1.

Time taken by the body to cool from 45^(@)C to 35^(@)C is

Answer»

5 min
4 min
6 min
8 min

Solution :`dT=50-40=10^(@)C,t=5` min
AVERAGE temperature `=(50+40)/(2)=45^(@)`
`:.(dT)/(dt)=-K(T-T_(c))`
`(10)/(5)=-k(45-18)`. . . (i)
`dT=45-35=10^(@)C`
Average temperature, `(45+35)/(2)=40^(@)C`
`:.(dT)/(dt)=-k[T-T_(c)]`
`(10)/(t)=-k[40-18]`. . .(ii)
DIVIDING (i) by (ii)
`t/5=(45-18)/(40-18)`
`rArrt=5xx(27)/(22)~=6` min
So correct is (c ).


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