A body cools from {60^o}C to {50^o}C in 10 minutes. If room temperature is {25^o}C and assuming Newt

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10-2.Transmission of Heat

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A body cools from ${60^o}C$ to ${50^o}C$ in $10$ minutes. If the room temperature is ${25^o}C$ and assuming Newton's law of cooling to hold good, the temperature of the body at the end of the next $10$ minutes will be ......... $^oC$

A

$38.5$

B

$40$

C

$42.85$

D

$45$

Solution

(c) $\frac{{60 – 50}}{{10}} = K\left( {\frac{{60 + 50}}{2} – 25} \right)$….$.(i)$

$\frac{{50 – \theta }}{{10}} = K\left[ {\frac{{50 + \theta }}{2} – 25} \right]$…..$(ii)$

On dividing, we get $\frac{{10}}{{50 – \theta }} = \frac{{60}}{\theta } $

$\Rightarrow \theta = {42.85^o}C$

Standard 11

Physics

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