Each pound of fat contains 3500 food calories. When the body metabolizes food, 7

Question

Each pound of fat contains 3500 food calories. When the body metabolizes food, 78.5% of this energy goes to heat. Suppose you decide to run without stopping, an activity that produces 1190W of metabolic power for a typical person.

For how many hours must you run to burn up 1 lb of fat?

If you followed your planned exercise program, how much heat would your body produce when you burn up a pound of fat?

if you needed to get rid of all of this excess heat by evaporating water (i.e., sweating), how many liters would you need to evaporate? The heat of vaporization of water at body temperature is 2.42106J/kg .

Explanation / Answer

A) food calories are actually in kilo calories so multiply by 1000 to get calories. Also, we know that energy = power *time so rearranging the units we get time=energy/power. they give you the power in watts and 1 watt is 1 joule/second. to get calories to joules multiply 27.5*10^7 cal by 4.186 to get number in joules. that is your energy.
11501035/1190=9664.73 seconds, just convert this to hours. i.e 161hrs

B) Heat (Q) =power *time. Q, in this case = 1190 joules/sec*9664s

C) you know the energy (11500160). divide this by 2.42*10^6 J.i.e 4.75 joules approx..... this gives you an answer in kg. in this case the conversion is 1 to 1. normally these untis cant be converted because liters is a quantity and kg is a mass.

Hope this helps!

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