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Homework Statement
A 60 kg person is exercising in the gym, doing external work at a rate of 200W. If they have an efficiency of 20%, calculate the rate of temperature increase of their body if none of this heat was able to be transferred to their surrounds.
(a) 828 ◦C per hour. (b) 13.8 ◦C per hour. (c) 3.45 ◦C per hour. (d) 0.86 ◦C per hour.
Homework Equations
Specific Heat of human = 3.473
The Attempt at a Solution
Really basic question but I just can't wrap my head around it. One thing that confuses me is that I thought the 20% efficiency meant that 20% was used for work and that 80% was lost as heat but the last part of the question says "if none of this heat"?
I'm guessing that the answer is 13.8 because that makes the most sense -here is my attempt so far:
I multiplied specific heat and the man's mass together to get 208380J/◦C. I then worked out what 200 watts was in hours = 720,000J/H. I then found both 20% and 80% of this value (144000J/H and 576000J/h respectively) as I wasn't sure what part of the energy generated was heat. I'm not too sure on what to do here now, I know we need to get a value with temperature over hour. The only way I can see to do this by dividing one of the 2 J/H values with the J/temp value but none of those equations gives me an answer. Am I missing something really easy? Does anyone have an suggestions on how to improve with these unit conversion/problem solving questions?
Cheers