A ball is thrown vertically downwards from a height of 20 m with an initial velocity . It collides with the ground, loses 50 percent of its energy in collision and rebounds to the same height. The initial velocity is (Take g = )
The situation is shown in the figure
Let be the velocity of the ball with which it collides with ground. Then according to the law of conservation of energy,
Gain in kinetic energy = loss in potential energy
Now, when the ball collides with the ground, 50% of its energy is lost and it rebounds to the same height h.