Q. Starting from rest, the time taken by a body sliding down on a rough inclined plane at $45{^\circ}$ with the horizontal is twice the time taken to travel on a smooth plane of same inclination and same distance. Then the coefficient of kinetic friction is
A) 0.25
B) 0.33
C) 0.50
D) 0.75
Explanation
(d) $Coefficient\ of\ friction\ \mu = \tan{\theta\left\lbrack 1 - \frac{1}{2^{2}} \right\rbrack}$
$Here,,\ \theta = 45{^\circ}\ \ and\ \ n = 2$
$\therefore\ \ \ \mu = \tan{45{^\circ}}\ \left\lbrack 1 - \frac{1}{2^{2}} \right\rbrack$
$= 1 - \frac{1}{4}$
$= \frac{3}{4} = 0.75$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.