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Please show steps and explain reasoning behind methods used. I want to be able t

ID: 2245818 • Letter: P

Question

Please show steps and explain reasoning behind methods used. I want to be able to make the connection on my own not just plug the numbers in for a solution.

If the air temperature is the same as the temperature of your skin (about 30.0?C), 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 bicycling, a typical 70.0kg  person's body produces energy at a rate of about 505W  due to metabolism, 80.5%  of which is converted to heat.
Part A
How many kilograms of water must the person's body evaporate in an hour to get rid of this heat? The heat of vaporization of water at body temperature is 2.42 Please show steps and explain reasoning behind methods used. I want to be able to make the connection on my own not just plug the numbers in for a solution.

If the air temperature is the same as the temperature of your skin (about 30.0?C), 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 bicycling, a typical 70.0kg  person's body produces energy at a rate of about 505W  due to metabolism, 80.5%  of which is converted to heat. Please show steps and explain reasoning behind methods used. I want to be able to make the connection on my own not just plug the numbers in for a solution.

If the air temperature is the same as the temperature of your skin (about 30.0?C), 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 bicycling, a typical 70.0kg  person's body produces energy at a rate of about 505W  due to metabolism, 80.5%  of which is converted to heat. Please show steps and explain reasoning behind methods used. I want to be able to make the connection on my own not just plug the numbers in for a solution.

If the air temperature is the same as the temperature of your skin (about 30.0?C), 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 bicycling, a typical 70.0kg  person's body produces energy at a rate of about 505W  due to metabolism, 80.5%  of which is converted to heat.
Part A
How many kilograms of water must the person's body evaporate in an hour to get rid of this heat? The heat of vaporization of water at body temperature is 2.42
Part A
How many kilograms of water must the person's body evaporate in an hour to get rid of this heat? The heat of vaporization of water at body temperature is 2.42

Explanation / Answer

The waste heat is given by 500 W x0.8 = 400 W

That is 400 J/s that must be taken away. Now 1 hour has 3600 seconds so teh total amount of energy that needs to be removed is

E = 400 J/s x 3600 s = 1.44x10^6 J

Heat of vaporization is givne as H = 2.42x10^6 J/kg so the amount of water needed is

m = E/H = 0.595 kg

Since 1 L of water has a mass of 1 kg, the bicyclist needs drink only one 750 mL bottle/hour