JEE Main · 2023 · 08 Apr 2023 · Shift 2 · Work, Power & Energy

A body of mass 5 kg is moving with a momentum of

10 kg ms^{- 1}

. Now a force of 2 N acts on the body in the direction of its motion for 5 s. The increase in the Kinetic energy of the body is

____

Answer: 30

Solution

The impulse of the applied force changes the momentum:

p_{f} = p_{i} + F Δ t = 10 + (2) (5) = 20 kg m s^{- 1}

. Writing the kinetic energy as

K = \frac{p ^{2}}{2 m}

, the increase is

Δ K = \frac{p _{f}^{2} - p _{i}^{2}}{2 m} = \frac{2 0 ^{2} - 1 0 ^{2}}{2 ( 5 )} = \frac{400 - 100}{10}

. The increase in the kinetic energy of the body is

30 J

JEE Main · 2023 · 08 Apr 2023 · Shift 2 · Integer answer

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