13/2/P.1/T11
YU CHUN KEUNG MEMORIAL COLLEGE NO.2
Mock Examination ( 2005 – 2006 )
F.7 Physics ( II )
Time allowed: 3 hrs.
This paper consists of two sections: Section A and Section B.
Section A : Multiple-choice Questions – Answer ALL Questions.
Section B : Answer Any THREE Questions.
Section A
All the answers should be marked on the M.C. answer sheet
1. A man running towards the north
feels that the wind comes from
gain in
work done against
kinetic
friction/J
energy/J
north – east. Which of the following
diagrams correctly shows the actual
A.
25
0
direction of the wind?
B.
25
25
C.
50
cannot be
A
B
C
D
determined
D.
2.
50
0
3. A box moves at a uniform velocity of
sphere
30
2 m/s on a frictionless horizontal
surface. Sand falls into the box with
o
negligible speed at a rate of 90 kg
per minute.
A sphere of mass 1 kg is released
What horizontal force
is required to keep the box moving
from rest on an inclined plane of
uniformly at 2 m/s?
inclination 30º to the horizontal (as
shown). If the sphere rolls without
slipping, find the gain in kinetic
energy and the work done against
friction by the sphere after travelling
a distance of 5 m along the plane.
1
A.
0N
B.
3N
C.
6N
D.
90 N
4.
undergoing simple harmonic motion
A conveyor belt is moving towards
may be increased by
the right at a constant speed of 10
ms-1. Sands are dropped with
A. using a heavier pendulum bob.
negligible speed at the rate of 90 kg
B. increasing
per minute. What is the power input
oscillation.
of the belt?
the
amplitude
of
C. placing the pendulum at the top
of a mountain.
A.
15 W
B.
60 W
C.
150 W
D.
9000 W
D. placing the pendulum at the
North Pole.
7. A particle oscillates with simple
harmonic motion along a straight
5.
line with amplitude A.
When the
displacement of the particle from its
O
O
equilibrium position is ½A, its speed
O
is u.
The speed of the particle when
passing the equilibrium position is
The above diagram shows a uniform
hollow metal sphere with a small
A.
2u/3
opening on top.
O is the position of
B.
2 u
the centre of mass of the hollow
C.
3 u
sphere.
D.
2u
What will happen to the
position of the centre of mass of the
system as the sphere is being slowly
8.
filled with oil from the opening?
A
A. It will fall gradually, and its final
position will be below O.
P
B. It will fall gradually at first and
then rise to its original position.
C. It will rise gradually and its final
The figure shows a small heavy bob P
position will be above O.
attached to a fixed point A on the
D. It will rise gradually at first and
ceiling by a light inextensible string.
then fall to its original position.
The bob is pulled aside with the
string taut and then released from
rest.
6. The period of a simple pendulum
Which
of
the
descriptions is/are true?
2
following
A.
3 V0/2
(1) When moving towards the lowest
B.
2V0
point of its path, the angular
C.
6 V0
speed of the bob is increasing.
D.
23 V0
(2) The centripetal acceleration of
the bob is constant.
11. For planets or satellites in circular
(3) When the bob is at the lowest
orbits around a celestial body such
point, the tension in the string
as the sun or the earth, the period T
equals the centripetal force.
is related to the radius of orbit r by
Kepler's 3rd law T² =
kr³ where k is
A.
(1) only
a constant.
B.
(3) only
C.
(1) and (2) only
Which of the following statements
D.
(2) and (3) only
concerning the constant k is correct?
A. It is a dimensionless constant
9. A ring of radius a is made from thin
whose value is not affected by
wire. The moment of inertia of the
the choice of units.
ring about an axis through its centre
B. It is a universal constant whose
and perpendicular to its plane is I.
value is not affected by the
What would be the moment of inertia
choice of units.
of a ring, made from the same type
C. It is a universal constant whose
of wire but with radius 2a, about a
value depends on the choice of
similar axis?
units.
D. It would have a certain value for
A.
I
all planets moving around the
B.
2I
sun, but a different value for all
C.
4I
satellites
D.
8I
earth.
moving
around
the
12. A communication satellite appears
10. The velocity of escape from the earth
stationary
vertically
above
an
is V0. For a planet with radius twice
observer at the equator. The height
that of the earth and with density
of the satellite above the observer is
three times that of the earth, the
3.6  107 m. Calculate the mass of
velocity of escape from the planet
the earth.
would be
3
Given:
Radius of the earth = 6.4  106 m
Gravitational constant = 6.7  10-11
The above figure shows a Pitot-static
Nm2kg-2
tube situated in a moving fluid.
