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MECHANICAL EFFICIENCY EXAMPLES
Suppose that a system is being designed to output 100 ft − lbs. Once built, designers realize that it is only outputting 87ft − lbs because of irreversibilities that were not taken into account. Calculate the mechanical efficiency of this system.
Mechanical Efficiency = (Work Output)/(Ideal Work Output)
Mechanical Efficiency = (87 ft − lbs)/(100 ft − lbs)
Mechanical Efficiency = 0.87
By multiplying times 100 one can write this number as a percentage
Answer: This engine has a mechanical efficiency of 87%.