Transmission Of Heat Question 192
Question: The initial temperature of a body is 80°C. If its temperature falls to 64°C in 5 minutes and in 10 minutes to 52°C then the temperature of surrounding will be
[MP PMT 2003]
Options:
A) 26°C
B) 49°C
C) 35°C
D) 42°C
Show Answer
Answer:
Correct Answer: B
Solution:
According to Newton’s law $ \frac{{\theta _{1}}-{\theta _{2}}}{t}=k[ \frac{{\theta _{1}}+{\theta _{2}}}{2}-{\theta _{0}} ] $ Initially, $ \frac{(80-64)}{5}=K,( \frac{80+64}{2}-{\theta _{0}} ) $
Therefore $ 3.2=K[72-{\theta _{0}}] $ … (i) Finally $ \frac{(64-52)}{10}=K,[ \frac{64+52}{2}-{\theta _{0}} ] $
Therefore $ 1.2=K[58-{\theta _{0}}] $ … (ii) On solving equation (i) and (ii) $ {\theta _{0}}=49{}^\circ C $ .
BETA
