Physics (5th Edition)
Physics (5th Edition)
5th Edition
ISBN: 9780321976444
Author: James S. Walker
Publisher: PEARSON
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Chapter 18, Problem 57PCE

(a)

To determine

The required mechanical work of the refrigerator.

(b)

To determine

The money saved during 92day cooling session.

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A 4-ton air conditioner removes 5.06×107 J (48,000 British thermal units) from a cold environment in 1.00 h. (a) What energy input in joules is necessary to do this if the air conditioner has an energy efficiency rating (EER) of 12.0? (b) What is the cost of doing this if the work costs 10.0 cents per 3.06×106 J (one kilowatthour)? (c) Discuss whether this cost seems realistic. Note that the energy efficiency rating (EER) of an air conditioner or refrigerator is defined to be the number of British thermal units of heat transfer from a cold environment per hour divided by the watts of power input.
A 68 kg cyclist is pedaling down the road at 15 km/h, using a total metabolic power of 480 W. A certain fraction of this energy is used to move the bicycle forward, but the balance ends up as thermal energy in his body, which he must get rid of to keep cool. On a very warm day, conduction, convection, and radiation transfer little energy, and so he does this by perspiring, with the evaporation of water taking away the excess thermal energy. To keep from overheating, the cyclist must get rid of the excess thermal energy generated in his body. If he cycles at this rate for 2 hours, how many liters of water must he perspire, to the nearest 0.1 liter?A. 0.4 L                   B. 0.9 L                 C. 1.1 L            D. 1.4 L
A 68 kg cyclist is pedaling down the road at 15 km/h, using a total metabolic power of 480 W. A certain fraction of this energy is used to move the bicycle forward, but the balance ends up as thermal energy in his body, which he must get rid of to keep cool. On a very warm day, conduction, convection, and radiation transfer little energy, and so he does this by perspiring, with the evaporation of water taking away the excess thermal energy. As he cycles at a constant speed on level ground, at what rate is chemical energy being converted to thermal energy in his body, assuming a typical efficiency of 25% for the conversion of chemical energy to the mechanical energy of motion?A. 480 W             B. 360 W             C. 240 W            D. 120 W

Chapter 18 Solutions

Physics (5th Edition)

