Download SECTION B ( 48 marks )

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CCC Hoh Fuk Tong College
Mock Examination 2003 - 2004
Physics II
Secondary : 7S
Time allowed : 3 hrs. ( 1:00 p.m. - 4:00 p.m. )
Name : __________________________
Date : 1 / 3 / 2004
Max. marks : 93
Class : 7S
Class. No. : ____
This paper must be answered in English
SECTION A : Multiple Choice Questions - Answer ALL Questions
SECTION B : Answer Any THREE Questions
INSTRUCTIONS FOR SECTION A
1. All the answers should be marked on the Answer Sheet.
2. Note that you may only mark ONE answer to each M.C. question. Two or more
answers will score NO MARKS.
3. All questions carry equal marks. No marks will be deducted for wrong answers.
SECTION A ( 45 marks )
There are 45 questions in this section. Answer ALL questions. Each of the questions is
followed by four suggested answers. Select the best answer in each case. Where necessary,
take g = 10 m s-2 and take c to be 3 x 108 m s-1.
1. Which of the following is equivalent of a unit of energy
(1) kilo-watt hour
(2) electron volt
(3) newton-metre.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (1), (2) and (3)
2. An object is thrown horizontally from the top of a cliff at a speed 20 m s-1 .What will
be the speed of the object after 3 s ?
A. 10 m s-1
B. 25 m s-1
C. 30 m s-1
D. 36 m s-1
.
3.
Two bodies P and Q are connected by a light string A. The weights of P and Q are 6 N
and 10 N respectively. P is connected to the roof by another light string B. If string B is
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cut and the bodies allowed to fall, the net force acting on P during free fall is
A.
B.
C.
D.
2N
4N
6N
16 N
4.
An object of mass 3 kg is tied to another object of mass 2 kg with a string passing
over a fixed smooth pulley. The weight of the pulley is negligible. When the objects
move under the action of gravity, the vertical upward force acting on the axle of the
pulley is
A. 10 N
B. 24 N
C. 48 N
D. 50 N
5. A motor-cycle stuntman with mass 50 kg travels around the inside of a sphere of
radius 3m.
What is the minimum speed he must have at the lowest point of his path so that he
may remain in contact with the sphere at all times ?
A.
B.
C.
D.
3.87 m s-1
5.48 m s-1
11.0 m s-1
12.2 m s-1
6. When a constant torque T is applied to a flywheel which is accelerated from rest for
10 s, the rotational k.e. of the flywheel is E. If the constant torque T is now applied
to the same flywheel for 30 s, the new rotational k.e. of the flywheel will be
A. 1.5 E
B. 3 E
C. 4.5 E
D. 9 E
7. A 0.1 kg mass suspended from a light helical spring oscillates with vertical simple
harmonic motion of amplitude 2.5 cm. If the maximum kinetic energy of the mass is
3.0 x 10-3 J, its frequency of oscillation is
A. 0.5 Hz
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B. 1.6 Hz
C. 3.2 Hz
D. 16.0 Hz
8. A body hanging on a light spring oscillates vertically between level X and Z as
shown below. Its static equilibrium position is at level Y.
Which of the following statements is/are correct ?
(1) The acceleration of the body is zero when it is at level X.
(2) The strain energy of the spring is zero when the body is at level Y.
(3) The net downward force acting on the body is at its maximum when it is at
level Z
A. (1) only
B. (3) only
C. (1) and (2) only
D. (1), (2) and (3)
9. Assuming the Earth to be a perfect sphere, what would be its angular velocity of
rotation for an object at the equator to be weightless ( i.e. to give a spring balance
reading of zero ) ?
( Radius of the Earth = 6.4 x 106 m )
A. 2.4 x 10-12 rad s-1
B. 1.6 x 10-6 rad s-1
C. 1.3 x 10-3 rad s-1
D. 8.0 x 102 rad s-1
10. The least separation between 2 points with a phase difference of /3 on a progressive
wave is 0.05 m. If the velocity of the wave is 150 ms-1, the frequency of the wave is
A. 200 Hz
B. 300 Hz
C. 500 Hz
D. 600 Hz
11.
