Multiple choice

A small copper ball of 5 mm diameter at 500 K is dropped into an oil bath whose temperature is 300 K. The thermal conductivity of copper is 400 W/m.K, its density 9000 kg/m3 and its specific heat 385 J/kg.K. If the heat transfer coefficient is 250 W/m2.K and lumped analysis is assumed to be valid, the rate of fall of the temperature of the ball at the beginning of cooling will be

  1. 8.7 K/s

  2. 13.9 K/s

  3. 17.3 K/s

  4. 27.7 K/s
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C Correct answer
Explanation

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