Question

A weight W rests on a rough horizontal plane. If the angle of friction be θ , the least force that will move the body along the plane will be(a) W cos θ (b) W cot θ(c) W tan θ(d) W sin θ

Answer 1

option is b wcot theta

Answer 2

Weight = W resting on a rough horizontal plane ( Given)

Angle of friction = θ

Thus,

F = mg and mg = W

Angle of friction = Angle of repose

When a body is kept on an inclined plane inclined at an angle equal to angle of repose then it is ready to move.

Therefore,

F = mg × sinθ

F = W sinθ

The least force that will  move body along plane is Wsinθ