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Unformatted text preview: HW Set IX page 1 of 6 PHYSICS 1401 (1) homework solutions 19-24 In a certain experiment, a small ra-dioactive source must move at selected, ex-tremely slow speeds. This motion is accom-plished 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 effi-ciency of the overall system is 20% (that is, 80% of the incident solar energy is lost from the sys-tem). What collector area is necessary to raise the temperature of 200 L of water in the tank from 20°C to 40°C in 1.0 h when the intensity of incident sunlight is 700 W/m 2 ? ?...