A stationary sound wave vibrating in its fundamental mode is set up in an open tube .
P and Q are two points at the end and the middle of the tube along its axis.
Neglecting end-correction, what is the phase difference between the vibration of the
air molecules at points P and Q ?
A.
B.
C.
D.
0
/4 radian
/2 radian
 radian
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12.
The figure shows an object O placed at the focus of a converging lens L. A concave
mirror M is arranged on the other side of L and is 80 cm from it. If the focal length
of L is 60 cm and the final image formed by this system is at infinity, what is the
focal length of M ?
A.
B.
C.
D.
10 cm
20 cm
40 cm
80 cm
13. A plane transmission grating is placed at the center of a circular 0o – 360o protractor.
A beam of monochromatic light is incident normally on the grating. The
zeroth-order maximum occurs at a scale reading of 80o and a first-order maximum
occurs at a scale reading of 55o. At what scale reading would a second-order
maximum be observed ?
A.148 o
B. 138 o
C. 130 o
D. 58 o
14. Which of the following statements is/are incorrect ?
(1) All standing waves are transverse waves.
(2) Ultrasonic waves can be polarized.
(3) Microwaves can be polarized.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (1), (2) and (3)
15. A hydrogen source in a laboratory emits a line spectrum with one of the lines having
wavelength 656.3 nm. For a star receding from the earth at a speed of 200 km/s,
what would be the wavelength of the corresponding line from the star observed on
the earth ?
A. 655.5 nm
B. 655.9 nm
C. 656.7 nm
D. 657.1 nm
16. A radio produces a sound of intensity level 40 dB at a point 5 m away from it. If
there are three identical radios placed and sounded together, what is the intensity
level in decibel 20 m from them ? ( The radio can be regarded as a point source )
A. 10 dB
B. 28 dB
C. 33 dB
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D. 38 dB
17. Sunlight is scattered by air molecules in the atmosphere. Which of the following
statements concerning this process is/are correct ?
(1) Light is absorbed by air molecules and is then re-emitted.
(2) The scattered light observed on the earth's surface is completely plane-polarized.
(3) Red light is scattered more than blue light is.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (1), (2) and (3)
18.
Two microscope glass slides are arranged so that at one end they are in contact. At
the other end, they are separated by a piece of metal foil 0.020 mm thick. The slides
are 10 cm long. When the slides are illuminated normally with light of wavelength
500 nm, what is the spacing of the interference fringes formed by reflection ?
A.
B.
C.
D.
0.25 mm
0.50 mm
1.25 mm
5.00 mm
19. If the fundamental frequency of a closed pipe is 300 Hz, what is the first overtone for
this closed pipe ?
A. 150 Hz
B. 450 Hz
C. 600 Hz.
D. 900 Hz
20.
The figure shows a pattern of electric field lines in which P, Q and R are points
marked on one of the field lines with PQ=QR. If the potential at P is 0V, which of
the following can give the possible potentials at Q and at R?
A.
B.
C.
D.
Potential at Q
-100 V
-100 V
+100 V
+100 V
Potential at R
-200 V
- 300 V
+ 200 V
+ 300 V
21. A charged particle is accelerated across the gap between two parallel metal plates
maintained at a certain potential difference in a vacuum. Assuming there is no
gravitational force, the energy acquired by the charged particle in crossing the gap
depends on
(1) the potential difference between the plates.
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(2) the magnitude of charge of the charged particle.
(3) the width of the gap
A. (1) only
B. (3) only
C. (1) and (2) only
D. (1), (2) and (3)
22. A charged capacitor is connected across a resistor. Its voltage drops to one-third of
the original value in 10 s. Find the time constant of the circuit.
