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A house is at 20°C on a winter night when the outside temperature is a steady −15°C. The house’s heat capacity is 6.5 MJ/K and its thermal resistance is 6.67 mK/W. If the furnace suddenly fails, how long will it take the house temperature to reach the freezing point? (Hint: Combine the differential forms of Equations 16.3 and 16.5 to show that the rate of temperature change is proportional to the temperature difference between the house and its surroundings. This relation is known as Newton’s low of cooling.)
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