JEE Main · 2022 · 28 Jul 2022 · Shift 2 · Work, Power & Energy

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A bullet of mass 200 g having initial kinetic energy 90 J is shot inside a long swimming pool as shown in the figure. If it's kinetic energy reduces to 40 J within 1s, the minimum length of the pool, the bullet has a to travel so that it completely comes to rest is

(A)45 m✓ Correct
(B)90 m
(C)125 m
(D)25 m

Answer: (A)

Solution

From kinetic energy, initial velocity

u = 2 K_{i} / m = 2 \times 90/0.2 = 30

m/s. Final velocity after 1 s:

v = 2 \times 40/0.2 = 20

m/s. Acceleration

a = (v - u) / t = (20 - 30) /1 = - 10

m/s². Distance to stop:

s = - u^{2} / (2 a) = - 900/ (- 20) = 45

JEE Main · 2022 · 28 Jul 2022 · Shift 2 · Single correct option

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