A body of mass 10 kg is moving with a velocity 20 m s^-1.

If the mass of the body is doubled and its velocity is halved,

find:

(i) the initial kinetic energy, and

(ii) the final kinetic energy.

Given,

Initial Mass = 10 kg and

Final mass = 2 × 10 kg = 20kg

Initial Velocity = 20 m / s

Changed velocity v2 = 20 / 2 = 10 m / s

(i) Initial kinetic energy = 1 / 2 × mass × (velocity)²

$\text {Initial Kinetic Energy} = \dfrac{1}{2} \times 10 \times (20)^2 \\[0.5em] \Rightarrow \text{Initial kinetic energy} = 2000J \\[0.5em]$

(ii) Final kinetic energy

$\text {Final Kinetic Energy} = \dfrac{1}{2} \times 20 \times (10)^2 \\[0.5em] \Rightarrow \text{Final kinetic energy} = 1000J \\[0.5em]$