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Physics · WORK, ENERGY AND POWER
हिन्दीA bullet of mass \( 40.0\text{ g} \) travelling at \( 250\text{ m s}^{-1} \) penetrates a thick wooden target of thickness \( 5.0\text{ cm} \) and emerges with only \( 16\% \) of its initial kinetic energy. The average resistive force exerted by the target on the bullet is:
Correct answer · Option 1
\( 2.1\times 10^4\text{ N} \)
Explanation
\( K_i = \frac{1}{2}(0.040)(250)^2 = 1250\text{ J} \). \( K_f = 0.16 \times 1250 = 200\text{ J} \). Work done by resistance \( W = -F_{\text{avg}} d = K_f - K_i = -1050\text{ J} \implies F_{\text{avg}} = \frac{1050}{0.05} = 21000\text{ N} = 2.1\times 10^4\text{ N} \).
