G.C.E.

A/L Examination March - 2017

Conducted by field Work Centre, Thondaimanaru
In Collaboration with
FWC
Northern Provincial Department of Education
Grade:12(2018) Physics Three hours
Instructions:
 Answer all the questions.
 Wright your Index number in the space provided in the answer sheet.
 Choose correct or most approprite answer and mark your response on the answer sheet with a cross (x)
(g = 10 N kg-1)

Part I
01) Unit Volume of energy is equalent to,
(1) Work (2) Moment (3) Pressure (4) Power (5) Force

02) The “reaction” force does not cancel the “action” force because
(1) They act on same body.
(2) They are in different line of action.
(3) They do not act on same body.
(4) They are in the same line of action and the same direction.
(5) The reaction exists only after the action force is removed.
03) The following readings x, y and z have been taken using correctly selected instrument
x = 3.32cm y = 2.433cm z = 0.354cm
x y z
(1) Vernier caliper Spherometer micrometer screw gauge
(2) Travelling microscope Spherometer micrometer screw gauge
(3) micrometer screw gauge micrometer screw gauge Spherometer
(4) Vernier caliper micrometer screw gauge Spherometer
(5) Travelling microscope Spherometer micrometer screw gauge

04) A particle moves in a fixed circular path constant angular speed (ω). The Variation of the
magnitude of the particles acceleration f with ω is best represented by
f f f f f

0 ω 0 ω 0 ω 0 ω 0 ω
(1) (2) (3) (4) (5)

Grade - 12 (2018) - March - 2017 1 Physics

 05) A phenomena which can be observed only in transverse waves
(1) Refraction (2) Diffraction (3) interference
(4) Super position (5) polarization
06) An object starting from rest moves first 50m at constant acceleration, next 200m with
uniform velocity and finally comes to rest after travelling a further 30m with constant
deceleration. The total time taken for the journey is 30 seconds. The maximum velocity
attained by the object is
(1) 2.7𝑚𝑠 −1 (2) 6𝑚𝑠 −1 (3) 6.7𝑚𝑠 −1 (4) 8.7𝑚𝑠 −1 (5) 12𝑚𝑠 −1

07) The figure below shows a loudspeaker (L) emitting sound continuously at a frequency of
400Hz along a straight line in the positive x direction. The graph represents the
displacement of the air particles from their respective equilibrium positions along the x -
axis at one particular instant.
A B C D E
L 𝑥

Displacement
𝑥
A B C D E

The instantaneous pressure maximum point/points is / are

(1) A, C, E (2) B, D (3) A (4) C (5) E

08) A ball is thrown horizontally with a velocity v, from a top v

of the tower height h, and the ball hits the ground making
an angle θ with horizontal as shown in the figure. Which h
of the values v & h gives maximum value of the θ?
v 10 ms-1 10 ms-1 30 ms-1 30 ms-1 50 ms-1
θ
h 30 m 50 m 30 m 50 m 10 m
(1) (2) (3) (4) (5)

09) A thick layer of oil with density 800Kg/m3 is floating above

water that has density 1000kgm3. A solid cylinder is
floating so that 1/3 is in the water, 1/3 is in the oil as shown Oil
in the figure. Additional oil is added until the cylinder is
Water
floating only in oil. What fraction of the cylinder is in the
oil?
(1) 3/5 (2) 3/4 (3) 2/3 (4) 8/9 (5) 4/5

Grade - 12 (2018) - March - 2017 2 Physics

 10) A ladder is in equilibrium on a vertical plane which is perpendicular
to the wall as shown in the figure below. One end of the ladder is on ladder
the rough horizontal ground and the other end is resting against a
rough vertical wall. Weight of the ladder (w), reaction forces at
upper and lower end of the ladder are S and R respectively which
force triangle represents forces act on the ladder?

(1) (2) (3) (4) S (5) S

R
w R R
w w R
w w
S R
S S
11) A student holds thin strip of paper below his lower lip and blows air horizontally over it. If
the surface area of one side of the paper is A and the mass of the strip is m speed v, with
which the air should be blown in order to keep the strip horizontal is (consider the density
of air 𝜌)

2mg mg mg mg 3mg
(1) 𝑣 = (2) 𝑣 = (3) 𝑣 = (4) 𝑣 = (5) 𝑣 =
ρA ρA 2ρA 3ρA ρA

12) Three trolley are free to move on a frictionless horizontal track. Trolley A has a mass of
2m and an initial speed 2v to the right; Trolley B has a mass of and an initial speed of v to
the left; Trolley C has a mass of m and is originally at rest. All collisions are perfectly
elastic.
A B C
2m m m

