Physics education research, electronic materials, and the musings of Christopher Moore, Ph.D.

A 250-kg crate rests on a surface that is inclined above the horizontal at an angle of 21.8°. A horizontal force (magnitude = 515 N and parallel to the ground, not the incline) is required to start the crate moving down the incline. What is the coefficient of static friction between the crate and the incline?