Question

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. 0.5
• D. 0.75

Answer 1

Answer: (D)

0.75

Answer 2

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