First slide

Radiation

Question

A body cools from 70⁰C to 50⁰C in 5 minutes. Temperature of surroundings is 20⁰ C. Its temperature after next 10 minutes is

Easy

A

25⁰ C
B

35⁰C
C

30⁰C
D

45⁰C

Solution

According Newton's Law of cooling $\large \frac {-d\theta}{dt}\propto (\theta -\theta_0)$ when the surface temperature of the body is assumed to fall linearly, θ is taken as the average surface temperature.
$\large \frac {70-50}{5}=k\left ( \frac {70+50}{2}-20 \right )$
$\large k=\frac {1}{10};\;\frac {50-\theta}{10}=\frac {1}{10}\left ( \frac {50+\theta}{2}-20 \right );\;\theta=30^0C$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App