The work output of a lever used to lift books is 30 Joules and the work input is 60 Joules. What is the efficiency of this lever?

50%

Explanation:

Given parameters:

Work output  = 30J

Work input  = 60J

Unknown:

Efficiency of the lever  = ?

Solution:

To solve this problem, the efficiency is taken as the ratio of the work output to that of the work input;

 Efficiency  = Work output / Work input  x 100

Efficiency  =  x 100  = 50%

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