Heat and work -- how much energy to climb the rope...

  • #1

Homework Statement


A standard man climbs 15 m up a vertical rope. How much energy (in cal) is dissipated as heat in a single climb if 23% of the total energy required is used to do the work? (Assume the standard man has a mass of 70 kg.)

Homework Equations


Q = mgΔh

The Attempt at a Solution


I used Q = mgΔh and took 23% of that and then converted it to calories and it was not correct. I think I am just not understanding what the question is asking for.
 

Answers and Replies

  • #2
berkeman
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if 23% of the total energy required is used to do the work?
That part doesn't make any sense. Is it copied word-for-word? Are you sure it's not 123%? How could it take less work than the change in energy?
 
  • #3
haruspex
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That part doesn't make any sense. Is it copied word-for-word? Are you sure it's not 123%? How could it take less work than the change in energy?
The wording is unclear, but I would it interpret as 23% of the energy the man expends goes into the useful work of ascending the rope.
 
  • #4
berkeman
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Ah, that would make a lot more sense! Thanks haruspex.
 
  • #5
That part doesn't make any sense. Is it copied word-for-word? Are you sure it's not 123%? How could it take less work than the change in energy?
Yeah copied it word for word I'll try what haruspex said. Thank you for the help.
 
  • #6
The wording is unclear, but I would it interpret as 23% of the energy the man expends goes into the useful work of ascending the rope.
How would I go about this without knowing the amount of energy the man expended in the first place?
 
  • #7
haruspex
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How would I go about this without knowing the amount of energy the man expended in the first place?
Just create an unknown for that and see what equation you can write.
 

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