1979 Paper 2

Multiple-Choice questions 1979 (1) Two particles A and B of masses m and 2m respectively are projected vertically upward with the same initial velocity u. If air resistance can be neglected, which of the following statements is/are correct ? (1) A will reach a great height than B. (2) The energy required to project A upward is smaller than that required to project B. (3) Both will have the same potential energy when they reach their respective maximum height. A. (1) only B. (2) only C. (3) only D. (1) and (2) only E. (1) and (3) only (2) An object weighing 50 N is hung symmetrically from two hooks as shown.

50N

What is the downward force acting on each hook ? A. 12.5 N B. 25 N C. 50 N D. 100 N E. 200 N (3) Three forces F1, F2 and F3 acting in the same place at a point O are represented in magnitude and direction by the diagram below. F1

F3 F2

To balance these forces, a single force F is applied. F should be equal to A. F1 D. F1 + F2

B. F2 E. 2F2

C. F3

(4) Two objects of weights 5N and 10 N are suspended from the ceiling as shown in the diagram below.

T

1

3N T

2

10N

What will be the tensions T1 and T2 ?

A. B. C. D. E.

T1 5N 5N 15 N 15 N 15 N

T2 5N 10 N 5N 15 N 10 N

(5) X, Y and Z are three weights suspended in equilibrium as shown in the below diagram inside a lift. As the lift is uniformly accelerated upwards, the angle i will A. increase B. decrease C. remain the same D. increase at first and decrease later E. decrease at first and increase later

θ

X

.

Z Y

(6) An object is projected vertically upward. A, X, Y and Z are the points on the path of its flight as shown in the diagram. At which of the points X, Y and Z does the object have the same total energy as it possesses at A, assuming that air resistance can be neglected?

X Y

A

Z 8

A. at Y only B. at X and Y only C. at X and Z only D. at X, Y and Z E. at none of the points X, Y or Z (7) An object is given a push so that it leaves the surface of a horizontal table with a velocity v. Which of the following graphs correctly represents the change of kinetic and potential energy during the flight of the object ?

A

B

KE

C

KE

D

KE

PE

E

KE

PE

PE

KE

PE

PE

(8) The graph below represents the variation of velocity with time of a particle moving in a straight line.

velocity/ m/s 20

Time/s 5

20

Which of the following statements is/are correct ? (1) There is an unbalanced force acting on the particle interval. (2) The particle is uniformly accelerated in the first five seconds. (3) The total displacement of the particle is 600 m. A. (1) only B. (2) only C. (3) only D. (1) and (2) only E. (1), (2) and (3)

during the 5 - 20 seconds

(10) A bomb is dropped from a jet bomber cruising horizontally at constant velocity. Which of the following correctly represents the path of the bomb as seen by (1)the pilot in another plane X travelling at the same velocity. (2) a stationary observer on the ground to the right of the bomber ? (1) Pilot in X

A

B

C

D

E

(2) Stationary observer

(11) Which of the following is the correct order of magnitude in metres for the wavelengths of (1) infra-red rays, (2) radio waves and (3) gamma rays ? 102m A. B. C. D. E.

(1) (3) (3) (2) (2)

10-5m (2) (2) (1) (1) (3)

10-13m (3) (1) (2) (3) (1)

(12) An inexpansible vessel contains 1.2 kg gas at 300 K. What is the mass of gas expelled from the vessel if it is heated from 300 K to 400 K under constant pressure ? A. 0.2 kg B. 0.3 kg C. 0.6 kg D. 0.75 kg E. 0.9 kg (13) A definite mass of a certain vapour was colled and the cooling curve for the process is shown below.

Temperature

Time/min 5 10 18 22

Which of the following statement/s concerning the process is/are correct ? (1) Vapour and liquid were in equilibrium in the 9th minute of the process. (2) No heat was given out to the surroundings in the 20th minute.

(3) All the liquid completely changed into solid in the 20th minute. A. (1) only B. (3) only C. (1) and (2) only D. (2) and (3) only E. (1), (2) and (3) (15) A fixed mass of gas is trapped inside a cylinder by an air tight and frictionless position under the action of a constant force as shown in the diagrtam below.

Which of the following assertions is/are correct of the temperature of the gas is gradually lowered ? (1) The pressure of the gas decreases (2) The volume of the gas decreases (3) The average velocity of the gas molecules decreases. A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only E. (1), (2) and (3) (16) The diagram below shows how a ray of light from an object O enters the eye of an observer after three sucessive reflections by the parallel mirrors M and N. The distance of the image from mirror M as seen by the observer is M 2cm O 1cm N

A. 2 cm

B. 4 cm C. 5 cm D. 6 cm E. 8 cm (17) A real image I of an object O is formed by a convex lens L as shown below. A concave lens L1 is placed between L and I such that a real image I' is obtained.

Which of the following statements concerning I' is/are correct ? (1) I' is also an inverted image (2) I' is larger than I (3) I' is further away from L than I A. (1) only B. (2) only C. (1) and (2) only D. (2) and (3) only E. (1), (2) and (3)

(18) The graph below shows how the air pressure of the ear-drum of time when a sound wave is heard.

