A 50.5-kg crate rests on a level floor at a shipping dock. The coefficients of static and kinetic friction are 0.624 and 0.364, respectively. What horizontal pushing force is required to (a) just start the crate moving and (b) slide the crate across the dock at a constant speed?

1 answer

Wb = M*g = 50.5 * 9.8 = 494.9 N. = Normal force, Fn.

Fs = u*Fn = 0.624 * 494.9 = 308.8 N. =
Force of static friction.

Fk = 0.364 * 494.9 = 180.1 N.

a. F-Fs = M*a.
F-308.8 = M*0 = 0
F = 308.8 N.

b. F-Fk = M*a.
F-180.1 = M*0 = 0.
F = 180.1 N.