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One day in the morning, Ramesh filled up $\frac {1}{3}$ bucket of hot water from geyser, to take bath. Remaining $\frac {2}{3}$ was to be filled by cold water (at room temperature) to bring mixture to a comfortable temperature. Suddenly Ramesh had to attend to something which would take some times, say $5-10$ $\min$ before he could take bath. Now he had two options: $(1)$ fill the remaining bucket completely by cold water and then attend to the work, $(2)$ first attend tothe work and fill the remaining bucket just before taking bath. Which option do you think would have kept water warmer ? Explain.
Solution
In first option, water will be hot (warm) and convenient to bath because according to Newton's law of cooling, cooling rate proportion to temperature difference of substance and surrounding is direct and in this first option temperature difference is low hence cooling rate is also low hence water will not become very cool.