A. 4.1 s
B. 9.1 s
C. 11 s
D. 25 s
23.
A 4 F capacitor, which is initially charged, is discharged through a 50  resistor.
The maximum current during discharge is 2 A. What is the initial energy stored
inside the capacitor ?
A. 2 J
B. 0.2 J
C. 0.1 J
D. 0.02 J
24. A cell of e.m.f. 1.5 V is connected in series with a variable resistor of resistance R
and an ammeter A of resistance 0. 6 . By varying R, a series of ammeter readings, I,
are taken and a graph of 1/I against R is plotted. The value of the y-intercept is found
to be 0.88 A-1. What is the internal resistance of the cell ?
A.
B.
C.
D.
25.
0.59 
0.72 
0.82 
1.32 
A lamp bulb is connected in series with a solenoid and an a.c. supply. Which of the
following methods can decrease the brightness of the lamp bulb ?
(1) Put a soft iron bar into the solenoid.
(2) Increase the number of turns of the solenoid.
(3) Increase the frequency of the a.c. supply, but the peak-to-peak voltage
remains constant.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (1), (2) and (3)
26. A power station supplies electrical power to a user. The power generated by the
station is 1200 kW and is transmitted at 132000 V. If the resistance of the lines
connecting the power station to the user is 550 , the power available to the user is
about
A. 700 kW
B. 1155 kW
C. 1195 kW
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D. 1200 kW
27.
In the above circuit, the battery has constant e.m.f. and negligible internal resistance.
If switch S is closed, what would happen to the electric potential at P and at Q ?
A.
B.
C.
D.
Potential at P
Increased
Increased
Decreased
Decreased
Potential at Q
Increased
Decreased
Increased
Decreased
28. An additional mechanical load is applied to a rotating motor. Which of the following
is/are true ?
(1) The motor will decrease in speed.
(2) More power will be drawn from the power supply
(3) The e.m.f. induced in the rotating coil will increase.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (1), (2) and (3)
29. The current in a coil changes steadily from 2 A to 5 A in 75 ms so that a back e.m.f.
of 1 V is induced in the coil. The self-inductance of the coil is
A. 0.025 H
B. 0.10 H
C. 10 H
D. 40 H
30.
A light rectangular wire frame ABCD moves with a uniform speed to the left across
a region of uniform magnetic field acting into paper. Which of the following is/are
true at the instant shown in the figure ?
(1) A current is flowing in the clockwise direction.
(2) The electric potential at B is higher than that at C.
(3) The side AD experience a magnetic force acting to the right.
A. (1) only
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B. (3) only
C. (1) and (2) only
D. (1), (2) and (3)
31. The figure below shows an aluninium ring which floats above a coil which is
carrying an alternating current.
Which of the following changes alone will make the ring float at a greater height
above the coil ?
(1) Increase the frequency of the alternating current.
(2) Make the ring thinner and with a larger radius.
(3) Replace the ring with another one made of copper and of identical shape and
mass.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (1), (2) and (3)
32.
The above diagram show a rectangular current-carrying coil ABCD in a uniform
magnetic field between two pole pieces. The magnetic field is perpendicular to the
plane of the coil. Which of the following statements is/are correct?
(1) There is a magnetic force acing on the side AB of the coil.
(2) The magnetic forces acting on the coil tend to increase its area.
(3). The coil will return quickly to its original vertical position when it is disturbed
slightly.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (1), (2) and (3)
33. Two different ideal gases, A and B, are contained in two identical vessels. If the
ratio of their absolute temperatures and the ratio of the root-mean-square speed of
the molecules are respectively 2:1 and 3:2, the ratio of their molecular masses is
A.
B.
C.
D.
