A) 5 minutes
B) Lesser than 5 minutes
C) Greater than 5 minutes
D) Lesser or greater than 5 minutes depending upon the density of the liquid
Correct Answer: C
Solution :
According to Newton's law of cooling Rate of cooling µ mean temperature difference. Initially, mean temperature difference \[=\left( \frac{70+60}{2}-{{\theta }_{0}} \right)=(65-{{\theta }_{0}})\] Finally, mean temperature difference \[=\left( \frac{60+50}{2}-{{\theta }_{0}} \right)=(55-{{\theta }_{0}})\] In second case mean temperature difference decreases, so rate of fall of temperature decreases, so it takes more time to cool through the same range.
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