Question

A ball is dropped from a height of 10 m if 40% of its energy is lost on collision with the earth the. After collision the ball will rebound to a height of

Answer 1

The initial energy of a ball is

$$E_1=mgh_1$$

The final energy of a ball is

$$E_2=mgh_2=0.6E_1=0.6mgh_1$$

Hence, the ball will rebound to a height of

$$h_2=0.6h_1=0.6*10\:\rm m=6\:\rm m$$