Question

A block of mass $m$ is placed on a rough inclined plane of inclination $\theta$ kept on the floor of the lift. The coefficient of friction between the block and the inclined plane is $\mu$. With what acceleration will the block slide down the inclined plane when the lift falls freely?

• A. Zero
• B. $g\sin \theta -mug\cos \theta$
• C. $g\sin \theta +mug\cos \theta$
• D. None of the above

Answer 1

The correct option is A Zero

If lift falls freely. Apply relative motion concept.(If we stop the lift and add opposite action on block it is relative motion.)

Since mg=mg gets cancelled.

There is no force applied on the block . Hence no friction

a=0