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Set HW IX page 1 of 6 PHYSICS 1401 (1) homework solutions 19-24 In a certain experiment, a small radioactive source must move at selected, extremely slow speeds. This motion is accomplished by fastening the source to one end of an aluminum rod and heating the central section of the rod in a controlled way. If the effective heated section of the rod in Fig. 19-31 is 2.00 cm, at what constant rate must the temperature of the rod be changed if the source is to move at a constant speed of 100 nm/s? 19-42 In a solar water heater, energy from the Sun is gathered by water that circulates through tubes in a rooftop collector. The solar radiation enters the collector through a transparent cover and warms the water in the tubes; this water is pumped into a holding tank. Assume that the efficiency of the overall system is 20% (that is, 80% of the incident solar energy is lost from the system). What collector area is necessary to raise the temperature of 200 L of water in the tank from 20C to 40C in 1.0 h when the intensity of incident sunlight is 700 W/m2? HW Set IX page 2 of 6 PHYSICS 1401 (1) homework solutions 19-52 Gas within a chamber passes through the cycle shown in Fig. 19-37. Determine the energy transferred by the system as heat during process CA if the energy added as heat QAB during process AB is 20.0 J, no energy is transferred as heat during process BC, and the net work done during the cycle is 15.0 J. HW Set IX page 3 of 6 PHYSICS 1401 (1) homework solutions 19-58 If you were to walk briefly in space without a spacesuit while far from the Sun (as an astronaut does in the movie 2001), you would feel the cold of spacewhile you radiated energy, you would absorb almost none from your environment. (a) At what rate would you lose energy? (b) How much energy would you lose in 30 s? Assume that your emissivity is 0.90, and estimate other needed data in the calculations. HW Set IX page 4 of 6 PHYSICS 1401 (1) homework solutions 19-63 (a) What is the rate of energy loss in watts per square meter through a glass window 3.0 mm thick if the outside temperature is -20F and the inside temperature is +72F? (b) A storm window having the same thickness of glass is installed parallel to the first window, with an air gap of 7.5 cm between the two windows. What now is the rate of energy loss if conduction is the only important energy-loss mechanism? HW Set IX page 5 of 6 PHYSICS 1401 (1) homework solutions 20-2 Gold has a molar mass of 197 g/mol. (a) How many moles of gold are in a 2.50 g sample of pure gold? (b) How many atoms are in the sample? 20-12 A container encloses two ideal gases. Two moles of the first gas are present, with molar mass M1. The second gas has molar mass M2 = 3M1, and 0.5 mol of this gas is present. What fraction of the total pressure on the container wall is attributable to the second gas? (The kinetic theory explanation of pressure leads to the experimentally discovered law of partial pressures for a mixture of gas...


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