What is the frequency of the wave ? A. 125 Hz B. 250 Hz

a listener varies with

C. 500 Hz D. 1 k Hz E. 2 k Hz (19) The diagram below shows a gold leaf electroscope with a diverging gold leaf.

Which of the following will increase the divergence of the gold leaf ? (1) Bringing a positively charged rod near the cap (2) Bringing a neddle-like conductor near the cap (3) Disconnecting the case from earth A. (1) only B. (2) only C. (1) and (2) only D. (1) and (3) only E. (1), (2) and (3) (20) A radioactive isotope will undergo a change in its atomic number by emission of (1) alpha particles (2) beta particles (3) gamma rays Which of the above assertion is/are correct ? A. (1) only B. (2) only C. (1) and (2) only D. (2) and (3) only E. (1), (2) and (3) (21) Which of the follwoing is the correct arrangement for the conversion of a galvanometer into an ammeter ? A

High resistance

B

Low resistance

G

G

C

D

G

High resistance

G

Low resistance

Low resistance

E

G

High resistance

(22) Which of the following will decrease the electrical resistance of a metal wire ? (1) Lowering in temperature (2) Reducing its length (3) Reducing its cross-sectional area A. (1) only B. (2) only C. (3) only D. (1) and (2) only E. (1) and (3) only (23) Water is heated by electric heaters in a well-lagged calorimeter as shown below.

A B V

V

The rate of rise in the temperature of water when the switch is connected to A is Ha but when the switch is connected to B, the rate is Hb. What is the ratio of Ha to Hb ? A. 1 : 4 B. 1 : 2 C. 1 : 1 D. 2 : 1 E. 4 : 1 (24) The images formed by a single concave lens are always A. real and inverted B. real and erect C. virtual and inverted D. virtual and erect E. larger than the object (30) Which of the following would be increased by reducing the friction between the string and the pulleys of a block and tackle system ? (1) The mechanical advantage of the syatem (2) The velocity ratio of the system (3) The efficiency of the system A. (1) only B. (2) only C. (1) and (2) only D. (1) and (3) only E. (1), (2) and (3) (31) When the bob of a simple pendulum is displaced from its rest position and is then released as shown, it will

A. move with constant velocity B. move with constant acceleration C. move with a periodic motion D. acquire constant momentum E. acquire constant kinetic energy (32) A note of frequency f has a velocity v and a wavelength d in air. What will be the wavelength and velocity of another note of frequency 2f ?

A. B. C. D. E.

Wavelength Velocity d/2 v d/2 2v d 2v 2d v 2d 2v

(33) Three resistors of resistances R, R and 2R ohms are connected as shown in the circuit below. R A

B

2R

C

R

If the potential difference across BC is 6 V, what will be the potential difference across AB ? A. 12 V B. 6 V C. 3 V D. 2 V E. 1.5 V

(34) A current of I amperes is flowing in the circuit shown below.

R *

* A

B

If the p.d. across the terminals of the cells is V volts and the resistance of AB is R ohms, the power dissipated in the resistor AB will be A. V2/R watts B. I2R watts C. IR watts D. VI watts E. VI2 watts (35) The acceleration voltage in a cathode ray tube is V volts. The kinetic energy acquired by an electron of mass m kg and charge C coulombs in the beam is A. CV joules B. CV/2 joules C. mCV joules D. mV2 joules E. mV2/2 joules (36) Which of the following will affect the secondary e.m.f. of a transformer ? (1) Replacing the laminated iron core with a solid iron core (2) Reducing the number of turns in the primary coil (3) Reversing the terminals of the a.c. primary source A. (1) only D. (2) and (3) only

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

C. (1) and (2) only

(37) The upper and lower fixed points of the temperature scale are chosen to be the steam point and ice point at normal atmospheric pressure. The reasons are (1) these two temperatures can be easily obtained experimentally (2) the expansion of substances varies uniformly between these temperatures (3) a chnage in atmosphreic pressure does not affect these temperatures Which of the above statements is/are correct ? A. (1) only B. (2) only D. (1) and (3) only E. (2) and (3) only

C. (1) and (2) only

(38) 45x-90x-45x triangular prisms are used as reflecting prisms in a binocular. The refractive index of the prisms can be (1) 1.25 (2) 1.50 (3) 1.70 Which of the above assertions is/are correct ? A. (1) only B. (2) only C. (1) and (2) only D. (2) and (3) only E. (1), (2) and (3)

(39) A positively charged plastic bead is falling under gravity between two strong magnetic poles as hown below.

+

N

S

The action of the magnetic field will A. increase the vertical acceleration of the bead B. cause the bead to deflect in a direction out of the page C. cause the bead to deflect towards the N pole D. cause the bead to deflect towards the S pole E. have no effect on the motion of the bead (40) A closed U-tubed is filled with water and oil as shown in the diagram below.

If the atmospheric pressure is P, the acceleration due to gravity is g and the densities of oil and water are respectively d1 and d2 , the pressure at the point C inside the closed end of the U-tube will be A. h1d1g B. (h1 + h2) d1g C. P + h1d1g D. P + h2d2g E. P + (d1 - d2)h1g

(42) Three identical cells are arranged differently as shown below. X

Y

Z

Which of the above arrangements X, Y and Z has (1) the highest e.m.f., (2) the smallest equivalent internal resistance ? (1) Highest e.m.f. A. B. C. D. E.

X X Y Y Z

(2) Smallest internal resistance Y Z X Z Y

(43) This problem refers to the oil-film experiment. Let one, two fall into the tray, which of the follwoing statements is/are correct ? (1) The film is probably of uniform thickness in each case (2) The film must be one molecule thick (3) Each molecule of the oleic acid is a cube A. (1) only B. (1) and (2) only C. (1) and (3) only D. (2) and (3) only E. (1), (2) and (3)

and three drops of oleic acid