Question

37. A block of mass m is at rest on a rough inclined
plane of angle of inclination e. If coefficient of friction
between the block and the inclined plane is u, then
the minimum value of force along the plane required
to move the block on the plane is (tano <u)
(1) mg[ucose – sino] (2) mg[sino + ucoso]
(3) mg[ucose + sino] (4) mg[sino - ucoso]
Here how do we know that whether the block is moving upward or downwards​

Answer 1

Answer:

required force F will act along Fs (force due to static friction) and in opposite direction will be mgsinθ

"along the plane" means the block is moving upwards

"down the plane" mean the block is moving downwards

so for upwards

F=Fs−mgsinθ=μmgcosθ−mgsinθ

=mg(μcosθ−sinθ)

Hence,

option A is correct answer.