JEE Main · 2024 · 04 Apr 2024 · Shift 1 · Work, Power & Energy

If a rubber ball falls from a height h and rebounds upto the height of

h /2

. The percentage loss of total energy of the initial system as well as velocity ball before it strikes the ground, respectively, are :

(A) $50%, \frac{gh}{2}$
(B) $50%, gh$
(C) $40%, 2 gh$
(D) $50%, 2 gh$ ✓ Correct

Answer: (D)

Solution

Velocity just before striking the ground (fall from

h

v = 2 g h .

Rebounds to

h /2

, so mechanical energy after impact is

m g (h /2)

Fractional energy loss = \frac{m g h - m g ( h /2 )}{m g h} = \frac{1}{2} = 50%.

So the loss is

50%

and the speed before impact is

2 g h

. Option D.

JEE Main · 2024 · 04 Apr 2024 · Shift 1 · Single correct option

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