OnlineCBT
Physics · LAWS OF MOTION
हिन्दीA block of mass \( m = 2\text{ kg} \) is pressed against a rough vertical wall by applying a horizontal force \( F \). The coefficient of static friction between the block and the wall is \( \mu_s = 0.4 \). Taking \( g = 10\text{ m/s}^2 \), find the minimum horizontal force \( F_{\min} \) required to keep the block stationary. If a force \( F = 100\text{ N} \) is actually applied, calculate the magnitude of friction force acting on the block.
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Correct answer · Option A
\( 50\text{ N} \) and \( 20\text{ N} \)
Explanation
For vertical equilibrium: \( f_s = mg = 20\text{ N} \). Maximum static friction \( f_{s,\max} = \mu_s F = 0.4 F_{\min} = 20 \implies F_{\min} = 50\text{ N} \). When \( F = 100\text{ N} \), \( f_{s,\max} = 40\text{ N} \). Since required force is \( 20\text{ N} \le 40\text{ N} \), static friction self-adjusts to \( 20\text{ N} \).
