Steve does 80 J of work to a rope threaded through a pulley and attached to a crate of anvils. The tension of the rope is 10 N and the crate rises 4 m while Steve pulls. What is the efficiency of the pulley? [Hint: how much work was done on the crate?] a) (A) 0.07 or 7 %
b) (B) 0.2 or 20 %
c) (C) 0.5 or 50 %
d) (D) 1 or 100 %