2v v
The velocity of the center of mass of the system of the three trolleys after the last collision
is
2v 3v 3v 3v v
(1) (2) (3) (4) (5)
3 4 2 5 3

13) The graph shows the acceleration (a) of a body of 4Kg mass with the
-2
distance (x) travelled by it, the work done in travelling a distance 5m a(ms )
is 10
(1) 10J (2) 20J (3) 50J
(4) 100J (5) 200J
𝑥(m)
0 5

Grade - 12 (2018) - March - 2017 3 Physics

 14) A wave moving from to right in a medium is represented graphically by the figure below
The graph actually shows the displacement of

Displacement

0
Distance

(1) Particles along the medium at various instants.

(2) Particles along the medium at a particular instant.
(3) Any one particle along the medium at various instants.
(4) The particle at the source at the start of the wave motion.
(5) Any one particle along the medium during a complete cycle.
15) Uniform cross section area of the U tube is partially filled with water, the length of the
water column is L. Oil with a density 2/3 that of water is added to one side of the tube
until the total length of oil equal to the total length of water. At equilibrium the difference
in heights of the two liquids columns is equal to
2L L L 3L L
(1) (2) (3) (4) (5)
3 2 3 4 4

16) The figure shows sphere and hemispheres in contact with various supporting surfaces that
are not frictionless of those the following correspond to configurations of stable
equilibrium

(A) (B) (C)

(1) (B) Only (2) (C) Only (3) (A) And (C) Only
(4) (B) And (C) Only (5) All (A), (B) and (C)
17) When an object is made to perform simple harmonic motion,
(1) The period of oscillation of the object depends on the amplitude of the oscillations.
(2) The force acting on the objects is always directed away from the equilibrium position.
(3) The total mechanical energy of the object depends on the amplitude of the oscillation
(4) The potential energy of the object is always constant.
(5) The kinetic energy of the object is always constant.
18) What is the maximum value of the force F such that the block F
shown in the figure, does not move? The coefficient of friction θ = 450
m
between the block and the horizontal surface is 0.5.
(1) 20N (2) 10N (3) 12N (4) 15N (5) =18N2kg

Grade - 12 (2018) - March - 2017 4 Physics

 19) A long glass tube is vertically in water. A tuning fork is struck and held over the open end
of the tube. Strong resonances are observed at two successive lengths 0.50m and 0.84m
above the surface of water. If the velocity of sound in air is 340ms -1 then the frequency of
the tuning fork and end correction of the tube are respectively
(1) 128Hz and 0.5cm (2) 256Hz and 1cm (3) 500Hz and 0.5cm
(4) 384Hz and 1cm (5) 500Hz and 1cm
20) A sonometer wire having mass per unit length of 40.0gm-1 and tension of 36N is
simultaneously with a tuning fork of frequency 300Hz while varying its vibration length
from a small value. In this process at one stage the wire resonates with tuning fork when
number of loops and length of the sonometer wire respectively will be
(1) 1and 5cm (2) 1and 10cm (3) 1and 20cm (4) 2and 20cm (5) 2and 5cm

21) What is the minimum angular speed, should the earth spin in order for a 70Kg human not
to be able to walk along the equator on the ground? (consider radius of earth is 6.4x106m)
(1) 1.2x10-3rads-1 (2) 1.25x10-3rads-1 (3) 1.1x10-4rads-1
(4) 1.5x10-3rads-1 (5) 1.2x10-4rads-1
22) Two identical cylinderical vessels with their base at same
level, each contains a liquid of density ρ, the area of either
base is A. The height of the liquid in the vessels are h1 and h2,
h1
controlled by valve S as shown in the figure , If the valve S h2
S
opens the work done by gravity in the equalizing level will be 2
h 1 −h 2 h 1 −h 2 2 h 1 −h 2
(1) Aρg (2) Aρg (3) Aρg
2 2 4
h 1 −h 2 2 2
h1 − h2 2
(4) Aρg (5) Aρg
4 2

23) R radius of circular disc with mass m with initial velocity v and an
angular velocity ω comes into contact with the ground as shown in
the figure. Friction is not negligible, so both the velocity and
ω v
angular velocity of the disc changes. What is the critical velocity
(vc) when the disc comes to instantaneous rest (in terms of angular
velocity ωc and R)?
R 2
(1) vc = Rωc (2) vc = ωc (3) vc = Rωc
2 3
3
(4) vc = Rωc (5) vc = 2Rωc
2

