1980 Paper 2

Multiple-Choice Questions 1980 (1) When a constant unbalanced force is applied to a particle, which of the following will change with time ?

(1) the acceleration of the particle (2) the momentum of the particle (3) the kinetic energy of the particle A. (1) only D. (2) and (3) only

B. (3) only E. (1), (2) and (3)

C. (1) and (2) only

(2) A ball is dropped from a height h above the ground. Each time it hits the ground, one-half of the original kinetic energy is lost. How high will the ball rise above the ground after the second impact ? A. h/8 B. h/4 C. h/2 D. h/1.414 E. h (3) Two blocks A and B of masses m1 and m2 respectively are connected by a light spring on a horizontal frictionless table. The spring is stretched by moving the blocks apart. What is the ratio of the acceleration of A to that of B at the moment when they are released ? A. 1 : 1 B. m1 : m2 C. m2 : m1 D. m12 : m22 E. m22 : m12 (4) An object is resting on a rough plane inclined at an angle _ to the horizontal. As _ gradually increases, the frictional force acting on the object before sliding occurs is directly proportional to A. 1/θ B. θ C. sin θ D. cos θ E. tan θ (5) An object is thrown vertically upwards with initial speed u. Which of the graphs below represents the variation of its kinetic energy Ek with time t ? A

B

Ek

0

D

Ek

C

Ek

t

0

E

Ek

Ek

t

0

t

0

t

0

t

(6) Two objects P and Q of mass 2 kg and 3 kg respectively have tyhe same momentum. They are then subjected to the same constant resisting force and gradually brought to rest. What is the ratio of the stopping distance of P to that of Q? A. 4 : 9 B. 2 : 3 C. 1 : 1 D. 3 : 2 E. 9 : 4 (7) A horizontal force F is applied to a block of mass M on a rough horizontal surface. The acceleration of the block is a. If the force is changed to 2F and the frictional force remains unchanged, then the acceleration of the block will be A. greater than 2a B. equal to 2a C. between a and 2a D. equal to a E. less than a (8) In the figure below, X and Y are blocks of mass 1 kg anf 2 kg respectively. S is a spring balance of negligible mass and P is a smooth pulley fixed at the top of two smooth inclined planes. What is the reading of S when X is held stationary ?

M

F

p s

2kg

300

1kg

300

A. 5 N B. 10 N C. 15 N D. 20 N E. 30 N (9) A body is dropped from rest down a cliff on a planet X. After falling for 1s , it is 4 m below the starting point. How far below the starting point will it be after a further 4s ? A. 40 m B. 50 m C. 64 m D. 80 m E. 100 m

(10) A spring balance suspended from the ceiling of a lift registers the weight of a 20 kg body as 150 N. The lift is probably A. stationary B. ascending with uniform velocity C. ascending with uniform acceleration D. descending with uniform velocity E. descending with uniform acceleration (11) 6 x 10-3m3 of a gas is contained in a vessel at 91°C and a pressure of 4 x 105 Pa. If the density of the gas at s.t.p. (0°C and 105 Pa) is 1.2 kg/m3, what is the mass of the gas ? A. 7.2 g B. 14.4 g C. 21.6 g D. 28.8 g E. 38.4 g (12) Two bodies of the same volume have their specific heat capacities in the ratio 3:2, and their densities in the ratio 2:1. What is the ratio of their heat capacities ?

A. 1 : 3 D. 4 : 3

B. 3 : 4 E. 3 : 1

C. 1 : 1

(13) Air is trapped in a capillary tube sealed at one end. When the atmospheric pressure is 75 cm Hg, the length of the air column is 10 cm, as shown in the figure below. When the tube is inverted, what will be the length of the air column ?

A. 5 cm D. 20 cm

B. 10 cm E. 25 cm

C. 15 cm

(14) Two liquids A and B are cooled in air. Their cooling curves are shown below : temperature

A B time

If A and B have the same mass, which of the following statements is/are correct ? (1) A has a higher freezing point than B. (2) A has a greater specific latent heat of fusion than B. (3) Liquid A has a greater specific heat capacity than liquid B. A. (1) only B. (3) only C. (1) and (2) only D. (2) and (3) only E. (1), (2) and (3)

(15) When a mercury thermometer is immersed in melting ice and then in steam, the lengths of the mercury thread in the stem are respectively 2 cm and 22 cm. When the termometer is put in a water bath, the length of the thread is 11 cm. What is the temperature of the water bath ? A. 40°C D. 55°C

B. 45°C E. 60°C

(16) A light ray passes through a spherical air bubble in water. Which of the following represents the path of the emergent ray ?

C. 50°C

I water II III

A. I B. II C. III D. IV E. V

IV air water

V

(17) When light enters from one medium into another, which of the following will be changed ? (1) the frequency of light (2) the wavelength of light (3) the velocity of light A. (1) only B. (3) only C. (1) and (2) only D. (2) and (3) only E. (1), (2) and (3) (18) A point light source is placed in a liquid. Rays from the source leave the liquid surface through a circular area of diameter 24cm. The refractive index of the liquid is 1.25. The depth of the source below the liquid surface must be A. 9 cm B. 15 cm C. 16 cm D. 18 cm E. 32 cm (26) A convex lens is used to form an image of a bright object on a screen. The effect of covering the top half of the lens with a card is to A. remove the top half of the image B. remove the bottom half of the image C. make the image go out of focus D. make the image smaller E. make the image dimmer (27) A thick block of glass is placed on a book. When viewed from above the writing appears to have been lifted by 10 mm. If the refractive index of glass is 1.5, what is the thickness of the glass ?

