1. The problem statement, all variables and given/known data A loaded ore car has a mass of 950 kg and rolls on rails with negligible friction. It starts from rest and is pulled up a mineshaft by a cable connected to a winch. The shaft is inclined at 30o above the horizontal. The car accelerates uniformly to a speed of 2.20 m/s in 12.0 s and then continues at constant speed. (a) What power must the winch motor provide when the car is moving at constant speed? (b) What maximum power must the winch motor provide? (c) What total energy has transferred out of the winch motor by work by the time the car moves off the end of the track, which is of length 1250 m? 2. Relevant equations P=W/t W=ΔK+ΔU v=vo+at x=xo+vot+½at2 Sinθ=O/H 3. The attempt at a solution I'm okay with (a), but I'm working on part (b). I assume that the max power the winch must provide can be found by considering the total change in mechanical energy of the system over a time t. My result is, Pmax=½mv[(v/t)+gsinθ] This gives me half of the max power. Does the total change in mechanical energy of the system not govern the max power output of the winch? Does the net force on the cart govern the max power the winch must provide?