Which of the following graphs best
A.
4.5  1024 kg
shows
the relation
B.
5.0  1024 kg
speed
v
C.
5.5  1024 kg
difference in manometer levels h?
D.
6.0  1024 kg
of
the
fluid
A.
13. Given that G = 6.67x10-11 Nm2kg-2.
v
The earth revolves around the sun
with
mean
orbital
radius
of
1.5x10 m. The mass of the sun is.
11
h
A.
1.2x1030 kg
B.
1.5x1030 kg
C.
1.8x10 kg
D.
2.0x10 kg
B.
30
v
30
14. A flywheel slows uniformly from
1000 rev min-1 to 250 rev min-1 in 5 s.
h
How many revolutions does it make
in this time?
C.
A.
52
B.
100
C.
330
D.
3100
v
h
15.
D.
v
fluid flow
speed v
h
h
4
between
the
and
the
C.
P
f
16. An ideal gas is contained in a
cylinder fitted with a light piston as
shown below:
i
V
D.
cylinder
P
IDEAL
GAS
i
piston
smooth
f
V
Initially, the piston is held fixed and
the gas is cooled.
Afterwards, the
17. An inexpansible vessel contains air
piston is pushed inwards slowly.
at 50 ºC.
Which
remains in the vessel if it is heated to
of
the
following
represents
the
variation
graphs
of
gas
100 ºC under constant pressure?
pressure P with gas volume V?
(
i
represents
initial
state;
What percentage of air
(You may take the ice point to be 273
f
K)
represents final state)
A.
A.
87%
B.
85%
C.
73%
D.
63%
P
f
18. Identical containers A and B contain
i
oxygen
(O2)
and
hydrogen
(H2)
respectively.
V
B.
O2
H2
P
Container A
f
i
Container B
Both gases are at room temperature
V
and atmospheric pressure.
Which
of the following statements is/are
true?
5
Room
Room
temperature on
temperature on
the resistance
the gas
thermometer
thermometer
scale/ºC
scale/ºC
A.
36
36
B.
cannot be
36
In both containers,
(1) the number of gas molecules is
the same;
(2) the r.m.s. speed of gas molecules
is the same;
(3) the frequency of collision of gas
molecules
with
the
walls
of
determined
container is the same.
C.
20
36
D
20
cannot be
A.
(1) only
.
determined
B.
(3) only
C.
(1) and (2) only
Samples of a monatomic gas P and
D.
(2) and (3) only
of a diatomic gas Q are nixed at the
20.
same
19. The calibration curve of a resistance
thermometer
against
a
temperature.
The
relative
molecular mass of P is 1/4 that of Q.
constant
The root-mean-square speed of the
volume gas thermometer is given
particles of P is n times that of Q,
below:
where n is
A.
Resistance / 
1/4
1.6
B.
1/2
1.5
C.
1
1.4
D.
2
1.3
21. The root-mean-square speed of the
1.2
1.1
particles of a gas at 500C is 500 ms-1.
0
20
40
60
80 100
What is the root-mean-square speed
Temperature / o C
of the particles of the gas at 1000C ?
When the resistance thermometer is
A.
500 ms-1
left in a room, its resistance if found
B.
537 ms-1
to be 1.28 .
C.
577 ms-1
D.
707 ms-1
room
Find the values of
temperature
on
both
the
resistance thermometer scale and
the gas thermometer scale.
6
22. Which of the following equations
correctly gives the relation between
the
polarising
angle
i
and
the
25. A radio produces a sound intensity
refractive index n of a material?
level of 50 dB at a point 2 m away
from it. If the power output of the
A.
sin i = n
radio is doubled, what is the sound
B.
n sin i = 1
intensity level at a point 6 m from the
C.
cos i = n
radio? (You may regard the radio as
D.
tan i = n
a point source)
23. An object placed in front of a
A.
30.9 dB
magnifying glass forms an image at
B.
43.5 dB
infinity with magnifying power 3.
C.
46.5 dB
What is the focal length of the
D.
48.2 dB
magnifying
glass?
(You
may
assume the least distance of distinct
26. A hydrogen source in a laboratory
vision to be 25 cm)
emits a line spectrum with one of the
lines having wavelength 656.3 nm.
A.
6.3 cm
For a star receding from the earth at
B.
8.3 cm
a speed of 200 km/s, what would be
C.
12.5 cm
the wavelength of the corresponding
D.
75 cm
line from the star observed on the
earth?
24.
