Question

A ball is dropped from a height of 10 m. If the energy of the ball reduces by 40% after striking the ground, how much high can the ball bounce back? $(g=10m{s}^{-2})$

Answer 1

Given,
h = 10m
$g=10m{s}^{-2}$
$E=W=mgh=m\times 10\times 10=100mJ$.
Energy is reduced by 40% then the remaining energy is 60 mJ.
Therefore, $60m=m\times 10\times h^{\prime }$ or $h^{\prime }=6m$