Physics for Scientists and Engineers with Modern Physics
4th Edition
ISBN: 9780131495081
Author: Douglas C. Giancoli
Publisher: Addison-Wesley
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Chapter 20, Problem 15Q
To determine
To explain how it is realized that the air conditioner in the middle of the room cannot cool the room.
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What appliance can actually cool a room? A refrigerator with the door open, an air conditioner in the middle of the room or an air conditioner partially exposed to the outside? Explain.
Brewed coffee is often too hot to drink right away. You can cool it with an ice cube, but this dilutes it. Or you can buy a device that will cool your coffee without dilution—a 200 g aluminum cylinder that you take from your freezer and place in a mug of hot coffee. If the cylinder is cooled to –20°C, a typicalfreezer temperature, and then dropped into a large cup of coffee (essentially water, with a mass of 500 g) at 85°C, what is the final temperature of the coffee?
You just took a jar out of the fridge but you are unable to open it. You then decide to leave run hot water over the lid to open it. Why does it work?
Chapter 20 Solutions
Physics for Scientists and Engineers with Modern Physics
Ch. 20.2 - An adiabatic process is defined as one in which no...Ch. 20.3 - A motor is running with an intake temperature TH =...Ch. 20.6 - A 1.00.kg piece of ice at 0C melts very slowly to...Ch. 20.9 - Prob. 1EECh. 20 - Prob. 1QCh. 20 - Can you warm a kitchen in winter by leaving the...Ch. 20 - Would a definition of heat engine efficiency as e...Ch. 20 - What plays the role of high-temperature and...Ch. 20 - Which will give the greater improvement in the...Ch. 20 - The oceans contain a tremendous amount of thermal...
Ch. 20 - Discuss the factors that keep real engines from...Ch. 20 - Prob. 8QCh. 20 - Describe a process in nature that is nearly...Ch. 20 - (a) Describe how heat could be added to a system...Ch. 20 - Suppose a gas expands to twice its original volume...Ch. 20 - Give three examples, other than those mentioned in...Ch. 20 - Which do you think has the greater entropy, 1 kg...Ch. 20 - (a) What happens if you remove the lid of a bottle...Ch. 20 - Prob. 15QCh. 20 - Prob. 16QCh. 20 - Prob. 17QCh. 20 - The first law of thermodynamics is sometimes...Ch. 20 - Powdered milk is very slowly (quasistatically)...Ch. 20 - Two identical systems are taken from state a to...Ch. 20 - It can he said that the total change in entropy...Ch. 20 - Use arguments, other than the principle of entropy...Ch. 20 - (I) A heat engine exhausts 7800 J of heat while...Ch. 20 - (I) A certain power plant puts out 580 MW of...Ch. 20 - (II) A typical compact car experiences a total...Ch. 20 - (II) A four-cylinder gasoline engine has an...Ch. 20 - (II) The burning of gasoline in a car releases...Ch. 20 - (II) Figure 2017 is a PV diagram for a reversible...Ch. 20 - (III) The operation of a diesel engine can be...Ch. 20 - (I) What is the maximum efficiency of a heat...Ch. 20 - (I) It is not necessary that a heat engines hot...Ch. 20 - (II) A heal engine exhausts its heat at 340C and...Ch. 20 - (II) (a) Show that the work done by a Carnot...Ch. 20 - (II) A Carnot engines operating temperatures are...Ch. 20 - (II) A nuclear power plant operates at 65% of its...Ch. 20 - (II) A Carnot engine performs work at the rate of...Ch. 20 - (II) Assume that a 65 kg hiker needs 4.0 103 kcal...Ch. 20 - (II) A particular car does work at the rate of...Ch. 20 - (II) A heat engine utilizes a heat source at 580C...Ch. 20 - (II) The working substance of a