Question

A block of mass $m$ is kept on an inclined plane of a lift moving down with acceleration of $2m{s}^{-2}$ What should be the coefficient of friction to let the block move down with constant velocity relative to lift.

Answer 1

Suppose the angle of the inclination be$\theta$. Then according to force conservation the downward force should be equal to friction

$F=\mu N$

$mg\sin \theta =\mu mg\cos \theta$

As it is mentioned that the life goes downward with the acceleration

$2m/s^2$

Hence the acceleration due to gravity changes to

$g-2m/s^2$

By solving the above equation we get

$\mu =\tan \theta$