Grade - 12 (2018) - March - 2017 5 Physics

 24) The figure shows the resultant wave produced by two sound waves of slightly different
frequencies. the beat frequency is equal to
Displacement

t
0
0.5s

(1) 2Hz (2) 4Hz (3) 5Hz (4) 10Hz (5) 2.5Hz

25) A solid ball is released from rest down inclines of various inclination angles 𝜃 but
through a fixed vertical height h. The coefficients of static and kinetic friction are both
equal. Which of the following graphs best represents the total kinetic energy (Ek) of the
ball at the bottom of the incline as a function of the angle(θ) of the incline?
Ek Ek Ek
(1) (2) (3)

0 900 θ 0 900 θ 0 900 θ

Ek Ek

(4) (5)

900 θ 0 900 θ

Grade - 12 (2018) - March - 2017 6 Physics

 Part -II
Part A – Structured Essay
Answer all questions in this paper
(g = 10N kg-1)
01) An Experiment is made to determine the radius of a
capillary tube using mercury thread. Travelling
microscope, particular mass of mercury, Electronic
balance, a watch glass are given to you.
a) i. Identify the parts A,B,C,D of the travelling
microscope as shown in the figure below.
A :- .......................................................................
B :- .......................................................................
C :- .......................................................................
D :- .......................................................................
ii. What is the initial adjustment for this instrument?
.....................................................................................................................................
.....................................................................................................................................
iii. Give a method to insert mercury into the capillary tube.
.....................................................................................................................................
.....................................................................................................................................
b) The length of the mercury thread was measured by using travelling microscope. Find
the least count of the microscope if its length of the main division is 0.5mm and the 49
divisions of the main scale were divided into 50 divisions of the vernier scale.
...........................................................................................................................................
...........................................................................................................................................
c) The figure illustrates the position for taking measurement
for the mercury thread in one position. Draw the correct
diagram that is seen when observed through the travelling
microscope.

Grade - 12 (2018) - March - 2017 7 Physics

 d) As observed in part (c), the figure nearby shows the
position of main scale and the vernier scale. What is
the reading?
......................................................................................................................................................................
......................................................................................................................................................................
e) Readings taken to determine the mass of mercury threads are m1, m2. Identify these
two readings.
m1 ...........................................................................................................................................................
m2 ...........................................................................................................................................................
f) One student suggests using water thread instead of mercury thread. State two reasons
mentioning that using water thread is unfit.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
g) Consider the length of mercury thread is 4.000cm, what is the fractional error caused
during the measurement of length mercury thread?
...........................................................................................................................................
...........................................................................................................................................
02) The motion of a long jumper during a jump is similar to that of a projectile moving under
gravity. The figure shows the path of an athlete above the ground during a long jump from
half-way through the jump at position A, to position B at which contact is made with sand
on the ground. The athlete is travelling horizontally at A and the horizontal displacement
of the centre of mass from A to B is measured by a measuring tape which is calibrated in
cm scale as shown in the figure.(neglect the air resistance)

a) i. What is the horizontal displacement of the centre of mass of the athlete from A to
B?
.....................................................................................................................................

Grade - 12 (2018) - March - 2017 8 Physics

 ii. What is the estimate error of the measurement?
.....................................................................................................................................
.....................................................................................................................................
b) i. During this part of the jump, the centre of mass of the athlete falls 1.25m, calculate
the time taken for the centre of mass to move from A toB .
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
ii. Find the velocity of the athlete at A.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
iii. Find the horizontal and vertical velocities of the athlete at the point of jumping.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
c) i. The athlete slides horizontally through the sand a distance of 0.41m before
stopping. Calculate the time taken for the athlete to stop sliding. (Assume that
the horizontal component of the resistive force from the sand is constant)
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
ii. The mass of athlete is 75 kg. Calculate the horizontal component of the resistive
force from the sand.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
iii. Why the athlete stretched his legs and hands while landing on the sand?
.....................................................................................................................................
.....................................................................................................................................

Grade - 12 (2018) - March - 2017 9 Physics

 03) Figure shows a modified U tube experimental set up
to compare the densities of two liquids A and B,
employing a third liquid C which is immiscible with
both A and B. The level xy of the liquid C in the two
liquid A liquid B
arms of the U tube is horizontal.
(density d1) h1 (density d2)
a) Write down the inequality relationship among the h2
x
x
densities of these liquids (d1, d2 and d3) x y
liquid C
................................................................................ (density d3)
b) Suppose that the levels of liquids A and B above xy are h1 and h2 respectively. Write
down an equation relating h1,h2, d1 and d2
...........................................................................................................................................
c) Why is it necessary to maintain xy horizontal?
...........................................................................................................................................
d) i. State the experimental procedure to determine the ratio of the densities of d1 and d2
using graphical method (sufficient amount of liquids are available).
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
ii. Comment on the accuracy the measurements of h1 and h2 when the density of C
differs very much than that of A or B.
.....................................................................................................................................
.....................................................................................................................................
e) i. Draw a rough sketch of the straight line graph denoting h1 and h2 on the x and y
axis respectively.

ii. The gradient of the straight line is as 0.8 when A, B and C are chosen as water
(density 1000Kgm-3), copper sulphate solution and mercury (density 13600kgm-3)
respectively. Find the density of the copper sulphate solution.
.....................................................................................................................................
.....................................................................................................................................

