A pulley system has an efficiency of 87.5%. How much rope must be pulled if a force of 648N is needed to lift a 105 kg desk 2.46m?

Answer 1

work done on desk = m g h = 105 * 9.81 * 2.46 = 2534 Joules
so work in = 2534 / 0.875 = 2896 Joules
that is your 648 times distance your hand moved holding the rope
2896 = 648 * x
4.47 meters
I think maybe a typo, 648 N is too big, maybe 64.8 ? Any block and tackle system does better than that.