Q. Starting from rest, a body slides down a $45{^\circ}$ inclined plane in twice the time it takes to slide down the same distance in the absence of friction. The coefficient of friction between the body and the inclined plane is
A) 0.33
B) 0.25
C) 0.75
D) 0.80
Explanation
(c) $\mu = \tan\theta\left( 1 - \frac{1}{n^{2}} \right)$
$\theta = 45{^\circ}$ and $n = 2$ [Given]
$\therefore\mu = \tan{45{^\circ}}\left( 1 - \frac{1}{2^{2}} \right) = 1 - \frac{1}{4} = \frac{3}{4} = 0.75$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.