By means of a lever, a man applies 60N at one end moving the lever 1m, to move a 200N rock at the other end 0.2m. What is the efficiency ?

Answer 1

work output = 200 N * .2 m = 40 Joules
work input = 60 N * 1 m = 60 Joules
efficiency = 40/60 * 100 = 66.7 %