Transmission Of Heat Question 196
Question: A body takes 5 minutes to cool from 90oC to 60oC. If the temperature of the surroundings is 20oC, the time taken by it to cool from 60oC to 30oC will be.
[RPMT 2003]
Options:
A) 5 min
B) 8 min
C) 11 min
D) 12 min
Show Answer
Answer:
Correct Answer: C
Solution:
$ \frac{90-60}{5}=k( \frac{90+60}{2}-20 ) $
Therefore $ 6=k\times 55 $
Therefore $ K=\frac{6}{55} $ And, $ \frac{60-30}{t}=\frac{6}{55}( \frac{60+30}{2}-20 ) $
Therefore t = 11 minute.
BETA
