1985 Physics Paper2

Multiple-Choice Question 1985 Take g = 10 m/s2. All cells are assumed to have negigible internal resistance. [1] The graph below shows the variation of the velocity of a car with time. velocity/ms-1

6 4 2

time/s 0 1 2 3

What is the acceleration of the car ? A. 0.5 m/s2 B. 1.5 m/s2 D. 4.0 m/s2 E. 6.0 m/s2

C. 2.0 m/s2

[2] A car moving with speed 50 km/h can be stopped in a distance of 15 m. In what distance can the car be stopped when its speed is 70 km/h under the same conditions ? A. 7.7 m B. 10.9 m C. 17.7 m D. 21.0 m E. 29.4 m [3] What physical quantity does the area of the shaded portion of each of the above graphs represent ? speed

force

time

0 I

distance

0 II

A. B. C. D. E.

I acceleration distance acceleration distance force

II energy power change of momentum energy power

[4] A ball of mass 2 kg drops from rest to the ground from a height 5 m and rebounds to the same height. If the same duration of the impact between the ball and the ground is 2.0 seconds, what is the total reaction of the ground on the ball ? A. 20 N B. 100 N C. 200 N D. 220 N E. 420 N [5] A windmill can produce electric energy at the rate of 20 kW when the wind speed is 10 m/s. If the efficiency is 50 %, what force, in 103 N, is exerted by the wind on the windmill ? A. 2 B. 4 C. 6 D. 8 E. 10 [6]

An object is projected vertically upwards. Which of the following graphs correctly describes the variation of the kinetic energy E of the object with height h ?

A

E

B

0

D A

h

E

0

E

EE E

0

C D

h

h

E

0

h

E

0

h

[7] Two blocks A and B of masses 1 kg and 1.5 kg respectively are resting on a smooth horizontal surface and are linked by a string. They are pulled by a force of 10 N as shown in the diagram below. 10N

T1

T2

A

B

What will the tensions T1 and T2 be ?

A. B. C. D. E.

Tension T1 10 N 10 N 10 N 6N 4N

Tension T2 10 N 6N 4N 4N 6N

[8] A block is moving with uniform velocity along a rough horizontal plane. Which of the following statements is/are true ? (1) The kinetic energy of the block is increasing. (2) The potential energy of the block is increasing. (3) The resultant force acting on the block is zero. A. (1) only D. (2) and (3) only

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

C. (1) and (2) only

[9] A diver jumps from a high platform into water at the point B as shown. A

B

C

The diver descends to C and then floats up to the water surface. Assume that the potential energy at point B is taken to be zero. Which of the following statements is/are true ?

At point C,

(1) the kinetic energy of the diver is at a maximum. (2) the kinetic energy of the diver is at a minimum. (3) the sum of the kinetic energy and potential energy of the A. (1) only D. (1) and (3) only

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

diver is zero.

C. (3) only

[10] A block is given an initial velocity up a smooth inclined plane. Which graph below shows the acceleration of the block against time ?

(The upward direction of motion along the plane is taken as positive.) A

a

B

a

t 0

a

E

t 0

a

t 0

a

t

0

D

C

t 0

[11] With an increase in pressure, which of the follwoing effects is/are true ? (1) The melting point of ice will be increased. (2) The boiling point of water will be increased. (3) The rate of evaporation of water will be increased. A. (1) only D. (1) and (3) only

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

C. (3) only

[12] The initial pressure of a fixed mass of gas at 25°C is 2 x 105 Pa. What would its pressure be if the gas were reduced to half its original volume and its temperature were increased to 95°C ?

