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Physics · LAWS OF MOTION
हिन्दीA bullet of mass \( 0.05\text{ kg} \) entering a fixed wooden block with an initial horizontal speed of \( 200\text{ m/s} \) comes to rest after penetrating a distance of \( 0.5\text{ m} \). Assuming a uniform resistive retarding force, the average resistive force exerted by the block and the stopping time are respectively:
Correct answer · Option 1
2000 N, 5.0 ms
Explanation
Using \( v^2 = u^2 + 2as \implies 0 = 200^2 + 2 a (0.5) \implies a = -40,000\text{ m/s}^2 \). Force \( F = m|a| = 0.05 \times 40000 = 2000\text{ N} \). Stopping time \( t = \frac{u}{|a|} = \frac{200}{40000} = 0.005\text{ s} = 5.0\text{ ms} \).
