According to Newton's Law of Cooling, the rate of cooling of a body is directly proportional to the temperature difference between the body and its surroundings. As the tea cools, its temperature decreases, and thus the temperature difference between the tea and the surrounding environment decreases. This smaller temperature difference results in a slower rate of cooling. Therefore, cooling through the same temperature range (10°C) at a lower average temperature (65°C to 55°C) will take longer than cooling through the same range at a higher average temperature (85°C to 75°C), assuming the surrounding temperature remains constant.
If the time taken by a cup of tea to cool from 85°C to 75°C is 1 minute, then the time taken by it to cool from 65°C to 55°C is
Asked in TNPSC CS Prelims 2015 · Topic: Heat and Thermodynamics (Modes of Heat Transfer (Conduction, Convection, Radiation))
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