A. 123 k Pa D. 1520 k Pa

B. 324 k Pa E. 1980 k Pa

C. 494 k Pa

[13] Heat is needed to keep water boiling because energy is required to (1) overcome the effect of atmospheric pressure. (2) increase the kinetic energy of the water molecules. (3) increase the potential energy of the water molecules. A. (1) only D. (2) and (3) only

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

C. (1) and (3) only

[14] The difference in water temperature between the top and the bottom of a waterfall is 0.15°C. Assuming no heat is lost from the water to the surroundings, what is the height of the waterfall ? (The specific heat capacity of water is 4200 J/kg/K) A. 3.6 m D. 360 m

B. 28 m E. 540 m

C. 63 m

[15] A mountain climber finds that the boiling point of water at high altitudes is lower than that at sea level. To raise the boiling point, he could (1) use a pot with special tight-fitting lid. (2) increase the rate at which heat is supplied. (3) use a copper pot instead of a clay pot. A. (1) only D. (1) and (3) only

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

C. (1) and (2) only

[16] Which of the following statements correctly describes a concave lens ? (1) The image of a real object formed by the lens may be real or virtual depending on the object distance. (2) The image of an object formed by the lens may be magnified or diminished depending on the object distance. (3) It is used for the correction of short-sightedness. A. (1) only D. (2) and (30 only

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

C. (1) and (2) only

[17] In the figure below, the image I of an object placed at O is produced by a single lens. If the magnification is 2, what kind of lens has been used and where must it have been placed ?

A B O

C D

E

I

A. a concave lens placed at A B. a concave lens placed at B C. a convex lens placed at C D. a convex lens placed at D E. a convex lens placed at E [18] IN the diagram below, a light ray passes from medium Y to medium X and emerges to medium Y again. II Y

III

IV

I V

X

Y

The refractive index of medium X is smaller than that of medium Y. Which of the following represents the path of the emergent ray ? A. I D. IV

B. II

C. III E. V

[19] A fish in a tank of water looks through a thin glass wall X at a pin. The image of the pin observed by the fish will be X

pin

A. longer than it actually is and nearer to X B. longer than it actually is and further away from X C. of the same size as the object and at the same distance from X D. shorter than it5 actually is and nearer to X E. shorter than it actually is and further away from X [20] When an object of height 10 mm is placed in front of a mirror, the image formed is erect and of height 2 mm. Which of the following statements is/are true ? (1) The mirroe must be a concave mirror. (2) The image must be real. (3) If the object is moved nearer to the mirror, the image will still be erect. A. (1) only D. (2) and (3) only

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

C. (1) and (2) only

[21] Which of the following are longitudinal waves ? (1) sound waves transmitted through a solid (2) sound waves transmitted through water (3) waves in a vibrating string A. (1) only D. (1) and (3) only

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

C. (1) and (2) only

[22] When light travels from air to glass, which of the following statements is/are true ? (1) The speed of the light changes. (2) The wavelength of the light increases. (3) The frequency of the light remains unchanged. A. (1) only D. (2) and (3) only

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

C. (1) and (3) only

[23] A short pulse of microwaves travelling at 3 x 108 m/s was used to detect the position of a stationary weather balloon. It was found that the microwaves reflected from the balloon

were picked up 2 x 10-4 s after the pulse had been emitted from the station. The distance of the balloon from the station was A. 15 km B. 30 km C. 60 km 12 12 D. 1.5 x 10 m E. 3.0 x 10 m [24] Which of the following is in the correct order of increasing wavelengths ? A. infra-red rays, X-rays, radio waves B. infra-red rays, radio waves, X-rays C. X-rays, radio waves, infra-red rays D. X-rays, infra-red rays, radio waves E. radio waves, X-rays, infra-red rays [25] A stationary wave is produced in a string by a vertical vibrator as shown in the figure below. P A

vibrator

wall

If P is at the crest of an antinode at a certain instant, what is the direction of motion of the point A at that instant ? A. upwards B. downwards C. to the right D. to the left E. momentarily at rest

[33] Two uncharged metal spheres are suspended by insulating threads as shown in the diagram below. A plastic sheet is put between them.

+ + +

When a positively charged rod X is brought near them as shown, which of the following diagrams shows the resulting charge distribution on the spheres ?