Grade - 12 (2018) - March - 2017 10 Physics

 iii. If it is desired to measure the height of the liquid column with an accuracy less
than 1% what will be the minimum height of the liquid column.
.....................................................................................................................................
.....................................................................................................................................

04) During the hot day, A student tended to determine the speed of sound in
air (v) and the end correction (e) using the structure expelling water
from the tube and the tuning fork with known frequency as shown in the
diagram.

a) Mention the additional items that are necessary to carry out the
experiment effectively for that student?

..............................................................................................................
..............................................................................................................

b) State the practical that he has to follow to vibrate the tuning fork?
...........................................................................................................................................
c) Give the procedures that the student has to do in order to get fundamental resonance
state.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
d) What is the medium and periodic force in this experiment?
i. medium :- ..........................................................................................................

ii. periodic force :- ..........................................................................................................

e) Draw the structures of wave of first two resonance states including the end correction
on the sketch given below.

Grade - 12 (2018) - March - 2017 11 Physics

 f) Find the end correction of the tube and the speed of sound in air if the length of the
first two resonance as mentioned in part (e) are 17cm, 49cm respectively.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
g) If alcohol is used instead of water, the speed of sound and end correction calculated in
part (f) would be changed. (assume the environmental temperature is constant).
speed of sound : .......................................................................................................

Explanation : .......................................................................................................
.......................................................................................................

End correction : .......................................................................................................

Explanation : .......................................................................................................

.......................................................................................................

Grade - 12 (2018) - March - 2017 12 Physics

 Part -II
Part B – Essay
Answer two questions only

01) A flywheel is made by joining two large discs together with a smaller disc of radius 20
mm in the middle and it is free to rotate about an axis passing through their centres. A
light, thin cord is wound round the inner disc 8 times as shown in figures 3 and 4.

20 mm

400 N
Figure
When the flywheel is at rest a steady force of 400 N is applied at the end of the cord and it
unwound fully in 4.0 seconds. (Take π = 3)
a) i. Calculate the angular acceleration of the flywheel;
ii. Calculate the maximum angular velocity attained by the flywheel;
iii. Sketch a graph showing the variation of angular velocity with time;
iv. Sketch a graph showing the variation of angular displacement with time and
v. Calculate the work done by the applied force on the flywheel.

b) There is always a constant frictional torque of 2.0 Nm comes into action when the
flywheel is rotating about its axis.
i. Calculate the moment of inertia of the flywheel.
ii. When the cord is fully unwound, it detaches from the flywheel.
Calculate the angular deceleration of the flywheel;
iii. Calculate the duration of time for which the flywheel was in rotation.

c) When thin cord is now replaced with a light but thicker cord of same length, the
overlapping of the cord itself, as shown in figures, when wounded on the inner wheel.

20 mm

400 N
Figure

Grade - 12 (2018) - March - 2017 13 Physics

 i. A steady force of 400 N is applied at the end of the cord as before. Will the time
taken by the thicker cord to unwrap and detach from the flywheel be longer, shorter
or same as for the thin cord? Support your answer with explanation.
ii. What is the purpose for which flywheels are used in automobile engines?

Torque (Nm)

30

10
0 Angle (rad)
𝜋/4 3/4𝜋 𝜋 2𝜋

d) The variation of resisting torque on the rotating shaft driving the needle of an electric
sewing machine is shown above. A stitch is made for each cycle of operation and for
every second it makes 2 stitches. The efficiency of the sewing machine and the electric
motor are 78% and 40% respectively.
Calculate
i. The amount of work done by the sewing machine during a cycle of operation;
ii. The useful power output by the sewing machine;
iii. The power supplied by the electric motor to the sewing machine;
iv. The power drawn by the motor from the electrical power source;
v. The total consumption of electrical energy in kWh if sewing is done for 2000 h.

