PHYSICS · Single correct · CBSE · Physics · Laws of Motion · Laws of Motion
Problem
A 6kg crate rests on a horizontal floor. A student gradually increases the horizontal pull she exerts on the crate with a rope. While the crate remains at rest, which statement best describes the magnitude of the friction force acting on the crate as the pull increases?
(a) It is constant and equal to μsmg as long as the crate is at rest.
(b) It increases in step with the pull, matching it exactly, until it reaches a maximum of μsmg.
(c) It increases with the pull but is always slightly less than the pull; when the pull finally exceeds μsmg the crate begins to move.
(d) It remains zero until the pull exceeds μsmg, then jumps to μkmg.