A. 10 mm D. 25 mm

B. 15 mm E. 30 mm

C. 20 mm

(28) A fixed object is placed in front of a plane mirror. If the mirror is moved 0.10 m away from the fixed object, how far will the image move ? A. 0 m B. 0.05 m C. 0.10 m D. 0.20 m E. 0.40 m

(29) A concave mirror forms an erect image 28 cm from a real object. The image is 3 times as high as the object. The image is formed A. 7 cm behind the mirror B. 7 cm in front of the mirror C. 14 cm behind the mirror D. 21 cm in front of the mirror E. 21 cm behind the mirror (30) Which of the following statements about X-rays is/are correct ? (1) They can be deflected by an electric field (2) They consist of a stream of electrons (3) They may affect a photographic plate A. (1) only B. (3) only C. (1) and (2) only D. (2) and (3) only E. (1), (2) and (3) (31) A charged hollow pear-shape conductor has a sharp point S on the inside surface. It rests on an insulating stand as shown.The charge densities at P, Q, R and S listed in ascending order will be A. S R P Q B. P Q R S C. Q P S R D. Q P R S E. S Q P R (32) In the circuit below, what is the potential difference between points P and Q ? 4Ω

8Ω

P

Q

8Ω

4Ω

6V

A. 0 V D. 3 V

B. 1 V E. 4 V

C. 2 V

(33) In the circuit below, Y is a 5A fuse, Z and X are 3A fuses. When the switch K is open, the current passing through the 21 ohms resistor is 2.4A. When K is closed, which of the fuses will be blown ? Y D.C. source

A. X only D. X and Z only

Z

21Ω

X

18Ω

B. Y only E. X, Y and Z

K

C. Z only

(34) What is/are the advantage(s) of using high voltage and low current in power transmission over long distances ? (1) Thinner cables can be used (2) Less energy is wasted as heat. (3) Higher voltage can be used in household circuits. A. (1) only B. (3) only C. (1) and (2) only D. (2) and (3) only E. (1), (2) and (3) (35) An electromagnetic wave has a frequency of the order of 1016 Hz. The velocity of light is 3 x 108 m/s. The electromagnetic wave most probably consists of A. infra-red rays B. visible light C. ultra-violet rays D. X-rays E. gamma rays (36) Which of the following convert(s) electrical energy into sound energy ? (1) An electric bell (2) A loudspeaker (3) A telephone receiver A. (1) only B. (3) only C. (1) and (2) only D. (2) and (3) only E. (1), (2) and (3) (37) In a beta decay, element X, which has a half-life of 3 days, decays into a stable element Y. If the initial mass of X is 4 g, what will be the masses of X and Y after 6 days ? Mass of X Mass od Y A. B.

0g 1g

4g 3g

C. D. E.

2g 3g 4g

2g 1g 0g

(38) Two identical resistors R, an ammeter, a switch K and a cell are connected as shown.

R

A R K

When K is open, the ammeter reading is 1A. When K is closed, the reading will A. not change B. increase to 2A C. increase to 4A D. decrease to 0.5A E. decrease to 0.25A (39) Two heating coils A and B of resistance R and 2R respectively were connected to a battery as shown.

?

Coil A was immersed in an insulated calorimeter containing water, and the temperature of the water increased from 20°C to 70°C in 600s. Coil B was then immediately immersed in the same calorimeter. Boiling was first observed after a further A. 120s B. 180s C. 240s D. 360s E. 720s

(40) A radioactive nuclide AXZ undergoes radioactive decay inside a cloud chamber. The radiations emitted are subjected to a magnetic field and the resulting tracks are as shown in the figure below.

magnetic field acting out of the paper •

•

•

•

•

•

•

•

•

radioactive nuclide

What are the atomic number and mass number of the remaining nuclide ? Atomic no. Mass no. A. Z - 2 A-4 B. Z + 1 A-4 C. Z + 1 A D. Z - 1 A-4 E. Z - 1 A-2 (41) Which of the following statements concerning direct current (d.c.) and alternating current (a.c. is/are correct ? (1) The magnitude of voltage in d.c. is constant while that in a.c. varies. (2) The direction of electron flow in d.c. doese not c hange while that of a.c. reverses periodically. (3) Moving coil galvanometers can be used to measure d.c. but not a.c. A. (1) only D. (2) and (3) only

B. (3) only E. (1), (2) and (3)

C. (1) and (2) only

(42) What length of metal wire of cross-sectional area 2.5 x 10-7 m2 and resistivity 5.0 x 10-7 ohm-metre is required to make a heating coil rated at 12V, 24W ?

A. 2 m D. 6 m

B. 3 m E. 12 m

C. 4 m

(43) Which of the following can bring about a deflection of the electron beam in a cathode ray tube ? (1) Increasing the filament current (2) Increasing the potential difference between cathode and anode

(3) Decreasing the potential difference across the deflection plates A. (1) only B. (3) only C. (1) and (2) only D. (2) and (3) only E. (1), (2) and (3) (44) In the circuit below, V is a voltmeter of high internal resistance and A is an ammeter of low internal resistance. 2V

K V

A

100Ω

What is the voltmeter reading when (a) switch K is open , (b) switch K is closed ?

A. B. C. D. E.

K open 0V 0V 1V 2V 2V

K closed 0V 2V 1V 0V 2V

(45) Three coils A, B and C are wrapped around an iron core as shown. Coil A has N turns while coil B and C both have N/2 turns. V

A B

C

If an input voltage V is applied across A, what will be the voltage acting across coil C ? A. V/4 B. V/2 C. V D. 2V E. 4V