Question

A ball is dropped from a height of 5 m and it rebounds back up to the height of 3m
Calculate its,
(a) KE when it strikes the ground.
(b) KE when it leaves the ground for rebounding.​

Answer 1

Initial kinetic energy =mgh, according to conservation of mechanical energy.

Final kinetic energy ,similarly ,is mg h'.

Change in kinetic energy =mg(h-h').

Percentage change in kinetic energy =[mg(h-h')/mgh]100=( 7.5/10)(100)=75%.