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

[Sam Vermeulen]

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.

 

[berkeman]

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?

 

[haruspex]

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.

 

[berkeman]

Ah, that would make a lot more sense! Thanks haruspex.

 

[Sam Vermeulen]

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.

 

[Sam Vermeulen]

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?

 

[haruspex]

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.