Question

A ball at rest is dropped from a height of $12m$. It looses $25$% of its kinetic energy on striking the ground and bounces back to a height $h$. Then value of $h$ is:

• A. $3m$
• B. $6m$
• C. $9m$
• D. $12m$

Answer 1

Answer: (C)

$9m$

The kinetic energy on reaching the ground will be equal to the initial potential energy, i.e. $KE=mg\left(12\right)$. Since the remaining kinetic energy (after loss) will be used to rise the block to height h,

$mg\left(12\right)(1-0.25)=mgh$

Hence, $h=9m$