A) 5 J/s
B) 15 J/s
C) 100 J/s
D) 115 J/s
Correct Answer: D
Solution :
Rate of cooling (here it is rate of loss of heat) \[\frac{dQ}{dt}=(mc+W)\frac{d\theta }{dt}=({{m}_{l}}{{c}_{l}}+{{m}_{c}}{{c}_{c}})\frac{d\theta }{dt}\] Þ \[\frac{dQ}{dt}=(0.5\times 2400+0.2\times 900)\left( \frac{60-55}{60} \right)\]\[=115\ \frac{J}{\sec }\].
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