A body cools from 50.0^o C to 49.9^o C in 5 ;s. How long will it … - Vidyadip

MCQ

A body cools from ${50.0^o}C$ to ${49.9^o}C$ in $5\;s$. How long will it take to cool from ${40.0^o}C$ to ${39.9^o}C$? Assume the temperature of surroundings to be ${30.0^o}C$ and Newton's law of cooling to be valid ....... $\sec$

A
$2.5 $
✓
$10 $
C
$20$
D
$5$

✓

Answer

Correct option: B.

$10 $

b
(b) $\frac{{50 - 49.9}}{5} = K\,\left( {\frac{{50 + 49.9}}{2} - 30} \right)$…..$(i)$
$\frac{{40 - 39.9}}{t} = K\,\left[ {\frac{{40 + 39.9}}{2} - 30} \right]$…..$(ii)$
from equations $(i)$ and $(ii)$

we get $t ≈ 10 sec$ .

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