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physics
college physics a strategic approach 2nd
College Physics Essentials Electricity And Magnetism Optics Modern Physics Volume Two 8th Edition Jerry D. Wilson, Anthony J. Buffa, Bo Lou - Solutions
13. You can often hear people talking from around a corner of a building. This is due primarily to (a) reflection,(b) refraction, (c) interference, (d) diffraction.
12. When two identical waves of the same wavelength and amplitude A overlap in phase, the amplitude of the resulting wave is (a) A, (b) 2A, (c) 3A, (d) 4A.
11. When two waves overlap, the resultant waveform is determined by (a) reflection, (b) refraction, (c) diffraction,(d) superposition.
10. A string wave is an example of what type of wave?(a) transverse, (b) longitudinal, (c) compressional,(d) none of these.
9. For a longitudinal wave, the direction between the wave velocity and medium particle oscillation is(a) 90°, (b) 0°, (c) 45°, (d) none of these.
8. Wave motion in a medium involves (a) the propagation of a disturbance, (b) inter-particle interactions,(c) the transfer of energy, (d) all of the preceding.
7. This equation describes the SHM of an object:y = Asin(2πt/T). Its position (y) three-quarters of the period after the motion starts is (a) +A, (b) −A,(c) A/2, (d) 0.
6. Given the SHM equation of motion: y = Asin[200 πt].The frequency of this oscillation is (a) 50 Hz,(b) 100 Hz, (c) 200 Hz, (d) 200π Hz.
5. The equation of motion for an object in SHM (a) is a sine or cosine function, (b) is a tangent or cotangent function, (c) could be any mathematical function,(d) none of these.
4. When an object in horizontal SHM is at its equilibrium position, the kinetic energy of the system is(a) zero, (b) maximum, (c) half its maximum, (d) none of the preceding.
3. If the frequency of a system in SHM is doubled, its period becomes (a) doubled, (b) halved, (c) four times larger, (d) one-quarter as large.
2. The maximum kinetic energy of a mass-spring system in SHM is equal to (a) A, (b) A2, (c) kA, (d) kA2/2.
1. For an object in SHM, the net force on it and its displacement from equilibrium are (a) in the same direction,(b) opposite in direction, (c) perpendicular,(d) none of the preceding.
57. •• Because of limitations on materials, the maximum temperature of the superheated steam used in a turbine for the generation of electricity is about 540 °C.(a) If the steam condenser operates at 20 °C, what is the maximum Carnot efficiency of a steam turbine generator? (b) The actual
56. •• The autoignition temperature of a fuel is defined as the temperature at which a fuel-air mixture would self-explode and ignite. Thus, it sets an upper limit on the temperature of the hot reservoir in an automobile engine. The autoignition temperatures for commonly available gasoline and
55. IE •• A Carnot engine operating between reservoirs at 27 °C and 227 °C does 1500 J of work in each cycle.(a) The change in entropy for the engine for each cycle is (1) negative, (2) zero, (3) positive. Why? (b) What is the heat input of the engine?
54. •• A heat engine operates at a thermal efficiency that is 45% of the Carnot efficiency. If the temperatures of the high-temperature and low-temperature reservoirs are 400 °C and 50 °C, respectively, what are the Carnot efficiency and the thermal efficiency of the engine?
53. •• An inventor claims to have developed a heat engine that, each cycle, takes in 5.0 × 105 J of heat from a hightemperature reservoir at 400 °C and exhausts 2.0 × 105 J to the surroundings at 125 °C. Would you invest your money in the production of this engine? Explain.
52. •• An inventor claims to have created a heat engine that produces 10.0 kW of power for a 15.0-kW heat input while operating between reservoirs at 27 °C and 427 °C. (a) Is this claim valid? (b) To produce 10.0 kW of power, what is the minimum heat input required?
