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Physics · WORK, ENERGY AND POWER
हिन्दीA raindrop of mass \( 1.00\text{ g} \) falls from a height of \( 1.00\text{ km} \) from rest and hits the ground with a speed of \( 50.0\text{ m s}^{-1} \). Taking \( g = 10\text{ m s}^{-2} \), the work done by the unknown resistive force of the air is:
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Correct answer · Option C
\( -8.75\text{ J} \)
Explanation
Change in kinetic energy \( \Delta K = \frac{1}{2}mv^2 = \frac{1}{2}(10^{-3})(2500) = 1.25\text{ J} \). Work done by gravity is \( W_g = mgh = (10^{-3})(10)(10^3) = 10.0\text{ J} \). By work-energy theorem, \( W_r = \Delta K - W_g = 1.25 - 10.0 = -8.75\text{ J} \).
