A bullet of mass 0.1 kg moving horizontally with speed 400 m s⁻¹ hits… | JEE Main 2023 (8 Apr, Shift 2)

Q4JEE Main 2023 · 8 APR · SHIFT 2Medium

Collisions

A bullet of mass $0.1\text{ kg}$ moving horizontally with speed $400\text{ m s}^{-1}$ hits a wooden block of mass $3.9\text{ kg}$ kept on a horizontal rough surface. The bullet gets embedded into the block and moves $20\text{ m}$ before coming to rest. The coefficient of friction between the block and the surface is __________. (Given $g = 10\text{ m/s}^2$ )

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Answer: (b)

Momentum: $0.1 \times 400 = 4\,v \Rightarrow v = 10\text{ m/s}$
Friction stops it: $v^2 = 2\mu g s \Rightarrow 100 = 2\mu(10)(20)$
$\mu = \frac{100}{400} = 0.25$
So the answer is (b) 0.25.

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Collisions question from JEE Main 2023 (8 Apr, Shift 2)

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