51. IE •• A Carnot engine takes in heat from a reservoir at 350 °C and has an efficiency of 35%. The exhaust temperature has not changed, and the efficiency is increased to 40%. (a) The temperature of the hot reservoir is (1) lower than, (2) equal to, (3) higher than 350 °C. Explain. (b) What
50. •• A Carnot engine takes 2.7 × 104 J of heat per cycle from a high-temperature reservoir at 320 °C and exhausts some of it to a low-temperature reservoir at 120 °C. How much net work is done by the engine per cycle?
49. •• A Carnot engine with an efficiency of 40% operates with a low-temperature reservoir at 40 °C and exhausts 1200 J of heat each cycle. What are (a) the heat input per cycle and (b) the Celsius temperature of the high-temperature reservoir?
48. • An engineer wants to run a heat engine with an efficiency of 40% between a high-temperature reservoir at 300 °C and a low-temperature reservoir.What is the maximum Celsius temperature of the low-temperature reservoir?
47. • What is the Celsius temperature of the hot reservoir of a Carnot engine that is 32% efficient and has a 20 °C cold reservoir?
46. • It has been proposed that temperature differences in the ocean could be used to run a heat engine to generate electricity. In tropical regions, the water temperature is about 25 °C at the surface and about 5 °C at very deep depths. (a) What would be the maximum theoretical efficiency of
45. • A steam engine operates between 100 °C and 20 °C.What is the Carnot efficiency of the ideal engine that operates between these temperatures?
44. • A Carnot engine has an efficiency of 35% and takes in heat from a high-temperature reservoir at 178 °C.What is the Celsius temperature of the engine’s lowtemperature reservoir?
43. ••• A coal-fired power plant produces 900 MW of electric power and operates at a thermal efficiency of 25% (a) What is the input heat rate from the burning coal? (b) What is the rate of heat discharge from the plant? (c) Water at 15 °C from a nearby river is used to cool the discharged
42. •• A steam engine has a thermal efficiency of 15.0%. If its heat input for each cycle is supplied by the condensation of 8.00 kg of steam at 100 °C (a) what is the net work output per cycle, and (b) how much heat is lost to the surroundings in each cycle?
41. •• A heat pump removes 2.2 × 103 J of heat from the outdoors and delivers 4.3 × 103 J of heat to the inside of a house each cycle. (a) How much work is required per cycle? (b) What is the COP of this pump?
40. •• An air conditioner has a COP of 2.75. What is the power rating of the unit if it is to remove 1.00 × 107 J of heat from a house interior in 20 min?
39. •• A refrigerator with a COP of 2.2 removes 4.2 × 105 J of heat from its interior each cycle. (a) How much heat is exhausted each cycle? (b) What is the total work input in joules for 10 cycles?
38. •• When running, a refrigerator exhausts heat to the kitchen at a rate of 10 kW when the required input work is at a rate of 3.0 kW. (a) At what rate is heat removed from its cold interior? (b) What is the COP of the refrigerator?
37. IE •• An engineer redesigns a heat engine and improves its thermal efficiency from 20% to 25%. (a) Must the ratio of the heat input to heat output (1) increase, (2)remain the same, or (3) decrease? Explain. (b) What is the engine’s change in Qh/Qc after the redesign is implemented?
36. IE •• A steam engine is to have its thermal efficiency improved from 8.00% to 10.0% while continuing to produce 4500 J of useful work per cycle. (a) Must the ratio of the heat output to heat input (1) increase,(2) remain the same, or (3) decrease? Why? (b) What is the change in Qc/Qh if
35. •• A gasoline engine burns fuel that releases 3.3 × 108 J of heat per hour. (a) What is the energy input during a 2.0 h period? (b) If the engine delivers 25 kW of power during this time, what is its thermal efficiency?
34. IE • The heat output of an engine is 1.75 × 103 J per cycle, and the net work out is 4.0 × 103 J per cycle. (a) The heat input is (1) less than 44.0 × 103 J,(2) between 4.0 × 103 J and 7.5 × 103 J, (3) greater than 7.5 × 103 J. Explain. (b) What is the heat input and thermal efficiency
33. • A heat engine with a thermal efficiency of 15.0%absorbs 1.75 × 105 J of heat from the hot reservoir. How much heat is lost per each cycle?
