Climbing stairs is good exercise. The work you do in climbing stairs is roughly

Question

Climbing stairs is good exercise. The work you do in climbing stairs is roughly equal to your increase in potential energy. The amount of energy you actually expend is about 4 times greater that the work you accomplish (your increase in potential energy). This is due to the fact that you convert about 75% of your muscle energy into heat and 25% into mechanical work. We measure food energy (chemical energy in food) in Cal's (with a capital C) where 1000 J = 0.239 kcal = 0.239 Cal. You can note that dietary Cal is a lazy abbreviation of kcal where the "k" is just dropped. Often the capital "C" is also dropped and you are expected to understand that you are talking about dietary calories from the context.   

In this problem you are asked to calculate the amount of dietary Cal's a 70 kg person would expend in consecutively climbing two flights of stairs each with a vertical rise of 4 m.

As a point of comparison, a chocolate chip cookie might contain 300 Cal.

Explanation / Answer

Potential gained by the object will be

mgh

700*9.8*4

2744J

So net energy required by the body will be

2744*4

=10976J

Now we have

4.18J= 1cal

so

10976 J=

10976/4.18

=2625cal

or 2.6 kcal

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