Q 11-04-026NEETJEE MainEAMCET 2008 (Engineering)Top questionEasy
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 the same inclination and the same distance. Then the coefficient of kinetic friction is
Answer: (D) $0.75$
Same distance from rest, so $a_{smooth} = 4\,a_{rough}$:
$$g\sin 45° = 4g(\sin 45° - \mu_k\cos 45°) \;\Rightarrow\; 1 = 4(1 - \mu_k) \;\Rightarrow\; \mu_k = 0.75$$
Solution by Sreeraj P, M.Sc Physics