certain Carnot...Ch. 20 - (III) A Carnot cycle, shown in Fig. 20-7, has the...Ch. 20 - (III) One mole of monatomic gas undergoes a Carnot...Ch. 20 - (III) In an engine that approximates the Otto...Ch. 20 - (I) If an ideal refrigerator keeps its contents at...Ch. 20 - (I) The low temperature of a freezer cooling coil...Ch. 20 - (II) An ideal (Carnot) engine has an efficiency of...Ch. 20 - (II) An ideal heal pump is used to maintain the...Ch. 20 - (II) A restaurant refrigerator has a coefficient...Ch. 20 - (II) A heat pump is used to keep a house warm at...Ch. 20 - (II) (a) Given that the coefficient of performance...Ch. 20 - (II) A Carnot refrigerator (reverse of a Carnot...Ch. 20 - (II) A central heat pump updating as an air...Ch. 20 - (II) What volume of water at 0C can a freezer make...Ch. 20 - (I) What is the change in entropy of 250g of steam...Ch. 20 - (I) A 7.5-kg box having an initial speed of 4.0m/s...Ch. 20 - (I) What is the change in entropy of 1.00 m3 of...Ch. 20 - (II) If 1.00m3 of water at 0C is frozen and cooled...Ch. 20 - (II) If 0.45kg f water at 100C is changed by a...Ch. 20 - (II) An aluminum rod conducts 9.50 cal/s from a...Ch. 20 - (II) A 2.8-kg piece of aluminum at 43.0C is placed...Ch. 20 - (II) An ideal gas expands isothermally (T = 410 K)...Ch. 20 - (II) When 2.0 kg of water at 12.0C is mixed with...Ch. 20 - (II) (a) An ice cube of mass m at 0C is placed in...Ch. 20 - (II) The temperature of 2.0mol of an ideal...Ch. 20 - (II) Calculate the change in entropy of 1.00kg of...Ch. 20 - (II) An ideal gas of n moles undergoes the...Ch. 20 - (II) Two samples of an ideal gas are initially at...Ch. 20 - (II) A 150-g insulated aluminum cup at 15C is...Ch. 20 - (II) (a) Why would you expect the total entropy...Ch. 20 - (II) 1.00 mole of nitrogen (N2) gas and 1.00 mole...Ch. 20 - (II) Thermodynamic processes are sometimes...Ch. 20 - (III) The specific heat per mole of potassium at...Ch. 20 - (III) Consider an ideal gas of n moles with molar...Ch. 20 - (III) A general theorem states that the amount of...Ch. 20 - (III) Determine the work available in a 3.5-kg...Ch. 20 - (I) Use Eq. 2014 to determine the entropy of each...Ch. 20 - (II) Suppose that you repeatedly shake six coins...Ch. 20 - (II) Calculate the relative probabilities, when...Ch. 20 - (II) (a) Suppose you have four coins, all with...Ch. 20 - Prob. 58PCh. 20 - (II) Energy may be stored for use during peak...Ch. 20 - (II) Solar cells (Fig. 20-22) can produce about...Ch. 20 - Prob. 61PCh. 20 - It has been suggested that a heat engine could be...Ch. 20 - A heat engine takes a diatomic gas around the...Ch. 20 - A 126.5-g insulated aluminum cup at 18.00C is...Ch. 20 - (a) At a steam power plant, steam engines work in...Ch. 20 - (II) Refrigeration units can be rated in tons. A...Ch. 20 - Prob. 67GPCh. 20 - (a) What is the coefficient of performance of an...Ch. 20 - The operation of a certain heat engine takes an...Ch. 20 - A car engine whose output power is 155 hp operates...Ch. 20 - Suppose a power plant delivers energy at 850 MW...Ch. 20 - 1.00 mole of an ideal monatomic gas at STP first...Ch. 20 - Two 1100-kg cars are traveling 75 km/h in opposite...Ch. 20 - Metabolizing 1.0 kg of fat results in about 3.7 ...Ch. 20 - A cooling unit for a new freezer has an inner...Ch. 20 - Prob. 76GPCh. 20 - The Stirling cycle shown in Fig 20-27, is useful...Ch. 20 - A gas turbine operates under the Brayton cycle,...Ch. 20 - Thermodynamic processes can be represented not...Ch. 20 - An aluminum can, with negligible heat capacity, is...Ch. 20 - Prob. 81GPCh. 20 - A bowl contains a large number of red, orange, and...
