Question

A body of mass 4kg is kept on an inclined plane of 1 in 2. When it is pulled directly up the plane by a force of 6kg wt, it moves with acceleration of $2m/s^2$. If a force of 3kg wt is applied down the plane, it moves with the acceleration ($g=10m/s^2$)

• A. $1m/s^2$
• B. $2m/s^2$
• C. $3.5m/s^2$
• D. $4.5m/s^2$

Answer 1

The correct option is D $4.5m/s^2$

When moving up the plane, the frictional force acts downwards in addition to the gravitational force.

$⟹m{a}_{up}=F_{up}-mgsin\theta -\mu mgcos\theta$

$⟹8=60-mgsin\theta -\mu mgcos\theta$

When moving down the plane, the frictional force acts upwards.

Hence, $m{a}_{down}=F_{down}+mgsin\theta -\mu mgcos\theta$

$⟹a_{down}=4.5m/s^2$