2:3
8:9
2:9
8:3
34. 1 mole of an ideal mono-atomic gas expands at a constant pressure of 105 Pa from a
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volume of 0.02 m3 to a volume 0.03 m3. The increase in internal energy of the gas is
A. 500 J
B. 1000 J
C. 1500 J
D. 2500 J
35. A uniform wire is stretched under tension. The strain in the wire depends on
(1) the cross-sectional area of the wire.
(2) the Young modulus of the wire.
(3) the unstretched length of the wire.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (1), (2) and (3)
36. A sheet of aluminium is moved toward the north pole of a bar magnet. Which of the
following statements is/are correct ?
(1) Eddy current flows in the sheet.
(2) Temperature of the sheet increases.
(3) Attractive force is experienced by the magnet.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (1), (2) and (3)
37. The armature of a d.c. electric motor has resistance 2 . When the applied potential
difference is 150 V, a current of 5 A flows. The back e.m.f. is
A. 10 V
B. 93 V
C. 140 V
D. 150 V
38. X and Y are two long solenoids having the same length and the same cross-sectional
area. They are wound on the same type of core material. X has 500 turns and Y has
1 000 turns. If the self-inductance of X is 0.5 H, the self-inductance of Y is
A. 0.5 H
B. 0.7 H
C. 1.0 H
D. 2.0 H
39.
In a Hall probe, the slice of semiconductor inside has 1025 charge-carriers per cubic
metre. When a steady current of 0.4 A passes through the slice and a uniform
magnetic field of 0.1 T applies perpendicularly to it, a Hall voltage of 17 V is set
up. Find the thickness of the slice. ( Given : electronic charge = 1.6 x 10-19 C)
A.
B.
C.
D.
0.9 x 10–3 m
1.1 x 10-3 m
1.3 x 10-3 m
1.5 x 10-3 m
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40.
In the above circuit, the output voltage from the operational amplifier is negative.
Which of the following changes could causes the output voltage to change to
positive ?
(1) Increasing the value of R1.
(2) Increasing the value of R3
(3) Decreasing the light intensity on the LDR.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (1), (2) and (3)
41.
The diagram shows some energy levels ( drawn to scale ) of a certain atom. Transition
X results in the emission of a photon of wavelength 600 nm. Which transition ( P to
S ) would result in the emission of a photon of wavelength 300 nm ?
A. Q
B. R
C. S
D. T
42. Electron transitions occur in an atom resulting in the emission of the following light
wavelengths :
from level C to level A : 600 nm
from level B to level A : 500 nm
Which of the following statements is/are correct ?
(1) Level A has a lower energy than both levels B and C.
(2) Level C has a higher energy than level B.
(3) The wavelength of light emitted for the transition between C and B is 100 nm.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (1), (2) and (3)
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43. A radioactive sample, initially consists of only nuclide X, decays by the emission of
an alpha particle to form a stable daughter nuclide Y. Which of the following
quantities will decrease with time ?
(1) The rate of decay of nuclide X.
(2) The rate of growth of nuclide Y.
(3) The rate of emission of alpha particles.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (1), (2) and (3)
44. A counter is placed nearly a very weak radioactive source which has a half-life of 1
hour. The counter registers 100 counts/min at noon and 80 counts/min at 1 p.m. The
expected count rate, in counts/min, at 3 p.m. on the same day is
A. 50
B. 55
C. 60
D. 65
45. Given : mass of proton = 1.0073 u, mass of neutron = 1.0087 u
binding energy of an alpha particle = 28.396 MeV
1 u is equivalent to 931 MeV
The mass of an alpha particle is
A. 3.9100u.
B. 4.0015 u
C. 4.0320 u.
D.4.0625 u
END OF SECTION A
SECTION B ( 48 marks )
Answer any THREE questions from this section. Write your answers in the
ANSWER BOOK provided. You should spend 1 hour and 15 minutes on this
section.
1. a. State the principle of conservation of liner momentum
( 1 mark )
b. i. By considering the apparatus that can be found in a school laboratory, describe an
experiment to verify the principle of conservation of linear momentum.