02) a) i. State the necessary and sufficient conditions under which Bernoulli’s principle
can be applied for a fluid flow.
ii. Write down the Bernoulli’s equation in usual symbols and identify the symbols
used in the equation.
iii. When an incompressible fluid flow from wider tube to narrow tube, what happens
to
α) the speed of the fluid?
β) the pressure of the fluid?
iv. How the upward lift in an aeroplane is achieved on flight ?
v. A cricket ball is thrown by a bowler towards the batsman. Sketch the path taken by
the ball in a wind free day when the ball is thrown
α) without spin,
β) with backward spin, and
ϒ) with forward spin.

Grade - 12 (2018) - March - 2017 14 Physics

 A
b)
Reservoir
; B

LBC=16m 60o
dBC = 200 mm C
o
60o 60
LCD = 20 m LCE = 30 m, dCE = 50 mm

D dCD = 100 mm

E
The figure above shows a large water reservoir (A) on a hill which supplies water for
the irrigation of vegetable farms in a valley. The depth of water in the reservoir is 2 m.
The lengths of the water supply pipes BC = 16 m, CD = 20 m and CE = 30 m. The
diameters of the pipes BC, CD and CE are 200 mm, 100 mm and 50 mm respectively.
All three supply pipes are fixed in a vertical plane and each of them make 60o with the
vertical.(Assume that the water is a non viscous fluid and √5 = 2.24)
i. Find the speed of water
α) at the outlet point D,
β) at the outlet point E.
ii. Find the flow speed of water in the pipe BC.
X
D
Water
Outer wall of the canal
Canal
Y
Water Z

Grade - 12 (2018) - March - 2017 15 Physics

 c) The water from the outlet D of the pipe CD is completely delivered to end X of a
horizontal irrigation canal XYZ having a rectangular cross section of width 150 mm.
There is no splashing of water from the canal. (Assume π = 3)
Calculate the following:
i. The volume rate of delivery of the water into the canal.
ii. The height, h, of water in the canal assuming that the speed of the water in the
canal is same as that of the delivery speed at the outlet D.
iii. The mass rate flow of the water in the canal. ( The density of water = 1000 kgm-3)
iii. Find the thrust exerted on the outer wall Y due to the flow of water.

03) Read the following passage and answer the questions.

Sesmic waves are the waves of energy caused by the sudden breaking of rock within the
earth or an explosion. These sesmic waves travel in all directions from the point where the
energy is released, and this point is known as the focus of the earthquake. The
corresponding point on the Earth’s surface directly above the focus is called epicentre of
the earthquake.
The waves which travel through the earth’s inner layers are called body waves and those
travel on the earth surface are called surface waves. The frequency of the body waves
higher than surface waves. The body waves consist of P waves and S waves. P waves are
longitudinal waves whereas the S waves are transverse waves.
The P waves from an earthquake arrive at a given location before S waves and surface
waves, the P waves can travel through any kind of any material, solid or fluid, S waves do
not exist in a fluid. Richter scale is most accepted method used to estimate the strength of
an earthquake. Most tsunamis are caused by underwater earthquakes. Some of them are
caused a volcanic eruption, an Sub-marine, rock slide and an asteroid or meteoroid
crashing into in the water, from space. The wave length of tsunami is very high in deep
ocean that is wave length of tsunami is greater than depth of the deep ocean, than the
speed of tsunami is given by V= gh where h - depth of the ocean, g - gravitational
acceleration.
a) Why seismic waves incidence occurs in the earth?
b) What do you mean by the focus of the earthquakes?
c) What is the relationship between focus and epicentre of an earthquake?
d) Compare the properties of S and P waves. (at least three)
e) Arrival time difference of P and S waves from epicentre to seismic data recording
station is 50 sec, speed of the P and S waves are 5kms-1 and 3kms-1 respectively. Find
the distance of the epicentre from the data recording station.
f) What is the scale for measuring strength of earthquake?
g) i) How do most of the tsunami waves creates in Earth?
ii) Whether tsunami waves, longitudinal or transverse waves?

Grade - 12 (2018) - March - 2017 16 Physics

 h) The speed of a tsunamis 720kmh-1in the open ocean and the wave length 6km long.
i) Find the depth of the open ocean.
ii) What is the period of oscillating of the tsunami wave?
iii) The maximum vertical oscillating speed of the ship is 0.4ms-1 in the open ocean
while the engine of the ship ceased and couldn’t move forward. Find the amplitude
of oscillation of the ship. (take π = 3)
iv) What is the minimum vertical oscillating speed of the ship?
v) Draw a rough sketch of the kinetic energy (Ek) of the ship verse time (t) graph for
the period of a oscillation. (Consider at time t = 0 the ship oscillates minimum
vertical speed)

Grade - 12 (2018) - March - 2017 17 Physics