Question

A ball is dropped from rest at a height of 60m .on striking the ground it loses 25% of its energy .to what height does it rebound

Answer 1

By energy conservation we can write

Total initial energy - Energy loss due to collision = Final total energy

Now to find the initial total energy we can write

$E_i = mgh_i$

here given that

$h_i = 60 m$

now initial total energy is given as

$E_i = m*g*60[\tex]</p><p>now 25% of this energy is lost due to collision</p><p>so the energy loss is given by</p><p>[tex]E_{lost} = 0.25 * m*g*60$

$E_{lost} = 15*m*g$

now by above equation

$E_i - E_{lost} = E_{final}$

$60*mg - 15*mg = E_{final}$

$E_{final} = 45*mg$

now final height is given as

$mgh_f = E_{final}$

now by above equation we can say

$mgh_f = 45*mg$

$h_f = 45 m$

so the ball will rebound to final height 45 m after collision.