A bullet of mass 50 g is fired with a speed $100 \mathrm{~m} / \mathrm{s}$ on a plywood and emerges with $40 \mathrm{~m} / \mathrm{s}$. The percentage loss of kinetic energy is :

JEE Main · 2024 · 06 Apr 2024 · Shift 1 · Work, Power & Energy

A bullet of mass 50 g is fired with a speed

100 m / s

on a plywood and emerges with

40 m / s

. The percentage loss of kinetic energy is :

(A) $32%$
(B) $44%$
(C) $16%$
(D) $84%$ ✓ Correct

Answer: (D)

Solution

K_{i} = \frac{1}{2} m (100)^{2}

K_{f} = \frac{1}{2} m (40)^{2}

% loss = \frac{K _{i} - K _{f}}{K _{i}} \times 100 = \frac{10 0 ^{2} - 4 0 ^{2}}{10 0 ^{2}} \times 100 = \frac{10000 - 1600}{10000} \times 100 = 84%.

JEE Main · 2024 · 06 Apr 2024 · Shift 1 · Single correct option

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