A ball is dropped from a height of 10 m. If the energy of the ball reduces by 40% after striking the ground, how much high can the ball bounce back? (g = 10 m s^–2)

Height = 10m

Energy of the ball reduces by 40%

So, PE = m g h = m × 10 × 10 = 100m J.

Energy is reduced by 40% then the remaining energy is 100m – 40m = 60m J.

Now 60m = mx 10 x h’ ⇒ h’ = 6m