A) 5 min
B) lesser than 5 min
C) greater than 5 min
D) lesser or greater than 5 min depending upon the density of the liquid
Correct Answer: C
Solution :
According to Newton's law of cooling, Rate of cooling \[\propto \] mean temperature difference \[\frac{d{{Q}_{1}}}{dt}=k\left( \frac{70+60}{2}-{{\theta }_{0}} \right)=(65-{{\theta }_{0}})\] \[\frac{d{{Q}_{2}}}{dt}=k\left( \frac{60+50}{2}-{{\theta }_{0}} \right)=(55-{{\theta }_{0}})\] As \[\frac{d{{Q}_{2}}}{dt}<\frac{d{{Q}_{1}}}{dt}\] As, rate of cooling is decreased, therefore liquid will take more than 5 min to cool from \[{{60}^{o}}C\]to \[{{50}^{o}}C\].
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