The upper half of an inclined plane with inclination ф is perfectly smooth while the lower half is rough.

Question

The upper half of an inclined plane with inclination  ϕ is perfectly smooth while the lower half is rough. A body starting from rest at the top will again come to rest at the bottom if the coefficient of friction for the lower half is given by

(a) 2tanϕ

(b) tanϕ

(c) 2sinϕ

(d) 2cosϕ

Answer 1

(a) : For upper half smooth incline, component of
g down the incline = gsinϕ