Question

Certain force acting on a $20$ $kg$ mass changes its velocity from $5$ $m s^{–1}$ to $2$ $m s^{–1}$. Calculate the work done by the force.

Answer 1

Work done by the force = change in kinetic energy
= $\frac{1 }{ 2} \times m (v^2_1 - v^2_2)$

= $\frac{1 }{ 2} \times 20 \times (5^2 - 2^2)$
= $10 \times (25 - 4)$
= $10 \times 21$
= $210$ $J$.