Q. A body takes time $t$ to reach the bottom of an inclined plane of angle $\theta$ with the horizontal. If the plane is made rough, time taken now is $2t$. The coefficient of the friction of the rough surface is
A) $\frac{3}{4}\tan\theta$
B) $\frac{2}{3}\tan\theta$
C) $\frac{1}{4}\tan\theta$
D) $\frac{1}{2}\tan\theta$
Explanation
(a) $\mu = \tan\theta\left( 1 - \frac{1}{n^{2}} \right) = \tan\theta\left( 1 - \frac{1}{2^{2}} \right) = \frac{3}{4}\tan\theta$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.