Question

A ball is dropped from a height of 10 metre is the energy of the ball reduces by 40% after strike the ground how much high the ball can bounce back?

Answer 1

Since, Height = 10 metres
Acceleration due to gravity = 10 m/s^2
Let the mass be m
Therefore, Potential energy = m x g x h = m x 10 x 10 = 100m
Since, Initial Potential energy is always equal to final kinetic energy
Therefore, maximum kinetic energy before bouncing= 100m
Kinetic energy is reduced by 40% due to friction after bouncing
= 100m - (40% of 100m)
= 100m - 40m
= 60m is the inital kinetic energy after the ball is bounced.
Since, Initial kinetic energy = Final potential energy
=> Final potential energy = 60m
=> 60m = m x g x h     (Mass being constant is cancelled out)
=> 60 = 10 x h
=> h= 6 metres. Ans