How many grams of carbohydrate does a person of mass 75 kg need to metabolize to climb five flights of stairs (15 m height increase)? Each gram of carbohydrate provides 17.6 kJ of energy. Assume 10.0% efficiency—that is, 10.0% of the available chemical energy in the carbohydrate is converted to mechanical energy.

Question

g

What happens to the other 90% of the energy?

Could someone show me how to do this please. Thanks. I have a hard time figuring it out.

physics - Count Iblis, Friday, June 8, 2012 at 2:07pm

The person needs to do an amount of work of W = 75 kg * 15 m * 9.81 m/s^2 against gravity.

Per gram of carbohydrates, you have available 10% of 17.6 KJ to do mechanical work, so you need to divide W by 1.76 KJ to find the amount of carbohydrates needed in grams.

The other 90% converted to heat.

part a i tried it and it gave me 11036.25 that was wrong i put 110.36 that was wrong so i don't know how to do it and the answer has to be in g???please help. Thank you

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Answer 1

PE=m•g•h=75•9.81•15=11036 J.
11036 J is 10% ,
x is 100%
x=110360 J.
110360/17600=6.27 g