(Velocity of light = 3  108
m/s)
displacement
time in seconds
0
0.20
0.45
0.70
A.
655.5 nm
B.
655.9 nm
C.
656.7 nm
D.
657.1 nm
A displacement-time graph of a
particle in a plane progressive wave
is
shown
above.
What
is
27.
the
soft
sound
frequency of this wave?
A.
1.43 Hz
B.
2 Hz
C.
2.22 Hz
D.
4 Hz
L
M
7
soft
sound
S
A loudspeaker L produces sound
B.
waves with frequency 1 000 Hz.
The sound waves are reflected from a
wall S.
When a microphone M is
moved
between
L
and
S,
the
loudness of the sound detected
varies. (Speed of sound in air = 340
C.
m/s)
Which of the following statements
is/are true?
(1) The variation in the loudness of
the sound is due to diffraction.
(2) The
separation
consecutive
positions
D.
between
of
soft
sound is 0.34 m.
(3) Increasing the sound frequency
will make the positions of soft
sound closer.
29.
A.
(1) only
B.
(3) only
C.
(1) and (2) only
D.
(2) and (3) only
a
b
B
A
28. An uncharged metal sphere is placed
in a uniform electric field. Which of
A positively-charged metal sphere A
the following best represents the
of radius a is joined by a conducting
electric field pattern around the
wire to an uncharged metal sphere B
metal sphere?
of radius b placed far away from the
first sphere. The ratio of the surface
charge density on sphere A to that on
sphere B is
A.
8
A.
b/a
B.
b²/a²
C.
a/b
D.
a²/b²
32. Which of the following devices is/are
30.
used to stored energy?
E
(1)
an inductor
(2)
a capacitor
(3)
a photocell
A.
(1) only
An initially uncharged capacitor of
B.
(3) only
capacitance C is connected in series
C.
(1) and (2) only
with a resistor R and a battery of
D.
(2) and (3) only
C
R
e.m.f. E. What will be (1) the total
work done by the battery in fully
33. Which
charging up C and (2) the energy
of
the
following
physical
quantities take(s) the unit ohm ()?
finally stored in C?
Work done by
Energy stored
battery
in C
(1)
resistance
(2)
reactance
(3)
impedance
A.
(1) only
A.
½CE²
0
B.
(3) only
B.
CE²
0
C.
(1) and (2) only
C.
½CE²
½CE²
D.
(1), (2) and (3)
D
CE²
½CE²
.
34. A motor is supplied with 100V. In a
certain case, a back e.m.f. of 75 V is
induced. If the coil resistance is 5 ,
31. The coil resistance of a 120V d.c.
motor
is 5 . It takes 4 A when
the efficiency of the system is
running without load. When bearing
a certain load, its speed is halved.
A.
6.25 %
What current does it now take?
B.
25 %
C.
50 %
D.
75 %
A.
2A
B.
4A
C.
8A
D.
14 A
9
35. Two insulated parallel metal plates
are connected to the terminals of an
The above figure shows two long
EHT.
parallel straight wires separated by a
When a charged aluminium
foil strip is placed between the plates,
distance of 0.2 m, carrying currents
deflection of the foil is observed as
of 1 A in opposite directions.
shown.
magnetic field at a point X mid-way
between
wires
is
(Given:
permeability constant 0 = 4  10-7
polystyrene
rod
metal
plate
the
The
TmA-1)
metal
plate
aluminium
foil strip
_
+
EHT
Which of the following statements
A.
0T
B.
2  10-6 T into paper
C.
2  10-6 T out of paper
D.
4  10-6 T into paper
37.
is/are true?
A
10 V
(1) The
charge
on
the
foil
M
is
negative.
(2) Deflection of the foil increases if
the
separation
between
A 10 V battery of negligible internal
the
resistance is applied to a d.c. motor
M with armature resistance 5 . If
plates decreases.
(3) When moving the foil towards the
the ammeter A of negligible internal
positive plate, the deflection of
resistance shows a reading of 0.4 A,
the foil increases.
the maximum useful output power
delivered by the motor is
A.
(1) only
A.
0.8 W.
B.
(3) only
B.
1.6 W.
C.
(1) and (2) only
C.
2.4 W.
D.
(2) and (3) only
D.
3.2 W.
36.
1A
X
0.2 m
1A
10
38.
39.
V1
0
time
primary coil
secondary coil
soft iron
bar
V2
0
Ip
current
source
time
A
B
Two coils are linked by a soft iron bar
Potential differences V1 and V2 are
as shown.
applied to the X-plates and Y-plates
connected to the primary coil. The
of a C.R.O. respectively.
primary current Ip varies with time as
The trace
on the screen is
A current source is
shown by the graph below:
A.
