Question

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

Answer 1

Given : Initial velocity $u=5$ $m/s$

Final velocity $v=2$ $m/s$

The work done is equal to the change in the kinetic energy of an object.

$W=\frac{1}{2}m(v^2-u^2)$

$W=\frac{1}{2}\times 20\times (2^2-5^2)$

$⟹W=-210$ $J$