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- If a gas is compressed isothermally, which of the following statements is true? (a) Energy is transferred into the gas by heat. (b) No work is done on the gas. (c) The temperature of the gas increases. (d) The internal energy of the gas remains constant. (e) None of those statements is true.arrow_forwardYou have a particular interest in automobile engines, so you have secured a co-op position at an automobile company while you attend school. Your supervisor is helping you to learn about the operation of an internal combustion engine. She gives you the following assignment, related to a simulation of a new engine she is designing. A gas, beginning at PA = 1.00 atm, VA = 0.500 L, and TA = 27.0C, is compressed from point A on the PV diagram in Figure P19.31 (page 530) to point B. This represents the compression stroke in a fourcycle gasoline engine. At that point, 132 J of energy is delivered to the gas at constant volume, taking the gas to point C. This represents the transformation of potential energy in the gasoline to internal energy when the spark plug fires. Your supervisor tells you that the internal energy of a gas is proportional to temperature (as we shall find in Chapter 20), the internal energy of the gas at point A is 200 J, and she wants to know what the temperature of the gas is at point C. Figure P19.31arrow_forwardAnswer the following question in an essay form. Write the essay with at least 3 paragraphs. Can you cool a kitchen by leaving the refrigerator door open?arrow_forward
- A “solar cooker” consists of a curved reflecting mirror that focuses sunlight onto the object to be heated (Fig. P11.69). The solar power per unit area reaching the Earth at the location of a 0.50-m-diameter solar cooker is 600. W/m2. Assuming 50% of the incident energy is converted to thermal energy, how long would it take to boil away 1.0 L of water initially at 20.°C? (Neglect the specific heat of the container.)arrow_forwardIf I add 11664 J of energy to an ideal gas inside a balloon, causing the internal energy to increase by 7278 J, how much work is done on the environment by the gas as the balloon expands?arrow_forwardIf you mix food in a blender, the electric motor does work on the system, which consists of the food inside the container. This work can noticeably warm up the food. Suppose the blender motor runs at a power of 250 W for 40 s. During this time, 2000 J of heat flow from the now-warmer food to its cooler surroundings. Match the answers with questions. (Hint: Example 11.12) v W- work done on the system (food) A. 2000 J v Q- Heat into or out of the system (food) B. 8000 J v AEth - Change in thermal energy of the system (food) C. OJ D. -10,000 J E. -8000 J F. -2000 J G. 10,000 Jarrow_forward
- During a chemistry lab, you take a 0.4 kg sample of ice and put it in a beaker with a thermometer. You then place the beaker with the ice on 0 the temperature of the ice is -18 = a hot plate, and turn on the hot plate. This hot plate adds heat to the ice at a rate of 330 W. At time t °C. Because of the large heat capacity of water and ice, you may assume in this problem that all the heat goes into the sample of ice, and that we can ignore the amount of heat going into the beaker and thermometer. Also assume no heat escapes from the system. Some useful values: ● Specific heat of water: C = Specific heat of ice: Ci = 2100 J/kg K • Latent heat of fusion: L = 334 000 J/kg ● 4200 J/kg K = 1a) At what time does the ice reach a temperature of -3.5°C? answer= units? 1b) At what time has all the ice melted? answer= units? Check your answer Check your answer 1c) After the ice has completely melted, we're left with 0.4 kg of water. Check your answer answer= units? not yet solved not yet solved…arrow_forwardExplain why you can’t cool down your kitchen by leaving your refrigerator or freezer door open with your refrigerator plugged in for an extended period of time.arrow_forwardThe heat capacity of air at room temperature and pressure is approximately 21 J×mol-1×K-1. a) How much energy is required to raise the temperature of a room dimensions 5.5 m x 6.5 m x 3.0 m by 10°C from room temperature (298.15 K) assuming ideal behavior? b) How long will it take a heater rated at 1.5 kW to achieve that increase if 1 W = 1 J×s-1 (assuming no loss)?arrow_forward
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