Ip
0
B.
t1
t2
time
Which of the following sketches
represents
the
variation
of
the
voltage across the secondary coil VAB
with time?
A.
C.
V AB
0
t1
t2
time
t1
t2
time
B.
D.
V AB
0
11
41.
V1 /V
C.
10
V AB
+15 V
0
1 2 3 4 time/ms
V1
V2
V2 /V
0
t1
t2
time
5
_
+
Vout
-15 V
0
1 2 3 4 time/ms
D.
V AB
Two electrical signals V1 and V2 are
fed into an operational amplifier.
The variations of V1 and V2 with time
0
t1
t2
time
are shown above.
following
graphs
Which of the
represents
the
variation of the output Vout with
time?
40.
A.
+6V
Vout
Vout / V
2k
6
15 k 
0
4
Vout
Vin
0V
time
2
0
1
2
Vin / V
B.
The above diagrams show an NPN
Vout
transistor circuit and its input/output
voltage characteristic.
What is the
0
time
current amplification factor of the
transistor?
A.
10
B.
30
C.
60
D.
75
C.
Vout
0
12
time
43. Which of the following materials
satisfies
D.
the
description:
ductile,
strong and stiff?
Vout
0
time
A.
steel
B.
diamond
C.
glass
D.
concrete
44. The
ionisation
potential
hydrogen atom is 13.6 V.
42.
of
a
What is
the minimum excitation potential of
a.c. supply
L
B
a ground state hydrogen atom?
C
A.
1.9 V
B.
3.4 V
C.
6.8 V
D.
10.2 V
The above figure shows an a.c.
circuit
with
a
filament
lamp
B
connected in series with a variable
inductor L and a capacitor C.
45. The spectrum of sunlight has dark
The
lines in it.
Which of the following
frequency of the a.c. supply can be
statements concerning these dark
varied. Initially the applied voltage
lines is/are correct?
leads the current in the circuit.
Which of the following methods will
(1) They are due to the absorption of
make the filament lamp B brighter?
certain wavelengths of light in
the sun’s atmosphere.
(1) Connect a capacitor in parallel
(2) Light
with C
absorbed
in
the
sun’s
atmosphere is re-emitted but in
(2) Increase the inductance of L
all directions.
(3) Decreases the frequency of the
(3) They are due to the absorption of
a.c. supply
certain wavelengths of light in
the earth’s atmosphere.
A.
(1) only
B.
(3) only
A. (1) only
C.
(1) and (2) only
B. (3) only
D.
(2) and (3) only
C. (1) and (2) only
D. (2) and (3) only
13
A. (1) only
46. An X-ray tube emits X-rays with a
B. (3) only
minimum wavelength of 3.55  10-11
C. (1) and (2) only
m. Estimate the potential difference
D. (1), (2) and (3)
between the cathode and the anode
(target) in the X-ray tube.
48. The number of radioactive nuclides
in two different samples P and Q are
Given: Planck constant = 6.63 
initially 4N and N respectively.
10-34 Js
the half-life of P is t and that of Q is
Electronic charge = 1.6 
2t,
10-19 C
the
number
of
If
radioactive
nuclides in P will be the same as the
Velocity of light in air = 3 
number of radioactive nuclides in Q
108 m/s
after a time of
A.
20 000 V
A.
t/2
B.
25 000 V
B.
t
C.
30 000 V
C.
2t
D.
35 000 V
D.
4t
47.
49.
 -particle
r0
atomic
nucleus
Q
P
P
The diagram shows an alpha-particle
ion source
‘colliding’ head-on with an atomic
nucleus. At P, the alpha-particle is
at the closest distance r0 from the
Two particles P and Q of same
nucleus.
quantity of charge and mass but
Which of the following
moving with different speeds vP and
statements is/are correct?
vQ respectively enter a region of
(1) At P, the electric potential energy
uniform magnetic field directed into
of the system is maximum.
the
plane
of
the
paper.
The
(2) r0 is of the order 10-14 m.
subsequent circular paths are as
(3) r0 gives an upper limit for the
shown.
sum
of
the
radii
of
the
Which of the following
statements is/are correct?
alpha-particle and the nucleus.
14
(1)
Both P and Q are positively
student measures the length of side l
charged.
and separation d of the plates.
(2)
vP is small than vQ.
(3)
The period of circular motion
If the maximum percentage error of l
of P is shorter than that of Q.