32. • A heat engine with a thermal efficiency of 20% does 500 J of net work each cycle. How much heat per cycle is lost to the low-temperature reservoir?
31. • A gasoline engine has a thermal efficiency of 28%. If the engine absorbs 2000 J of heat per cycle, (a) what is the net work output per cycle? (b) How much heat is exhausted per cycle?
30. • If an engine does 200 J of net work and exhausts 800 J of heat per cycle, what is its efficiency?
29. • If an engine does 400 J of net work each cycle while absorbing 2000 J of heat each cycle, what is its efficiency?
28. IE •• Two large heat reservoirs at temperatures 200 °C and 60 °C, respectively, are brought into thermal contact, and 1.5 × 103 J of heat spontaneously flows from one to the other with no significant temperature change. (a) The change in the entropy of the tworeservoir system is (1)
27. IE •• A perfectly isolated system consists of two large thermal reservoirs at constant temperatures of 100 °C and 0 °C. Assume the reservoirs make contact and 1000 J of heat flowed from the cold reservoir to the hot reservoir spontaneously with no appreciable reservoir temperature
26. •• In the winter, heat from a house with an inside temperature of 18 °C leaks out at a rate of 2.0 × 104 J/s. The outside temperature is 0 °C. (a) What is the change in entropy per second of the house? (b) What is the total change in entropy per second of the house-outside system?
25. IE •• A quantity of an ideal gas undergoes an isothermal expansion at 20 °C and does 3.0 × 103 J of work on its surroundings in the process. (a) Will the entropy of the gas (1) increase, (2) remain the same, or (3) decrease?Explain. (b) What is the change in the entropy of the gas?
24. IE •• One mole of an ideal gas undergoes an isothermal compression at 0 °C, and 7.5 × 103 J of work is done in compressing the gas. (a) Will the entropy of the gas(1) increase, (2) remain the same, or (3) decrease? Why?(b) What is the change in entropy of the gas?
23. •• In an isothermal expansion at 27 °C, an ideal gas does 60 J of work. What is the change in entropy of the gas?
22. • During a liquid-to-solid phase change of a substance, its change in entropy is −4.19 × 103 J/K. If 1.67 × 106 J of heat is removed in the process, what is the freezing point of this substance in degrees Celsius?
21. IE • A process involves 1.0 kg of steam condensing to water at 100 °C. (a) The change in entropy of the steam (water) is (1) positive, (2) zero, (3) negative. Why?(b) Compute the change in entropy of the steam (water)?
19. • What is the change in entropy of mercury vapor(Lv = 2.7 × 105 J/kg) when 0.50 kg of it condenses to a liquid at its boiling point of 357 °C?20. IE • 2.0 kg of ice melts completely into liquid water at 0 °C. (a) The change in entropy of the ice (water) in this process is (1) positive,
16. IE ••• The temperature of 2.0 mol of ideal gas is increased from 150 °C to 250 °C by two different processes.In process A, 2500 J of heat is added to the gas;in B, 3000 J of heat is added. (a) In which case is more work done: (1) A, (2) B, or (3) the same amount of work is done during
15. •• An ideal gas sample expands isothermally by tripling its volume while doing 5.0 × 104 J of work at 40 °C. (a) How many moles of gas are in the sample?(b) Was heat added to or removed from the sample, and how much?
14. •• A monatomic ideal gas (γ = 1.67) is compressed adiabatically from a pressure of 1.00 × 105 Pa and volume of 240 L to a volume of 40.0 L. (a) What is the final pressure of the gas? (b) How much work is done on the gas?
13. IE •• 2.0 mol of an ideal gas expands isothermally from a volume of 20 L to 40 L at 20 °C. (a) The work done by the gas is (1) positive, (2) negative, (3) zero.Explain. (b) What is the magnitude of the work?
