A solar heated house loses about 7.4 × 10⁷ cal through its outer surfaces on a typical 24-hour winter day.What mass of storage rock is needed to provide this amount of heat if it is brought up to initial temperature of 62°C by the solar collectors,and the house is maintained at 20°C? (Specific heat of rock is 0.21 cal/g · °C. ) A) 160 kg B) 1200 kg C) 6100 kg D) 8400 kg

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Quizplus · Accepted Answer

To find the mass of the storage rock, use the formula Q = mcΔT, where Q is the heat lost (7.4 × 10^7 cal), m is the mass, c is the specific heat (0.21 cal/g°C), and ΔT is the temperature change (62°C - 20°C = 42°C). Solving for m gives m = Q / (cΔT) = 7.4 × 10^7 cal / (0.21 cal/g°C × 42°C) = 8400 kg.

A Solar Heated House Loses About 7