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JEE Main 2019 (10 Apr, Shift 2) · Inertia, First & Second Laws

Inertia, First & Second Laws question from JEE Main 2019 (10 Apr, Shift 2)

Q30JEE Main 2019 · 10 APR · SHIFT 2Medium

Inertia, First & Second Laws

A bullet of mass 20 g has an initial speed of 1 ms–1, just before it starts penetrating a mud wall of thickness 20 cm. If the wall offers a mean resistance of 2.5 × 10–2 N, the speed of the bullet after emerging from the other side of the wall is close to:

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Answer: (c)

  1. Retardation a=Fm=2.5×10−20.02=1.25 m/s2a = \frac{F}{m} = \frac{2.5 \times 10^{-2}}{0.02} = 1.25\text{ m/s}^2
  2. v2=u2−2as=1−2(1.25)(0.2)=0.5v^2 = u^2 - 2as = 1 - 2(1.25)(0.2) = 0.5
  3. v=0.5≈0.7 m/sv = \sqrt{0.5} \approx 0.7\text{ m/s}. So the answer is (c) 0.7 ms−1^{-1}.
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