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recitation12-ThermoFluids-solutions

# Theentropylostbytheicecubeisequaltotheentropygainedbyt

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Unformatted text preview: refrigerator has a coefficient of performance equal to 4.2. How much work must be done on the refrigerator in order to remove 250 J of heat from the interior? a) 60 J b) 120 J c) 250 J d) 480 J e) 1050 J 9. A Carnot engine operates between a high temperature reservoir at 435 K and a river with water at 280 K. If it absorbs 3700 J of heat each cycle, how much work per cycle does it perform? a) 1318 J b) 2382 J c) 1449 J d) 2251 J Ten mol of a monatomic ideal gas is taken around the cycle shown in the figure below in the direction shown. The path for process c‐>a is a straight line in the pV‐diagram. Calculate Q, W and U for each process. Water flows in the horizontal pipe shown in the figure. At point A the area is 25.0 cm2 and the speed of the water is 2.00 m/s. At B the area is 16.0 cm2. The fluid in the manometer is mercury, which has a density of 13,600 kg/m3. We can treat water as an ideal fluid having a density of 1000 kg/m3. What is the manometer reading, h? 5. The second law of thermodynamics leads us to conclude that a) the total energy of the universe is constant. b) disorder in the universe is increasing with the passage of time. c) it is theoretically impossible to convert work into heat with 100% efficiency. d) the total energy in the universe is increasing with time. e) the total energy in the universe is decreasing with time. 6. An ice cube at 0°C is placed in a very large bathtub filled with water at 30°C and allowed to melt, causing no appreciable change in the temperature of the bath water. Which one of the following statements is true? a) The entropy gained by the ice cube is equal to the entropy lost by the water. b) The entropy lost by the ice cube is equal to the entropy gained by the water. c) The net entropy change of the system (ice plus water) is zero because no heat was added to the system. d) The entropy of the system (ice plus water) increases because the process is irreversible. e) The entropy of the water does not change because its temperature did not change. 7. A heat engine with an efficiency of 30.0% performs 2500 J of work. How much heat is discharged to the lower temperature reservoir? a) 5830 J b) 8330 J c) 750 J d) 1350 J e) 7080 J 8. A refrigerator has a coefficient of performance equal to 4.2. How much work must be done on the refrigerator in order to remove 250 J of heat from the interior? a) 60 J b) 120 J c) 250 J d) 480 J e) 1050 J 9. A Carnot engine operates between a high temperature reservoir at 435 K and a river with water at 280 K. If it absorbs 3700 J of heat each cycle, how much work per cycle does it perform? a) 1318 J b) 2382 J c) 1449 J d) 2251 J...
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