A bullet of mass 10 g leaves a rifle at an initial velocity of 1000 m/s and strikes the earth at the same level with a velocity of 500 m/s. The work done in joule overcoming the resistance of air will be (a) 375 (b) 3750 (c) 5000 (d) 500

Answer: (b). Same level, so gravity does no net work; the KE loss is the work against air resistance. W = 1/2m(u² - v²) = 1/2(0.01)(10⁶ - 2.5 × 10⁵) W = 0.005 × 7.5 × 10⁵ = 3750 J, so the answer is (b).

A bullet of mass 10 g leaves a rifle at an initial velocity of 1000… | NEET 1989 (AIPMT)

Q32NEET 1989 · AIPMTEasy

Work-Energy Theorem

A bullet of mass $10\text{ g}$ leaves a rifle at an initial velocity of $1000\text{ m/s}$ and strikes the earth at the same level with a velocity of $500\text{ m/s}$ . The work done in joule overcoming the resistance of air will be

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Answer: (b)

Same level, so gravity does no net work; the KE loss is the work against air resistance.
$W = \frac{1}{2}m(u^2 - v^2) = \frac{1}{2}(0.01)(10^6 - 2.5 \times 10^5)$
$W = 0.005 \times 7.5 \times 10^5 = 3750\text{ J}$ , so the answer is (b).

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