# Homework Help: How much water has been lost from a person exercising?

1. Sep 22, 2008

### kyaat

1. The problem statement, all variables and given/known data
During exercise a person may give off 180.0 kcal of heat in 30.0 minutes by evaporation of water from the skin. How much water has been lost? The latent heat of evaporation of water is 539 kcal/kg.

2. I believe the formula to use is Q=MxLv

3. I started with the above formula, but already got stuck on whether this formula needs to be re-arranged or not? Maybe Q=ML?
Q=(180.0kCal)(539kCal/kg)
= 0.334kg

I'm just not sure if this is complete or am i missing something? Any help would be great, this assignment is due 4pm today!

2. Sep 22, 2008

### Topher925

I believe you have the right answer although I don't understand your method? You are solving for the mass, M not for heat, Q.

3. Sep 22, 2008

### kyaat

Oops, I meant to write: M=QL where,Q=180.0Kcal and L=539kCal/g?

I'm having trouble figuring out where to use given values in a formula and re-arranging formulas as we haven't gone over it in class yet..

Thanks for your help!

Last edited: Sep 22, 2008