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# Bicycling on a Warm Day. If the air temperature is the ISBN: 9780321675460 31

## Solution for problem 42E Chapter 17

University Physics | 13th Edition

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Problem 42E

Bicycling on ?a ?Warm Day?. If the air temperature is the same as the temperature of your skin (about 30°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-kg person’s body produces energy at a rate of about 500 W due to metabolism, 80% of which is converted to heat. (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 × 106 J/kg. (b) The evaporated water must, of course, be replenished, or the person will dehydrate. How many 750-mL bottles of water must the bicyclist drink per hour to replenish the lost water? (Recall that the mass of a liter of water is 1.0 kg.)

Step-by-Step Solution:

Solution to 42E Step 1 Rate of production of energy =500W Percentage of energy converted to heat =80% Amount of energy converted to heat = 500x0.8=400W Step 2 (a) 6 Heat of vaporization of water =2.42x10 J/kg Thus 2.42x10 Joules of heat is required for vaporizing 1kg of water. 6 Energy to be removed in 1h=400/3600 =1.44X10 J Therefore, Mass of water to be vaporized,M =1.44X10 J/2.42x10 J/kg 6 M=0.59kg

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##### ISBN: 9780321675460

The answer to “Bicycling on ?a ?Warm Day?. If the air temperature is the same as the temperature of your skin (about 30°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-kg person’s body produces energy at a rate of about 500 W due to metabolism, 80% of which is converted to heat. (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 × 106 J/kg. (b) The evaporated water must, of course, be replenished, or the person will dehydrate. How many 750-mL bottles of water must the bicyclist drink per hour to replenish the lost water? (Recall that the mass of a liter of water is 1.0 kg.)” is broken down into a number of easy to follow steps, and 149 words. This textbook survival guide was created for the textbook: University Physics, edition: 13. This full solution covers the following key subjects: Water, heat, body, Person, rid. This expansive textbook survival guide covers 26 chapters, and 2929 solutions. Since the solution to 42E from 17 chapter was answered, more than 366 students have viewed the full step-by-step answer. The full step-by-step solution to problem: 42E from chapter: 17 was answered by , our top Physics solution expert on 05/06/17, 06:07PM. University Physics was written by and is associated to the ISBN: 9780321675460.

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