Let a crate of 75
lb be dragged untill half the plane as shown and be released from that
point. Determine its speed after it slides down the plane. The coefficient
of kineic friction between the crate and plane is 1) 11.4 ft/s 

Equation of motion:
Since the crate slides, the friction force developed between the crate
and its surface is Principle of work
and energy : Force components parallel to the incilned plane 75 sin30^{o}
lb and So the speed of the crate after it slides down the plane is v = 11.4 ft/s 