Question

Starting from rest, the time taken by a body sliding down on a rough inclined plane at $45$ 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. $0.75$

Answer 1

The correct option is D $0.75$

$\mu =\tan \theta (1-\frac{1}{n^2})$
Here, $\theta =45$ and $n=2$
$\therefore \mu =\tan 45(1-\frac{1}{2^2})$
$=1-\frac{1}{4}=\frac{3}{4}=0.75$