How much water has been lost from a person exercising?

  • Thread starter Thread starter kyaat
  • Start date Start date
  • Tags Tags
    Lost Water
Click For Summary
SUMMARY

The discussion centers on calculating the amount of water lost through evaporation during exercise, specifically when a person expends 180.0 kcal of heat in 30 minutes. The correct formula to use is Q = M x Lv, where Q represents heat, M is mass, and Lv is the latent heat of evaporation (539 kcal/kg). By rearranging the formula to solve for mass (M), the calculation yields a water loss of 0.334 kg. Participants emphasize the importance of correctly applying the values and understanding the rearrangement of formulas.

PREREQUISITES
  • Understanding of thermodynamics principles, specifically heat transfer.
  • Familiarity with the formula Q = M x Lv for calculating heat and mass.
  • Knowledge of latent heat of evaporation, specifically for water (539 kcal/kg).
  • Basic algebra skills for rearranging formulas.
NEXT STEPS
  • Study the concept of latent heat and its applications in thermodynamics.
  • Learn how to rearrange formulas in physics and chemistry contexts.
  • Explore practical examples of heat transfer during physical activities.
  • Investigate the physiological effects of dehydration during exercise.
USEFUL FOR

This discussion is beneficial for students in physics or chemistry courses, exercise physiologists, and anyone interested in understanding the physiological impacts of exercise on hydration and heat loss.

kyaat
Messages
2
Reaction score
0

Homework Statement


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!
 
Physics news on Phys.org
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.
 
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:

Similar threads

  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 33 ·
2
Replies
33
Views
4K
Replies
9
Views
3K
Replies
4
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 1 ·
Replies
1
Views
4K
Replies
3
Views
3K
Replies
1
Views
5K
  • · Replies 4 ·
Replies
4
Views
2K
Replies
3
Views
2K