physics
posted by Becky on .
A crate of potatoes of mass 13.0 kg is on a ramp with angle of incline 30° to the horizontal. The coefficients of friction are μs = 0.76 and μk = 0.35. Find the frictional force (magnitude and direction) on the crate if the crate is sliding up the ramp.

the crate is sliding, so μk (the kinetic coefficient) is the relevant one
the direction of the frictional force is OPPOSITE to the direction of motion
the magnitude of the force is: the normal force of the crate on the ramp [m * g * cos(30º)]; multiplied by the coefficient of kinetic friction (μk)