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Physics · PYQ NEET UG 2025
हिन्दीThere are two inclined surfaces of equal length (\( L \)) and same angle of inclination \( 45^\circ \) with the horizontal. One of them is rough and the other is perfectly smooth. A given body takes 2 times as much time to slide down on rough surface than on the smooth surface. The coefficient of kinetic friction (\( \mu_k \)) between the object and the rough surface is close to
Correct answer · Option 4
0.75
Explanation
Time \( t \propto \frac{1}{\sqrt{a}} \). Since \( t_{\text{rough}} = 2 t_{\text{smooth}}\}, \(a_{\text{smooth}} = 4 a_{\text{rough}} \). Using \( g\sin\theta - \mu_k g\cos\theta = \frac{1}{4} g\sin\theta \) with \( \theta = 45^\circ \), we get \( \mu_k = 0.75 \).\)
