Question

The angle of inclination of the plane, at which the body begins to move down the plane, is called

(a) angle of friction

(b) angle of repose

(c) angle of projection

(d) none of the mentioned

I have been asked this question in final exam.

My question comes from Friction and Double Hooke’s Joint topic in section Friction of Machine Kinematics

Answer 1

Correct option is (a) angle of friction

Easy explanation: Consider that a body A of weight (W) is resting on a horizontal plane B. If a horizontal force P is applied to the body, no relative motion will take place until the applied force P is equal to the force of friction F, acting opposite to the direction of motion. The magnitude of this force of friction is F = μ.W = μ.RN, where RN is the normal reaction.