= 5%, the maximum percentage error
A. (1) only
of d = 3%, then the maximum
B. (3) only
percentage error for C will be
C. (1) and (2) only
D. (2) and (3) only
50.
A parallel-plate capacitor is formed
A.
7%
B.
8%
C.
13%
D.
22%
by two square metal plates. To
determine
the
capacitance
C,
a
- End of Section A -
15
Section B
Answer any THREE questions in the answer book.
1. (a) Describe simple harmonic motion (s.h.m.).
(2 marks)
(b) A simple pendulum consisting of a weight suspended vertically by
a string, of length l, attached to a fixed point is set in motion in a
vertical plane, the amplitude of oscillations being small. Show
that the motion is simple harmonic and write down expressions
for the displacement, velocity and acceleration of the weight after
a time t. Sketch the variations of potential and kinetic energies
with time.
(6 marks)
(c) Describe an experiment to verify that such a pendulum undergoes
s.h.m.
(6 marks)
(d) A student decides to use the oscillation of such a pendulum to
obtain a value for the free-fall acceleration due to gravity.
Without describing this experiment, critically discuss TWO
possible sources of error in your measurement.
(2 marks)
2. (a) Derive an expression for the acceleration experienced by a body
of mass m which is rotating with constant speed v around a
circular path of radius r, in the absence of any gravitational field.
(5 marks)
(b) Explain how each of the following cases is possible
(i) an aircraft flies along a circular arc in the sky.
(2 marks)
(ii) a centrifuge can be used to separate two liquids of different
densities.
(3 marks)
(c) (i)
(ii)
Sketch the expected variations of stress against strain for (1)
a copper wire, (2) a rubber band and (3) a glass fibre in a
Young modulus experiment, the loading being increased to
just before the materials break.
Briefly account for the different behaviour of the materials.
(6 marks)
16
3. (a) (i) Explain, with suitable diagrams, how to construct a transformer
for supplying 6V from 220V a.c. mains. State any assumptions
and explain why they are necessary.
(5 marks)
(ii)Explain how the input current changes when a resistor is
connected to the output terminals
(4 marks)
(b) Explain the use of an electron beam in a cathode ray oscilloscope.
Give a diagram showing the d.c. electrical connections but no
details of the beam focussing or electronic circuits are expected.
(5 marks)
(c) Suggest a possible hazard of sitting too near a colour television,
giving a brief explanation.
(2 marks)
4. (a) An a.c. voltage supply is connected across a coil of many turns,
this coil being placed over the vertical iron rod of a retort stand
and resting on the base.
Explain clearly your expected
observations, and the physical principles involved when
(i)
a small aluminium ring is dropped over and slides down the
vertical rod of the retort stand,
(ii)
the ring of (i) is replaced by a similar ring, but broken by a
vertical slot and
(iii) the ring of (i) is fastened down on top of the coil.
(6 marks)
(b) A series circuit is formed from a coil of inductance 500 H, a 2 V
light bulb, an open switch and a 2 V battery. Explain your
expected observations when
(i)
(ii)
the switch is closed and
after connecting a neon lamp across the coil, the switch is
opened.
(4 marks)
17
(c) Draw a circuit which can be used to observe the periodic
variations of current I together with those of an applied a.c.
voltage V for the coil of (b). Explain mathematically the phase
difference you would expect between I and V.
(6 marks)
5. (a) Explain how you would distinguish experimentally between , 
and -radiating radioactive sources using a Geiger-muller counter
detection system.
(6 marks)
(b) What changes take place in the constituents of the nuclei when
such radiations are emitted?
(3 marks)
(c) Explain your choice of type of radiation source, giving brief
details of use for
(i)
monitoring paper thickness, during manufacture,
(ii)
estimating the size of nuclei and
(iii) treating body cancer by destroying cancer cells.
(7 marks)
***** END OF PAPER *****
18
19
19
Section A
1.
2.
3.
4.
5.
A
A
B
C
B
26.
27.
28.
29.
30.
C
B
A
A
D
6.
C
31.
D
7.
8.
9.
10.
A
A
D
D
32.
33.
34.
35.
C
D
D
C
11.
12.
13.
14.
D
D
D
C
36.
37.
38.
39.
D
D
D
B
15.
A
40.
D
16.
17.
18.
19.
20.
A
A
A
C
D
41.
42.
43.
44.
45.
D
B
A
D
C
21.
B
46.
D
22.
23.
24.
25.
D
B
B
B
47.
48.
49.
50.
D
D
C
C
20