must be labelled with the correct quantities.
Scales must be chosen so that the plotted points occupy at least half the graph grid in both the x and y directions.
Scale markings are no more than 2 cm (one large square) apart.
Sensible scales must be used, no awkward scales (e.g. 3:10 or fractions).

Plotting of points: 1
All observations in the table must be plotted on the grid.
Diameter of plotted points must be ⩽ half a small square.
Points must be plotted to an accuracy of half a small square in both x and y directions.

Quality: 1
Trend of points must be positive.
All points in the table must be plotted (at least 5) on the grid for this mark to be awarded.
It must be possible to draw a straight line that is within  0.2 m–1 (0.002 cm–1) on the 1 / a axis (normally x-axis) of all plotted
points.

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Question Answer Marks

1(c)(ii) Line of best fit: 1

‘Best fit’ is judged by the balance of all points on the grid (at least five points) about the candidate’s line.
There must be an even distribution of points either side of the line along the full length.
Lines must not be kinked or thicker than half a small square.

Some candidates may choose to identify an anomalous point. If they identify one point as anomalous (e.g. by circling or
labelling) then this point is to be disregarded when judging the line of best fit. There must be at least five points left after the
anomalous point is disregarded.

1(c)(iii) Gradient: 1
The hypotenuse of the triangle used should be greater than half the length of the drawn line.
Both read-offs must be accurate to half a small square in both the x and y directions.
Method of calculation must be correct (not Δx / Δy).
Gradient sign on answer line consistent with graph drawn.

y-intercept: 1
Intercept read directly from the graph, with read-off at 1 / a = 0, accurate to half a small square in y direction.
or
Correct read-off from a point on the line substituted into y = mx + c or an equivalent expression.
Read-off accurate to half a small square in both x and y directions.

1(d)(i) Value of P = candidate’s gradient value and value of Q = candidate’s y-intercept value. 1
The values must not be written as fractions, roots or given to one significant figure.

Correct unit for P: m or cm or mm 1

and
no unit for Q.

1(d)(ii) Correct calculation of R with correct unit, e.g. g. 1

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Question Answer Marks

2(a)(i) Final L value in the range 89.0–91.0 cm with unit and L to nearest mm. 1

Final d value in the range 8.00–12.00 mm with unit and all raw values to the nearest 0.01 mm or all to the nearest 1
0.001 mm.

2(a)(ii) Justification for significant figures in V linked to significant figures in L and d. 1

2(b)(i) S0 in the range 0.030–0.150 m. 1

2(b)(ii) Percentage uncertainty based on an absolute uncertainty in S0 in range 0.2 cm (0.002 m) to 0.6 cm (0.006 m). 1
Correct method of calculation to find percentage uncertainty e.g. (absolute uncertainty / value from 2(b)(i))  100.
If repeated readings have been taken, then the uncertainty can be half the range (but not zero) if the working is clearly
shown.

2(b)(iii) Correct calculation of k. 1

2(c) Final T in range 0.30 s ⩽ T ⩽ 0.70 s. 1

At least two measurements of nT where n ⩾ 5. 1

2(d) Second value of M and second value of T. 1

Second value of T > first value of T. 1

2(e) Two values of r calculated correctly. 1

The final r values must not be written as fractions or given to only to one significant figure

2(f) Calculation of percentage difference between candidate’s two  values. 1

Comparison of percentage difference with 15% leading to a consistent conclusion.

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Question Answer Marks

2(g)(i) A Two readings are not enough to draw a (valid) conclusion (not “not enough for accurate results”, “few readings”). 4

B Difficult to measure S0 or S1 with a reason e.g. ruler disturbs lower rod while measuring / parallax error / ruler moves
during measurement as hand-held.

C S0 and/or S1 vary along the length of the rods with reason e.g. springs are of different lengths / rods bend / rod(s) not
uniform.

D Difficult to measure time or T with reason e.g. difficult to judge / identify / tell / know the start or end of an oscillation.

E Difficulty with oscillation(s) with reason e.g. springs move on rod / other modes of oscillation are present / mass hanger
swings (or moves) on rod / mass (hanger) hits the stand.

1 mark for each point up to a maximum of 4.

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Question Answer Marks

2(g)(ii) A Take more readings and plot a graph or take more readings and compare  values (not “repeat readings” on its own). 4

B Clamp ruler / pointers on rule

or
use calipers
or
measure between middles of rods / measure diameter of rod and take account in measurement.

C Use springs of identical length (and spring constant)

or
adjust positions of springs so that the extensions of each spring are the same
or
move mass hanger to make rods parallel.

D Fiducial mark at the centre of the oscillation

or
video / record / film with timer in view or view frame by frame
or
motion / position sensor located under the lower rod / mass hanger

E Carve / use grooves in rod

or
method of attachment to rod e.g. tape / glue / use adhesive putty for the springs or string

1 mark for each point up to a maximum of 4.

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