Two students X and Y have to do their experiment on plotting the temperature-time graph for a hot body as it cools to room temperature. They do their experiments in the same lab, using completely identical apparatus, take equal amounts of tap water heated up to the same temperature, start their observations simultaneously and note the temperature values at identically spaced intervals of time. Their temperature-time graphs, plotted on a given graph paper, with the same give choices of scales along the axis, are however, as shown :

The following could be the reason for this difference :
(A) Use of an overhead fan by student X.
(B) Use of an overhead fan by student Y.
(C) Less frequent stirring of water by student X.
(D) Less frequent stirring of water by student Y.
The most likely reason is :
(1) A
(2) B
(3) C
(4) D

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Solution

As we can see from the graph made by student X, the body cools down fast in comparison with the graph made by student Y. The body cools down slowly in the case of student B. As both students performed the same experiment under the same laboratory, the only factor of faster cooling in the case of student X can be the use of an overhead fan. So due to the use of an overhead fan by student X, the temperature of the body falls faster, it cools down quicker.

Hence, the correct answer is option 1.

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