12. IE •• An ideal gas is enclosed in a cylindrical piston with a 12.0-cm radius. Heat is slowly added to the gas while the pressure is maintained at 1.00 atm. During the process, the piston moves 6.00 cm. (a) This is an(1) isothermal, (2) isobaric, (3) adiabatic process.Explain. (b) If the
11. •• Suppose that after the final process in Figure 12.24, the pressure of the gas is first decreased isometrically from 1.0 × 105 Pa to 0.70 × 105 Pa, and then compressed isobarically from 1.0 m3 to 0.80 m3. What is the overall net work done now, from start to the new finish?
8. •• An Olympic weight lifter lifts 145 kg a vertical distance of 2.1 m. When he does so, 6.0 × 104 J of heat is transferred to air through perspiration. Does he gain or lose internal energy, and how much?
7. •• An ideal gas is under an initial pressure of 2.45 × 104 Pa and occupies a volume of 0.20 m3. The slow addition of 8.4 × 103 J of heat to this gas causes it to expand isobarically to a volume of 0.40 m3. (a) How much work is done by the gas? (b) Does the thermal energy of the gas change?
6. IE • An ideal gas expands from 1.0 m3 to 3.0 m3 at atmospheric pressure while absorbing 5.0 × 105 J of heat. (a) The temperature of the gas (1) increases,(2) stays the same, (3) decreases. Explain. (b) What is the change in thermal energy of the gas?
5. IE • While doing 500 J of work, an ideal gas expands adiabatically to 1.5 times its initial volume. (a) The temperature of the gas (1) increases, (2) remains the same, (3) decreases. Why? (b) What is the change in the thermal energy of the gas?
4. • An ideal gas goes through a thermodynamic process in which 500 J of work is done on the gas and the gas loses 300 J of heat. What is the change in thermal energy of the gas?
3. IE • A quantity of ideal gas goes through an isothermal process and does 400 J of net work. (a) The thermal energy of the gas is (1) higher than, (2) the same as,(3) less than when it started. Why? (b) Is heat added to or removed from the system, and how much is involved?
2. IE • A rigid container contains 1.0 mol of an ideal gas that slowly receives 2.0 × 104 J of heat. (a) The work done by the gas is (1) positive, (2) zero, (3) negative.Why? (b) What is the change in the thermal energy of the gas?
1. • When playing in a tennis match, you lose 6.5 × 105 J of heat, and your internal energy decreases by 1.2 × 106 J. How much work did you do in the match?
24. Carnot engine A operates at a higher hot reservoir temperature than Carnot engine B. Will engine A necessarily have a higher Carnot efficiency? Explain.
23. If you have the choice of running your heat engine between either of the following two sets of temperatures for the cold and hot reservoirs, which would you choose, and why: between 100 °C and 300 °C or between 50 °C and 250 °C? Explain.
22. Diesel engines are more efficient than gasoline engines.Which type of engine would you expect to run hotter?Why?
21. The maximum efficiency of a heat engine is less than 1(
20. The heat output of a thermal pump is greater than the energy used to operate the pump. Does this device violate the first law of thermodynamics? Explain.
19. If heat engine A absorbs more heat than heat engine B from a hot reservoir, will engine A necessarily do more net work than engine B? Explain your reasoning.
18. Lord Kelvin’s statement of the second law of thermodynamics as applied to heat engines (“No heat engine operating in a cycle can convert its heat input completely to work”) refers to their operation in a cycle.Why is the phrase “in a cycle” included?
17. What is the net change in pressure and thermal energy of a cyclic ideal gas heat engine at the end a complete cycle?
16. A student tries to cool his dormitory room by opening the refrigerator door. Will that work? Explain.
15. The Sun formed into a more ordered system by gravitational collapse of a huge gas cloud about five billion years ago. How could this apparent entropy decrease happen if natural processes are supposed to result in an entropy increase? Explain.
