Physics Essay

680 WordsMay 17, 20153 Pages
PHYSICS 2, CHAPTER 5 ADDITIONAL PROBLEMS 1. A Carnot engine has an efficiency of.22.0% . It operates between constant-temperature reservoirs differing in temperature by 75.0 Co. What is the temperature of the (a) lower temperature and (b) higher-temperature reservoir? ANSWER: (a) 266 K; (b) 341K 2. A Carnot engine operates between 235oC and 115oC, absorbing 6.30 ( 104 J per cycle at the higher temperature. (a) What is the efficiency of the engine? (b) How much work per cycle is this engine capable of performing? ANSWER: a) 23.6%; (b) 1.49 ( 104 J 3. Figure 1 shows a reversible cycle through which 1.00 mol of a monatomic ideal gas is taken. Volume Vc = 8.00Vb. Process bc is an adiabatic expansion, with pb = 10.0 atm and Vb = 1.00 ( 10-3 m3. For the cycle, find (a) the energy added to the gas as heat, (b) the energy leaving the gas as heat, (c) the net work done by the gas, and (d) the efficiency of the cycle. ANSWER: (a) 1.47 kJ; (b) 554 J; (c) 918 J; (d) 62.4% 4. Figure 2 shows a reversible cycle through which 1.00 mol of a monatomic ideal gas is taken. Assume that p = 2po , V = 2Vo, po = 1.01 ( 105 Pa, and Vo = 0.0225 m3. Calculate (a) the work done during the cycle, (b) the energy added as heat during stroke abc, and (c) the efficiency of the cycle. (d) What is the efficiency of a Carnot engine operating between the highest and lowest temperatures that occur in the cycle? (e) Is this greater than or less than the efficiency calculated in (c)? ANSWER: (a) 2.21 kJ; (b) 14.8 kJ; (c) 1,5.4%; (d) 7 5.0%;(e) greater 5. A Carnot air conditioner takes energy from the thermal energy of a room at 70oF and transfers it as heat to the outdoors, which is at 96oF, For each joule of electric energy required to operate the air conditioner, how many joules are removed from the room? ANSWER: 37.20 J 6. A heat pump is used to heat a building. The

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