Q19Short answer
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)
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m g h = m ×10 ×10 = 100m J. Energy is reduced by 40% then the remaining energy is 60m J. Therefore, 60 m = m ×10× h′ or h′ = 6 m OPNN