Muscles opperating with efficiency of 18%

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Muscles operate at an efficiency of 18% when converting stored chemical energy into work. For a person weighing 63.6 kg ascending to a height of 21.0 m, the potential energy gained is calculated to be approximately 13088.88 J. To determine the required chemical energy, the efficiency must be considered; thus, to achieve this potential energy, about 72716 J of chemical energy is necessary. The calculations confirm that the 18% efficiency is crucial for determining the total energy expenditure. Understanding this efficiency is essential for solving similar problems related to energy conversion in muscular activity.
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Homework Statement

Muscles operate with an efficiency of about 18.0 percent in converting stored chemical energy into work. How much chemical energy will be expended by a 63.6 kg person in the process of ascending several flights of stairs to a height of 21.0m?

Homework Equations

pe= mgh(initial)



The Attempt at a Solution

pe=13088.88 J i wasnt sure if the 18% had anything to do with the problem or not
 
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The 18% are relevant.

13088.88 J is the potential energy the person gains. However, the question asks for the chemical energy.

Muscles can convert this chemical energy into work with 18% efficiency - if you expend 100 J of chemical energy, you can gain 18 J of potential energy (at least according to this problem). How much chemical energy to you need to gain 13088.88 J of potential energy?
 
i think 2355.10??
 
no wait i got 72716 J...i think that's right then
 
yup that works thanks!
 

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