Q 11-04-024NEETJEE MainEAMCET 2014 (Engineering)Medium
The force required to move a body up a rough inclined plane is double the force required to prevent the body from sliding down the plane. The coefficient of friction when the angle of inclination of the plane is $60°$ is
Answer: (B) $\dfrac{1}{\sqrt{3}}$
$$mg(\sin\theta + \mu\cos\theta) = 2mg(\sin\theta - \mu\cos\theta) \;\Rightarrow\; 3\mu\cos\theta = \sin\theta$$
$$\mu = \frac{\tan 60°}{3} = \frac{\sqrt{3}}{3} = \frac{1}{\sqrt{3}}$$
Solution by Sreeraj P, M.Sc Physics