Question

If the speed of a body is halved, what will be the change in its kinetic energy?

Answer 1

Kinetic energy of the body $K.E=\frac{1}{2}m{v}^2$

So, $K.E\propto v^2$

If speed of the body is halved, its kinetic energy will be reduced by a factor of $4$.

That is

$NewK.E=\frac{1}{2}m(\frac{v}{2}{)}^2$ = $\frac{K.E}{4}$