Q19 of 28 Page 69

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


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