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The slope of the kinetic energy versus position vector curve gives the rate of change of

1) Momentum 2) velocity 3) Force 4) Power Answer: 1) Momentum Solution: Slope = dK.E/dx = mv (dv/dx) = mv (dv/dt) x (dt/dx) = mv... View Article

The work done against gravity in taking 10 kg mass at 1m height in 1 sec will be

1) 49 J 2) 98 J 3) 196 J 4) None of these Answer: 2) 98 J Solution: Work done = mgh = 10 x 9.8 x 1 = 98 J... View Article

A force of 5N acts on a 15kg body initially at rest. The work done by the force during the first second of motion of the body is

1) 5J 2) (⅚) J 3) 6J 4) 75J Answer: 2) (⅚) J Solution: Force, F = ma 5 = 15a a = (1/3) m/s2 Since, S = ut + (1/2)at2 S = 0 + (1/2)... View Article

A man pushes a wall and fails to displace it. He does

1) Negative work 2) Positive but not maximum work 3) No work at all 4) Maximum work Answer: 3) No work at all Solution: Work = Force x... View Article

If the unit of force and length each be increased by four times, then the unit of energy is increased by

1) 16 times 2) 8 times 3) 2 times 4) 4 times Answer: 1) 16 times Work = Force x Displacement If the unit of force and length is increased by four... View Article

A body of mass 1 kg is thrown upwards with a velocity 20 m/s. It momentarily comes to rest after attaining a height of 18 m. How much energy is lost due to air friction (g = 10 m / s²)

1) 20 J 2) 30 J 3) 40 J 4) 10 J Answer: 1) 20 J Solution: The energy lost due to the air friction will be equal to the difference in... View Article

Assertion The apparent weight of a body in an elevator moving with some downward acceleration is less then the actual weight of body. Reason The part of the weight is spent in producing downward acceleration, when body is in elevator.

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

Assertion A reference frame attached to earth is an inertial frame of reference. Reason The reference frame which has zero acceleration is called a non-inertial frame of reference.

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

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