20 of 20 How much water must the joggers body evaporale every minute due to his

Question

20 of 20 How much water must the joggers body evaporale every minute due to his activity? The heat of vaporization of water a body temperature is 242-10 J/kg Constants You have probably seen people jogging in extremely hot weather and wondered "Why?" As we shall see, there are good reasons not to do this When jogging strenuously, an average nunner of mass 67.0 kg and surface area 1.85 1u produces energy at a rate of up to 1340 w800%ofwhich s convered to heat. The jogger radiates heat, bu actually absorbs more from the hot air than he radiales away. At such high levels of acivity, the skin's temperature can be elevated to around 33.0 m. 2.876-10 C iestead of the usual 30 0 C. (We shall neglect conduction, which would bring even more heat into his body ] The only way for the body to get rid of this extra heat is by evaporalting water (sweating) Submit Previous Answers Request Answer X incor ct; Try Again: 2 attempts remaining Part E How many 750 lbotles of waler met he drik atter or preerably beforet) ogping for a half hour? Recall hat a liter of water has a mass of 1.00 kg botles Submit equest Anw

Explanation / Answer

Rate of energy used by the body, E = 1340 W
Rate of energy converted into heat = 80 % of E
= 0.8 x 1340 = 1072 W
Heat energy produced after 1 minute = Q = 1072 x 60
= 64320 J

Q = mLv
Where m is mass of water and Lv is the heat of vaporization at body temperature.
m = Q/Lv
= 64320 / (2.42 x 106)
= 0.02658 kg
= 26.58 g

b)
Heat energy produced after 30 minutes = Q x 30
= 1929600 J
m = Q/Lv
= (1929600) / (2.42 x 106)
= 0.797 kg
= 797 ml of water.
So he need to take at least 2 bottles

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