A vessel contains M grams of water at a certain temperature and water at certain other temperature is passed into it at a constant rate of `mg//s`. The variation of temeprature of the mixture with time is shown in Fig. The values of M and m are, respectively (the heat exhanged after a long time is 800 cal)

Options

A. (a)40 and 2
B. (b)40 and 4
C. (c)20 and 4
D. (d)20 and 2

Answer

B

Explanation

Evidently the initial temperature of the water contained in the vessel (Mg) is `80^@C` and the temperature of the water passed into it is `60^@C` as the final temperature of the mixture tends to attain a value of `60^@C`
`Mxx1(80-70)=mxx10xx1(70-60)`
or `M//m=10`
since the heat exhanged after a long time is 800 cal.
`(Mg)(1cal//(m^(@)C)(80-60^(@)C)=80cal`
or `M=40g`
`implies m=4g`