Ch. 18 - Prob. 1CQCh. 18 - Heat is added to a substance. Is it safe to...Ch. 18 - Are there thermodynamic processes in which all the...Ch. 18 - An ideal gas is held in an insulated container at...Ch. 18 - Prob. 5CQCh. 18 - Which law of thermodynamics would be violated if...Ch. 18 - Heat engines always give off a certain amount of...Ch. 18 - Prob. 8CQCh. 18 - Which law of thermodynamics is most pertinent to...Ch. 18 - Which has more entropy: (a) popcorn kernels, or...Ch. 18 - Prob. 1PCECh. 18 - A gas expands, doing 100 J of work. How much heat...Ch. 18 - A swimmer does 7.7 105 J of work and gives off...Ch. 18 - When 1310 J of heat are added to one mole of an...Ch. 18 - Three different processes act on a system. (a) In...Ch. 18 - A container holds a gas consisting of 2.85 moles...Ch. 18 - The Charge on Adhesive Tape When adhesive tape is...Ch. 18 - Predict/Calculate One mole of an ideal monatomic...Ch. 18 - Prob. 9PCECh. 18 - A cylinder contains 4.0 moles of a monatomic gas...Ch. 18 - An ideal gas is taken through the three processes...Ch. 18 - Figure 18-26 shows three different multistep...Ch. 18 - Prob. 13PCECh. 18 - An ideal gas is compressed at constant pressure to...Ch. 18 - As an ideal gas expands at constant pressure from...Ch. 18 - A system consisting of an ideal gas at the...Ch. 18 - Prob. 17PCECh. 18 - (a) Find the work done by a monatomic ideal gas as...Ch. 18 - Prob. 19PCECh. 18 - Predict/Calculate If 9.50 moles of a monatomic...Ch. 18 - Suppose 118 moles of a monatomic ideal gas undergo...Ch. 18 - A weather balloon contains an ideal gas and has a...Ch. 18 - Prob. 23PCECh. 18 - During an adiabatic process, the temperature of...Ch. 18 - An ideal gas follows the three-part process shown...Ch. 18 - With the pressure held constant at 260 kPa, 43 mol...Ch. 18 - Prob. 27PCECh. 18 - A system expands by 0.75 m3 at a constant pressure...Ch. 18 - Prob. 29PCECh. 18 - A certain amount of a monatomic ideal gas...Ch. 18 - An ideal gas doubles its volume in one of three...Ch. 18 - Predict/Explain You plan to add a certain amount...Ch. 18 - Find the amount of heat needed to increase the...Ch. 18 - (a) If 585 J of heat are added to 49 moles of a...Ch. 18 - A system consists of 3.5 mol of an ideal monatomic...Ch. 18 - Find the change in temperature if 170 J of heat...Ch. 18 - Gasoline Ignition Consider a short time span just...Ch. 18 - Prob. 38PCECh. 18 - Prob. 39PCECh. 18 - A monatomic ideal gas is held in a thermally...Ch. 18 - Consider the expansion of 60.0 moles of a...Ch. 18 - A Carnot engine can be operated with one of the...Ch. 18 - What is the efficiency of an engine that exhausts...Ch. 18 - An engine receives 660 J of heat from a hot...Ch. 18 - A Carnot engine operates between the temperatures...Ch. 18 - A nuclear power plant has a reactor that produces...Ch. 18 - At a coal-burning power plant a steam turbine is...Ch. 18 - Predict/Calculate A portable generator produces...Ch. 18 - Predict/Calculate The efficiency of a particular...Ch. 18 - During each cycle a reversible engine absorbs 3100...Ch. 18 - Prob. 51PCECh. 18 - The operating temperatures for a Carnot engine are...Ch. 18 - A certain Carnot engine takes in the heat Qh and...Ch. 18 - Predict/Explain (a) If the temperature in the...Ch. 18 - The refrigerator in your kitchen does 490 J of...Ch. 18 - A refrigerator with a coefficient of performance...Ch. 18 - Prob. 57PCECh. 18 - Prob. 58PCECh. 18 - An air conditioner is used to keep the interior of...Ch. 18 - A reversible refrigerator has a coefficient of...Ch. 18 - A freezer has a coefficient of performance equal...Ch. 18 - Predict/Explain (a) If you rub your hands...Ch. 18 - Predict/Explain (a) An ideal gas is expanded...Ch. 18 - Predict/Explain (a) A gas is expanded reversibly...Ch. 18 - Find the change in entropy when 1.85 kg of water...Ch. 18 - Determine the change in entropy that occurs when...Ch. 18 - Prob. 67PCECh. 18 - On a cold winters day heat leaks slowly out of a...Ch. 18 - An 88-kg parachutist descends through a vertical...Ch. 18 - Predict/Calculate Consider the air-conditioning...Ch. 18 - A heat engine operates between a high-temperature...Ch. 18 - It can be shown that as a mass m with specific...Ch. 18 - Prob. 73GPCh. 18 - Figure 18-34 Problem 74 74 CE An ideal gas has...Ch. 18 - The heat that goes into a particular Carnot engine...Ch. 18 - Predict/Calculate Consider 132 moles of a...Ch. 18 - Prob. 77GPCh. 18 - Prob. 78GPCh. 18 - Predict/Calculate Engine A has an efficiency of...Ch. 18 - Nuclear Versus Natural Gas Energy Because of...Ch. 18 - A freezer with a coefficient of performance of...Ch. 18 - Entropy and the Sun The surface of the Sun has a...Ch. 18 - Prob. 83GPCh. 18 - A cylinder with a movable piston holds 2.95 mol of...Ch. 18 - Making Ice You place 0.410 kg of cold water inside...Ch. 18 - An inventor claims a new cyclic engine that uses...Ch. 18 - Predict/Calculate A small dish containing 530 g of...Ch. 18 - Predict/Calculate An ideal gas is taken through...Ch. 18 - One mole of an ideal monatomic gas follows the...Ch. 18 - When a heat Q is added to a monatomic ideal gas at...Ch. 18 - The Carnot Cycle Figure 18-36 shows an example of...Ch. 18 - A Carnot engine and a Carnot refrigerator operate...Ch. 18 - Prob. 93PPCh. 18 - Energy from the Ocean Whenever two objects are at...Ch. 18 - Prob. 95PPCh. 18 - Energy from me Ocean Whenever two objects are at...Ch. 18 - Predict/Calculate Referring to Example 18-21...Ch. 18 - Predict/Calculate Referring to Example 18-21...
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