Worked Examples on Efficiency

1. The work input of a machine is 800J. If the work output is 200J. Calculate the efficiency of the machine.

SOLUTION

Work output = 200J; work input =800J

Efficiency = (work output /work input) x 100%

       = (200J / 800J) X 100%

       = 25%

1. The work input of a machine is 100J.If 20J is used to overcome friction. Calculate the efficiency of the machine.

SOLUTION

Work input = 100J

Work output = work input – friction

          = 100J-20J

          = 80j

Efficiency = (work output / work input) x 100%

          = (80J /100) X 100%

          = 80%