Physics of Everyday Phenomena
9th Edition
ISBN: 9781259894008
Author: W. Thomas Griffith, Juliet Brosing Professor
Publisher: McGraw-Hill Education
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Textbook Question
Chapter 11, Problem 1SP
Suppose that a typical automobile engine operates at an efficiency of 19%. One gallon of gasoline releases approximately 120 MJ of heat when it is burned. (A megajoule, MJ, is a million joules.)
a. Of the energy available in a gallon of gas, how much energy can be used to do useful work in moving the automobile and running its accessories?
b. How much heat per gallon is released to the environment in the exhaust gases and via the
c. If the car is moving at constant speed, how is the work output of the engine used?
d. Would you expect the efficiency of the engine to be greater on a very hot day or on a cold day? Explain. (There may be competing effects at work.)
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Suppose you require 2500 food Calories per day.
a. What is your average power, in watts?
b. How much energy, in joules, do you require from food in a year? Counting all forms of energy (such as gasoline, electricity, and energy for heating), the average person consumes about 350
billion joules of energy each year. Compare this value to the energy needed from food alone.
a. What is your average power, in watts?
Approximately 121 watts
(Round to the nearest whole number as needed.)
b. The energy required from food is approximately billion joules per year.
(Round to the nearest tenth as needed.)
Suppose a woman does 650 J of work and 9300 J of heat is transferred from her into the environment in the process.
a. What is the change in her internal energy, in joules, assuming she does not consume any food?
b. What is her percent efficiency?
Heating The amount of chemical potential energy stored in one gallon of heating oil is approximately 130 MJ. This is the amount of energy released as heat during combustion. (Note: 1.0 kWh = 3600 kW-sec = 3600 kJ = 3.6 MJ. Verify this equivalency and use it to answer the following question.) a. Suppose that during the winter, heating your home with oil may require an average of 6 gallons of oil per day. Assuming that to be the case, what is the average daily energy consumption? (Express your answer in kWh.) b. If the cost of heating oil is $3.00/gallon, what is the daily cost to heat your home? Use this information to find the cost of heating with oil in units of cents/kWh.
Chapter 11 Solutions
Physics of Everyday Phenomena
Ch. 11 - Prob. 1CQCh. 11 - Prob. 2CQCh. 11 - In applying the first law of thermodynamics to a...Ch. 11 - Is the total amount of heat released by a heat...Ch. 11 - From the perspective of the first law of...Ch. 11 - Which motor in a hybrid vehiclethe electric or...Ch. 11 - Prob. 7CQCh. 11 - Prob. 8CQCh. 11 - Prob. 9CQCh. 11 - Prob. 10CQ
Ch. 11 - Prob. 11CQCh. 11 - Is it possible for the efficiency of a heat engine...Ch. 11 - Can a Carnot engine operate in an irreversible...Ch. 11 - Does a gasoline-burning automobile engine operate...Ch. 11 - Which would have the greater efficiencya Carnot...Ch. 11 - If we want to increase the efficiency of a Carnot...Ch. 11 - Is a heat pump the same thing as a heat engine?...Ch. 11 - Is a heat pump essentially the same thing as a...Ch. 11 - When a heat pump is used to heat a building, where...Ch. 11 - Is it possible to cool a closed room by leaving...Ch. 11 - Prob. 21CQCh. 11 - Prob. 22CQCh. 11 - Prob. 23CQCh. 11 - Prob. 24CQCh. 11 - Which has the higher entropy, a deck of cards in...Ch. 11 - A hot cup of coffee is allowed to cool down, thus...Ch. 11 - When a substance freezes, the molecules become...Ch. 11 - Which would normally have the greater thermal...Ch. 11 - In what ways is a nuclear power plant similar to a...Ch. 11 - What is the distinction between high-grade heat...Ch. 11 - Prob. 31CQCh. 11 - Prob. 32CQCh. 11 - Is an automobile engine a perpetual-motion...Ch. 11 - Prob. 34CQCh. 11 - Prob. 35CQCh. 11 - The water draining from the bottom of the pond...Ch. 11 - Prob. 37CQCh. 11 - In one cycle, a heat engine takes in 1200 J of...Ch. 11 - A heat engine with an efficiency of 28% does 700 J...Ch. 11 - In one cycle, a heat engine takes in 800 J of heat...Ch. 11 - A heat engine with an efficiency of 35% takes in...Ch. 11 - In one cycle, a heat engine does 700 J of work and...Ch. 11 - A Carnot engine takes in heat at a temperature of...Ch. 11 - A Carnot engine takes in heat from a reservoir at...Ch. 11 - A Carnot engine operates between temperatures of...Ch. 11 - A heat pump takes in 450 J of heat from a...Ch. 11 - In each cycle of its operation, a refrigerator...Ch. 11 - A typical electric refrigerator (see fig. 11.9)...Ch. 11 - A typical nuclear power plant delivers heat from...Ch. 11 - An ocean thermal-energy power plant takes in warm...Ch. 11 - An engineer designs a heat engine using flat-plate...Ch. 11 - Suppose that a typical automobile engine operates...Ch. 11 - Prob. 2SPCh. 11 - A Carnot engine operating in reverse as a heat...Ch. 11 - In section 11.3, we showed that a violation of the...Ch. 11 - Suppose that an oil-fired power plant is designed...
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