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Physics · LAWS OF MOTION
हिन्दीA block of mass \( 5\text{ kg} \) rests on a horizontal rough surface with coefficient of static friction \( \mu_s = 0.4 \). If a horizontal force of \( 15\text{ N} \) is applied on the block, the frictional force acting on the block is (Take \( g = 10\text{ m s}^{-2} \)):
Correct answer · Option 3
\( 15\text{ N} \)
Explanation
Maximum static friction \( f_{s,\text{max}} = \mu_s mg = 0.4 \times 5 \times 10 = 20\text{ N} \). Since applied force \( F = 15\text{ N} < f_{s,\text{max}} \), static friction self-adjusts to equal the applied force, i.e., \( 15\text{ N} \).
