A ball is allowed to fall from a height of 10 m. If there is 40% loss of energy due to impact, then after one impact ball will go up to (in m)

mgh = initial potential energy
mgh' = final potential energy after rebound
As 40% energy lost during impact

 $\therefore$mgh'=60% of mgh 
$\Rightarrow \mathrm{h}\text{'}=\frac{60}{100}\times \mathrm{h}=\frac{60}{100}\times 10=6\mathrm{m}$