Question

If the efficiency of a lever is 30% and 560 J is used to move the lever, what is the work output?
A) 18.7J
B) 168 J
C) 1,867 J
D) 16,800 J

Answer 1

If the efficiency is 30%, then 30% of the work you put into it comes out
in the form of useful work, and the other 70% turns into forms of energy
that you can't use to do the job ... like heat.

30% of 560 J = 168 J (B)