Physics Model Question Paper 13: (For Class 11 and 12 and Pre-Medical/Engineering Entrance)

1.

1 curie represents

(A) 1 disintegration per second

(B) 10⁶ disintegrations per second

(C) 3.7 ´ 10¹⁰ disintegrations per second

(D) 3.7 ´ 10⁷ disintegrations per second

Answer: (C)

2.

1.56 ´ 10⁵ J of heat is conducted through a 2 m² wall of 12 cm thick in one hour. Temperature difference between the two sides of the wall is 20°C. The thermal conductivity of the material of the wall is

(in W m^–1 K^–1)

(A) 0.11

(B) 0.13

(C) 0.15

(D) 1.2

Answer: (B)

3.

310 J of heat is required to raise the temperature of 2 moles of an ideal gas at constant pressure from 25°C to 35°C. The amount of heat required to raise the temperature of the gas through the same range at constant volume is

(A) 452J

(B) 276J

(C) 144J

(D) 384J

Answer: (C)

4.

A 1250 W heater operates at 115 V. What is the resistance of the heating coil?

(A) 1.6 W

(B) 13.5 W

(C) 1250 W

(D) 10.6 W

Answer: (D)

5.

A 20 cm length of a certain solution causes right handed rotation of 38°. A 30 cm length of another solution causes left handed rotation of 24°. The optical rotation caused by 30 cm length of a mixture of the above solutions in the volume ratio 1 : 2 is

(A) right handed rotation of 3°

(B) left handed rotation of 3°

(C) right handed rotation of 14°

(D) left handed rotation of 14°

Answer: (A)

6.

A and B are two metals with threshold frequencies 1.8 ´ 10¹⁴HZ and 2.2 ´ 10¹⁴Hz. Two identical photons of energy 0.825 eV each are incident on them. Then photoelectrons are emitted in

(A) A alone

(B) B alone

(C) in both A and B

(D) in neither A nor B

(Take h = 6.6 ´ 10^-34 Js)

Answer: (A)

7.

A balloon is rising vertically up with a velocity of 29ms^-1. A stone is dropped from it and it reaches the ground in 10 seconds. The height of the balloon when the stone was dropped from it is (g = 9.8 ms^-2)

(A) 100 m

(B) 200 m

(C) 400 in

(D) 150 m

Answer: (B)

8.

A body floats in water with 40% of its volume outside water. When the same body floats in an oil, 60% of its volume remains outside oil. The relative density of oil is

(A) 0.9

(B) 1.0

(C) 1.2

(D) 1.5

Answer: (D)

9.

A body is moving with velocity 30 m/s towards east. After 10 seconds its velocity becomes 40 m/s towards north. The average acceleration of the body is

(A) 5 m/s²

(B) 1 m/s²

(C) 7 m/s²

(D) 7 m/s²

Answer: (A)

10.

A body of mass 6 kg is acted upon by a force which causes a displacement in it given by x =  metre where t is the time in second.

The work done by the force in 2 seconds is

(A) 12 J

(B) 9J

(C) 6 J

(D) 3 J

Answer: (D)

11.

A box is moved along a straight line by a machine delivering constant power. The distance moved by the body in time t is proportional to

(A)

(B)

(C)

(D) t²

Answer: (C)

12.

A boy standing at the top of a tower of 20 m height drops a stone. Assuming g = 10 ms^–2, the velocity with which it hits the ground is

(A) 5.0 m/s

(B) 10.0 m/s

(C) 20.0 m/s

(D) 40.0 m/s

Answer: (C)

13.

A bullet moving with a speed of 100 ms^-1 can just penetrate two planks of equal thickness. Then, the number of such planks penetrated by the same bullet when the speed is doubled in will be _______.

(A) 4

(B) 8

(C) 6

(D) 10

Answer: (B)

14.

A Carnot engine has efficiency 25%. It operates between reservoirs of constant temperatures with temperature difference of 80°C. What is the temperature of the low-temperature reservoir?

(A) –25°C

(B) 25°C

(C) –33°C

(D) 33°C

Answer: (C)

15.

A Carnot's engine operates with source at 127°C and sinks at 27°C. If the source supplies 40 kJ of heat energy, the work done by the engine is

(A) 1 kJ

(B) 4 kJ

(C) 10 kJ

(D) 30 kJ

Answer: (C)