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Assertion The slope of momentum versus time curve gives us the acceleration. Reason Acceleration is given by the rate of change of momentum.

1) If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion. 2) If both Assertion and Reason are true... View Article

A closed compartment containing gas is moving with some acceleration in the horizontal direction. Neglect effect of gravity. Then the pressure in the compartment is

1) Same everywhere 2) Lower in front side 3) Lower in the rear side 4) Lower in the upper side Answer: 2) Lower in front side Solution:... View Article

A uniform metal chain is placed on a rough table such that one end of the chain hangs down over the edge of the table. When one-third of its length hangs over the edge, the chain starts sliding. Then, the coefficient of static friction is

1) 3/4 2) 1/4 3) 2/3 4) 1/2 Answer: 4) 1/2 Solution: Length of the chain = l Mass of the chain = m one-third of its length hangs... View Article

A body of mass 2 kg moving with a velocity of 3 ms^-1 collides head-on with a body of mass 1 kg moving in the opposite direction with a velocity of 4 ms^-1. After the collision, two bodies stick together and move with a common velocity which in ms ^-1 is equal to

1) 1/4 2) 1/3 3) 2/3 4) ¾ Answer: 3) 2/3 Applying law of conservation of momentum m1v1 - m2v2 = (m1 + m2)v ⇒ (2 x 3) - (1 x 4)... View Article

In a head-on elastic collision of a very heavy body moving at v with a light body at rest, the velocity of the heavy body after the collision is

1) v 2) 2v 3) zero 4) v/2 Answer: 1) v Solution: In an elastic collision, the magnitude of the velocity will remain the same but... View Article

A 10 kg object collides with a stationary 5 kg object and after the collision, they stick together and move forward with velocity 4 ms^-1. What is the velocity with which the 10 kg object hit the second one?

1) 4 ms-1 2) 6 ms-1 3) 10 ms-1 4) 12 ms-1 Answer: 2) 6 ms-1 Solution: m1u1 + m2u2 = (m1 + m2)v 10 x u1 + 5 x 0 = (10 + 5) x... View Article

A man does a given amount of work in 10 s. Another man does the same amount of work in 20 s. The ratio of the output power of the first man to the second man is

1) 1 2) 1/2 3) 2/1 4) None of these Answer: 3) 2/1 Solution: Power = Work/time P ∝ 1/t P1/P2 = t2/t1 = 20/10 = 2/1... View Article

The machine gun fires 240 bullets per minute. If the mass of each bullet is 10 g and the velocity of the bullets is 600 ms^-1 , the power (in kW) of the gun is

1) 43200 2) 432 3) 72 4) 7.2 Answer: 4) 7.2 Solution: Power = Work done/Time taken = Total kinetic energy of the bullets/Time... View Article

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

1) t1/2 2) t3/4 3) t3/2 4) t2 Answer: 3) t3/2 Solution: Let S be the distance moved by the body Power, P = F.v Force, F = m.a... View Article

A steel ball of mass 5 g is thrown downward with a velocity of 10 ms^-1 from a height of 19.5 m and it penetrates sand by 50 cm. The change in mechanical energy will be (take, g =10ms^-2 )

1) 1 J 2) 1.25 J 3) 1.5 J 4) 1.75 J Answer: 2) 1.25 J Solution: Mass, m = 5g = 0.005 Kg h = 19.5 m x = 50 cm = 0.5 m v = 10 m/s... View Article

A ball of mass 2 kg moving with velocity 3 ms^-1, collides with spring of natural length 2m and force constant 144 Nm^-1. What will be the length of the compressed spring?

1) 2 m 2) 1.5 m 3) 1 m 4) 0.5 m Answer: 2) 1.5 m Solution: The kinetic energy of the ball = Potential energy of the spring (1/2)mv2 =... View Article

Two springs of spring constants 1500 Nm^-1 and 3000 Nm^-1 respectively are stretched with the same force. They will have potential energy in the ratio

1) 1 : 2 2) 2 : 1 3) 1 : 4 4) 4 : 1 Answer: 2) 2 : 1 Solution: Potential Energy, U = (1/2)kx2 --------(1) Force ∝... View Article

The kinetic energy of a body becomes four times its initial value. The new momentum will be

1) same as the initial value 2) twice the initial value 3) thrice the initial value 4) half of its initial value Answer: 2) twice the... View Article

A spherical ball of mass 20 kg is stationary at the top of a hill of height 100 m. It rolls down a smooth surface to the ground, then climbs up another hill of height 30 m and height of 20 m above the ground. The velocity attained by the ball is

1) 40 ms-1 2) 20 ms-1 3) 10 ms-1 4) 10√30 ms-1 Answer: 1) 40 ms-1 Solution: A spherical ball of mass 20 kg is stationary at the top of a... View Article

A bomb of mass 3.0 kg explodes in the air into two pieces of masses 2.0 kg and 1.0 kg. The smaller mass goes at a speed of 80 ms^-1. The total energy imparted to the two fragments is

1) 1.07 kJ 2) 2.14 kJ 3) 2.4 kJ 4) 4.8 kJ Answer: 4) 4.8 kJ Solution: From law of conservation of momentum mv = m1v1 + m2v2 3 x 0 =... View Article

A bomb of mass 9 kg explodes into two parts. One part of mass 3 kg moves with velocity 16 m/s, then the kinetic energy of the other part is

1) 162 J 2) 150 J 3) 192 J 4) 200 J Answer: 3) 192 J Solution: Given, Mass of the bomb = 9 Kg Mass of smaller part = 3 kg Mass of... View Article

A spring gun of spring constant 90 Ncm^-1 is compressed 12 cm by a ball of mass 16 g. If the trigger is pulled, the velocity of the ball is

1) 50 ms-1 2) 9 ms-1 3) 40 ms-1 4) 60 ms-1 5) 90 ms-1 Answer: 5) 90 ms-1 Potential energy stored in the spring= kinetic energy of the... View Article

A river of salty water is flowing with a velocity of 2 ms^-1. If the density of the water is 1.2 g/cc, then the kinetic energy of each cubic metre of water is

1) 2.4 J 2) 24 J 3) 2.4 kJ 4) 4.8 kJ Answer: 3) 2.4 kJ Solution: Given, The velocity of water, v = 2 m/s Density of... View Article

A 16 kg block moving on a frictionless horizontal surface with a velocity of 4 m/s compresses an ideal spring and comes to rest. If the force constant of the spring be 100 N/m, then the spring is compressed by

1) 1.6 m 2) 4 m 3) 6.1 m 4) 3.2 m Answer: 1) 1.6 m Solution: Kinetic energy of the block, K = (1/2)mv2 The kinetic energy will be... View Article

If the kinetic energy of a body is increased two times, its momentum will

1) half 2) remain unchanged 3) be doubled 4) Increases √2 times Answer: 4) Increases √2 times Solution: K =... View Article

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