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Day 16, Physics 131, 2015
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Asked about her school year, she replied: “Opa, it was not hard
Asked about her school year, she replied: “Opa, it was not hard. It is much easier when you read the [text]book.” Katherine Alice Keller, June 26, 2015
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HW Problem 17-7 In the morning, when the temperature is
286 K, a bicyclist finds that the absolute pressure in his tires in 501 kPa. That afternoon he find that the pressure in the tires has increased to 554 kPa. ? Ignoring expansion of the tires, find the afternoon temperature. ??
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HW Problem 17-18 The air inside a hot-air balloon has an average temperature of 79.2oC. The outside air has a temperature of 20.3oC. ? What is the ratio of the density of air in the balloon to the density of air in the surrounding atmosphere ??
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HW Problem 17-28 Three moles of oxygen gas (3.0 mol of O2) are placed in a portable container with a volume of m3. If the temperature of the gas is 295oC, find ? (a) the pressure of the gas ?? ? (b) the average kinetic energy of an oxygen molecule ? Suppose the volume of the gas is doubled, while the temperature and number of moles are held constant. ? By what factor do your answers in parts (a) and (b) change??
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HW Problem 17-40 The deepest place in all the oceans is the Marianas Trench, were the depth is 10.9 km and the pressure is 1.1 x 108 Pa. ? If a copper ball 15.0 cm in diameter is taken to the bottom of the trench, by how much does its volume decrease ??
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HW Problem 17-52 See the phase diagram for CO2.
? (a) What is the phase of CO2 at T = 20oC and P = 500 kPa ? ? (b) What is the phase of CO2 at T = -80oC and P = 120 kPa ? ? (c) What is the minimum pressure required to keep CO2 in the liquid phase at 20oC ?
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HW Problem 17-71 A 48-g block of copper at -12oC is added to 110 g of water in a 75-g aluminum cup. The cup and the water have an initial temperature of 4.1oC. ? (a) find the equilibrium temperature of the cup and its contents ? ? (b) What mass of ice, if any, is present when the system reaches equilibrium ?
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HW Problem 17-66 When you go out to your car one cold winter morning you discover a 0.58-cm-thick layer of ice on the windshield. The windshield has an area of 1.5 m2. The temperature of the ice is -2.0oC. The density of the ice is 917 kg/m3. ? How much heat is required to melt all of the ice ??
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HW Problem 18-52 During each cycle a reversible engine absorbs 2500 J of heat from a high-temperature reservoir and performs 2200 J of work. (a) What is the efficiency of this engine ? (b) How much heat is exhausted to the low-temperature reservoir during each cycle ? (c) What is the ratio, Th/Tc of the two reservoir temperatures?
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HW Problem 18-58 To keep a room at a comfortable 21.0oC, a Carnot heat pump does 345 J of work and supplies it with 3240 J of heat. ? (a) How much heat is removed from the outside air by the heat pump ? ? (b) What is the temperature of the outside air ?
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