# physics!

posted by .

while running a marathon, alex is producing about 900 calories per hour. 1 calorie is 4184 j. if the specific heat of the human body is 3500 j/kg x c, how many degrees celsius would alexs temperature increase if he did not sweat and ran the marathon in 3 h and 10 min? he has a mass of 75 kg.

thank god for sweat. if alex wants to release all of the caloric energy he produced so he doesnt heat up, how many litres of sweat would he need to produce and evaporate? the heat of vaporization for the water in sweat is 2.26 x 10^6 j/kg. the density of water is 1 g/ml

• physics! -

You are talking about kilocalories, not calories. (It is written as capitalized Calories when talking about nutrition and metabolic rates)

In a 3.17 hour race, the body heat generated will be
Q = 3.17h*900Cal/h*4184J/Cal = 1.19*10^7 Joules
Temperature would increase by
delta T = Q/M*C = 45.5 C

For the second question, divide Q by the heat of vaporization in J/kg. Then convert that mass to volume in liters, using the density.

## Similar Questions

1. ### science

why is a burn from steam potentially more serios than a burn from very hot water?
2. ### Physics Problem

While running, a 70.0 kg student generates thermal energy at a rate of 1200 W. To maintain a constant body temperature of 37.0 C, this energy must be removed by perspiration or other mechanisms. If these mechanisms failed and the heat …
3. ### Physics

If the air temperature is the same as the temperature of your skin (about 30 degrees Celcius), your body cannot get rid of heat by transferring it to the air. In that case, it gets rid of the heat by evaporating water (sweat). During …
4. ### Astronomy/Physics

I'd love thorough solutions to these problems, but simply providing the specific formulas that I should solve each part of the problem with would be really good too. :-) Thanks! Human energetics You are sitting down to study in the …
5. ### physics

The basal metabolic rate is the rate at which energy is produced in the body when a person is at rest. A 70.0 kg person of height 1.79 m would have a body surface area of approximately 1.90 m^2. What is the net amount of heat this …
6. ### physic problem-thermoregulation

During a dry day, a 70.0 kg athlete runs a marathon while the outside temperature is T2 = 33.2 ¢XC. The thermal power produced by the athlete's body is P = 1.05 ¡Ñ 103 W and the skin temperature is T3 = 35.5 ¢XC so that the themal …
7. ### Chemistry

How many joules (J) are needed to increase the temperature of15.0g of lead from 20 degrees celsius to 40 degrees celsius?
8. ### physics

water has a specific heat of 4184 j(kg K). How much energy is needed to increase the temperature of a kilogram of water 5 degrees celcius?