A

B

C

-

+ + +

-

+++-

+++-

E D

- +

+ - + - +

+ + -

-

-

[34] An immersion heater A takes 10 minutes to boil a kettle of water while another immersion heater B takes 40 minutes to boil the same kettle of water under the same voltage supply. If the resistance of heater A is 100 ohms, what is the resistance of heater B? A. 25 ohms B. 50 ohms C. 100 ohms D. 200 ohms E. 400 ohms

[35] A student, who wishes to find the resistance of a light bulb when connected to a certain battery, incorrectly connects a voltmeter and an ammeter as shown in the diagram below.

A

V

What would be the most probable outcome of has error ? A. The voltmeter would burn out B. The ammeter would burn out C. The light bulb would burn out D. Both the ammeter and the voltmeter would burn out E. The voltmeter would indicate zer voltage [36] In the circuit below, all bulbs B are identical.

B

A1 B

B

B

A2

If ammeter A1 reads 1.8 A, what does ammeter A2 read ? A. 1.2 A D. 0.3 A

B. 0.9 A E. 0.1 A

C. 0.6 A

[37] Electric bulbs R are of rating 40W, 200V and electric bulbs S are of rating 60W, 200V. Which of the following combinations would produce the maximum brightness if connected to the same voltage ? R A

B

R

R

R

S C

D C

S

S

R E

S

[38] In the circuit below, when K1 is closed the voltmeter reads 12V.

24V

K1

6Ω

K2

6Ω

V

What would the reading be if both K1 and K2 are closed ? A. 8 V B. 12 V C. 16 V D. 18 V E. 24 V

S

[39] The 300 V generator in the diagram below is supplying electrical power to operate a piece of machinery which has a rating of 10 kW at 200 V. transmission cables

300V

generator

200V 10kW

machinery

The total resistance of the transmission cables is 2 ohms. What is the power loss in the transmission system ? A. 2.5 kW B. 5 kW D. 20 kW E. 4 kW

C. 10 kW

[40] Which of the two bulbs L1 and L2 in the circuit below will light up when the switch S is (1) opened ? (2) closed ?

a.c. power supply

S L1

L2

(1) When the switch S is open

A. B. C. D. E.

only L2 will light up only L2 will light up only L1 will light up only L1 will light up L1 and L2 will light up

(2) When the switch S is closed

only L1 will light up L1 and L2 will light up only L2 will light up L1 anf L2 will light up only L2 will light up

[41] The diagram below shows a transformer with the primary coil connected to an a.c. voltage of 200 V while the secondary coil is connected to a resistor of 100 ohms.

200V a.c. supply

100Ω

If there are 100 turns in the primary coil and 10 turns in the secondary coil, what is the current passing through the resistor ? (You may assume the efficiency of the transformer is 100 % .) A. 0.05 A D. 1 A

B. 0.1 A E. 20 A

C. 0.2 A

[42] A copper rod AB is free to move on two parallel conducting wires. It is pulled by a force F in the direction shown in the figure below. +D + + + A + + + + + + + + + +++ + + + + + + + + +++ + + + + + +P + + + Q + +F + + + + + + + +++ + + + + + + + + +++ + + + + + +C + + + B + + + + + +

The direction of the magnetic field is going into the paper. Which of the following statements is/are correct ? (1) A current will flow from C to D through P. (2) A current will flow from B to A through Q. (3) An e.m.f. will be set up across AB. A. (1) only D. (1) and (3) only

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

C. (3) only

[43] During radioactive decay, 90X230 becomes 90Y226. Which of the following statements would be correct ? (1) The change would involve alpha decay only. (2) One alpha particle and two beta particles would be

emitted.

(3) X and Y are two isotopes of the same element. A. (1) only D. (2) and (3) only

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

C. (1) and (3) only

[44] Which of the following will increase the resistance of a metal wire ? (1) increasing the length of the wire. (2) increasing the cross-sectional area of the wire. (3) increasing the temperature of the wire. A. (1) only D. (2) and (3) only

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

C. (1) and (3) only

[45] The radioactivity of a sample of material was measured on the first day of each month. The readings on July 1 and September 1 are 0.8 and 0.2 counts per second respectively. What is the half-life of the radioactive material ? A. 7 days B. 16 days C. 31 days D. 46 days E. 61 days End of file MC1985