14. A student challenges the second law of thermodynamics by saying that entropy does not have to increase in all situations, such as when water freezes to ice. Is this challenge valid? Why or why not?
13. When a quantity of hot water is mixed with a quantity of cold water, the combined system comes to thermal equilibrium at some intermediate temperature. How does the entropy of each liquid change? The system?
12. Does the entropy of each of the following objects increase or decrease? (a) Ice as it melts; (b) water vapor as it condenses; (c) water as it is heated on a stove;(d) food as it is cooled in a refrigerator.
11. Heat is converted to mechanical energy in many applications, such as car engines. Is this a violation of the second law of thermodynamics? Explain.
10. Using the kinetic theory (microscopic) picture of an ideal gas, explain the decrease in thermal energy that occurs during an adiabatic expansion.
9. Using the kinetic theory (microscopic) picture of an ideal gas, explain the increase in temperature during an adiabatic compression.
8. If ideal gas sample A receives more heat than ideal gas sample B, will A necessarily experience a higher increase in thermal energy? Explain.
6. In an isobaric expansion, an ideal gas sample can do work on the environment, but its temperature also increases. How can this be? Explain.
5. In an adiabatic process, there is no heat exchange between the system and the environment, but the temperature of the ideal gas changes. How can this be?Explain.
4. Discuss heat, work done by you, and the change in internal energy of your body when you shovel snow.
2. On a p-V diagram, sketch a cyclic process that consists of an isothermal expansion followed by an isobaric compression and ending with an isometric process.
1. On a p-V diagram, sketch an isobaric process for an ideal gas that results in a temperature drop.
19. For a given amount of heat removed from its interior Qc, which refrigerator has the highest COP?(a) Qh = 1.1 Qc, (b) Qh = 1.5 Qc, (c) Qh = 2.5 Qc, or(d) Qh = 5.5 Qc?
18. For a heat engine that operates between two reservoirs with temperatures Tc and Th, the Carnot efficiency is the (a) highest possible, (b) lowest possible,(c) an average value, or (d) none of the preceding.
17. Which of the following temperature reservoir relationships would yield the lowest efficiency for a Carnot engine? (a) Tc = 0.15Th, (b) Tc = 0.25Th, (c) Tc = 0.50Th, or (d) Tc = 0.90Th?
16. The Carnot cycle consists of (a) two isobaric and two isothermal processes, (b) two isometric and two adiabatic processes, (c) two adiabatic and two isothermal processes, or (d) any four processes that return the system to its initial state.
15. Which of the following is the determining factor in the thermal efficiency of a heat engine?(a) Qc × Qh, (b) Qc / Qh, (c) Qh − Qc, or (d) Qh + Qc?
14. A thermal pump (a) is rated by thermal efficiency,(b) requires work input, (c) has Qh = Qc, (d) must have a COP < 1.
13. For a cyclic heat engine: (a) ε = 1, (b) Qh = Wnet,(c) ΔEth = Wnet, (d) Qh > Qc.
12. When the first law of thermodynamics is applied to a heat engine, the result is: (a) Wnet = Qh + Qc,(b) Wnet = Qh − Qc, (c) Wnet = Qc − Qh, (d) Qc = 0.
11. An ideal gas is compressed isothermally. The change in entropy of the gas for this process is (a) positive,(b) negative, (c) zero, (d) none of the preceding.
10. Which one of the following statements is a violation of the second law of thermodynamics: (a) heat flows naturally from hot to cold, (b) heat can be completely converted to mechanical work, (c) the entropy of the universe can never decrease?
9. For which type of thermodynamic process is the change in entropy of an ideal gas zero: (a) isothermal,(b) isobaric, (c) isometric, or (d) none of the preceding?
8. During any natural process, the overall change in the entropy of the system involved could not be(a) negative, (b) zero, (c) positive.
7. When an ideal gas is compressed isobarically, (a) its thermal energy increases, (b) it does negative work on the environment, (c) its pressure increases.
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