( 6 marks )
ii. The principle of conservation of momentum is consistent with Newton’s law of
motion. By considering the collision of two objects, show that Newton’s third
law can be derived from conservation of linear momentum.
( 5 marks )
c. For the following situations, briefly explain whether the total momentum is
conserved and state the origin of the forces.
i. The moon move in an orbit with the Earth as one of the centre of the orbit.
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ii. an  particle collide with a gold atom and then rebound.
( 4 marks )
2. a. Plane monochromatic light waves of wavelength  are incident normally onto a
plane transmission grating of slit separation d to produce an interference pattern.
i. Using the principle of superposition describe briefly how the principal maxima
are formed and deduce the formula for the angular positions of the principal
maxima.
ii. It is preferable to measure the wavelength of light by using a plane transmission
grating rather than using a double slit. Explain briefly.
( 5 marks)
b. Describe an experiment for observing the absorption spectrum of iodine using a
diffraction grating. Describe the spectrum observed and account for it in terms of
the quantum nature of light and atomic structure.
( 8 marks)
c. Briefly explain the principles involved in identifying the elements present in the
atmosphere of the sun through studying the sun’s spectrum.
( 3 marks)
3. a. A parallel-plate capacitor of capacitance C and a resistor of large resistance R are
connected in series with a battery of e.m.f. having negligible internal resistance.
i. Sketch graphs to show the time variation of the voltage, across the capacitor and the
current in the circuit after closing switch S. Briefly explain your answer.
ii. A student uses a voltmeter of resistance R to check the voltage across the capacitor
and finds that the reading falls from an initial value to a final steady value /2.
Briefly explain why this is so.
iii With switch S closed, the plates of the capacitor are pulled apart slightly. Describe
and explain the possible change(s) in the charge and the energy stored in the
capacitor when the steady state is reached.
( 8 marks )
b. i. You are asked to demonstrate the change in the terminal p.d. of a supply when
delivering a current. With the aid of a diagram, describe how you would carry out
the experiment using a 12 V 24 W ray box lamp and some additional apparatus.
Explain how the internal resistance of the supply could be estimated and state the
source(s) of error.
ii (I) State and discuss the significance of the order of magnitude of the internal
resistance of a 5 kV E.H.T.
(II) A 12 V car battery is designed to deliver a current of a hundred amperes to
operate the starting motor. Explain why the headlights would dim when a car is
started with the headlights on.
( 8 marks )
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4. a. There are 2 principles involve in electromagnetic induction: the Faraday’s Law and
the Lenz’s law. By considering a straight conductor moving in a uniform magnetic
field, describe how these 2 principles determine the induced e.m.f.
( 4 marks )
b. i. Derive the following relation for a transformer : Np : Ns = Vp : Vs, where Np ,Ns,
Vp and Vs are the number of turns of coil of the primary coil ,the secondary coil,
the voltage across the primary coil and secondary coil respectively.
( 2 marks )
ii. The following is a block diagram for a transformer. When the switch K in the
secondary coil is closed, describe the effects on the magnetic field line, and the
energy change take place in the primary and secondary coil.
( 6 marks )
iii. Describe, with explanation, TWO methods to increase the efficiency of a
transformer.
( 4 marks )
5. a. To detect radiations, a GM tube is an useful apparatus. Briefly discuss its structure
and also the working principle the GM tube. Also discuss the suitability of a GM
tube for detecting particles,  particles and  radiation.
( 7 marks )
b. i. Sketch a graph of binding energy per nucleon against mass number and use it
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U nucleus is not as stable as a 56
Fe nucleus.
to explain why 235
ii. Why energy would be released when hydrogen nuclei fused to form helium
nuclei ?
( 4 marks )
c. Sketch the basic structure of a nuclear power station. Explain the functions of
i. the moderator,
ii. the control rod, and
iii. the coolant.
( 5 marks )
*** END OF PAPER ***