A crate of potatoes of mass 9.0 kg is on a ramp with angle of incline 30° to the horizontal. The coefficients of friction are μs = 0.69 and μk = 0.41. Find the frictional force (magnitude and direction) on the crate if the crate is at rest.

Question

magnitude N
direction

Answer 1

Wc = mg = 9kg * 9.8N/kg = 88.2 N. = Wt.
of crate.

Fc = 88.2 N. @ 30 Deg.=Force of crate.
Fp = 88.2*sin30 = 44.1 N. = Force parallel to ramp.
Fv = 88.2*cos30 = 76.4 N. = Force perpendicular to ramp.

Fs = 0.69*76.4 = 52.7 N.,up. = Force of static friction.

Fk = 0.41*76.4 = 31.3 N.,up. = Force of kinetic friction.