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Q. |
A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. The density and the specific heat of the metal are 3000 kg/m3 and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m2.K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60°C is |
A. | 555 |
B. | 55.5 |
C. | 0.55 |
D. | 0.15 |
Answer» D. 0.15 |
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