Transmission Of Heat Question 197
Question: An object is cooled from 75°C to 65°C in 2 minutes in a room at 30°C. The time taken to cool another object from 55°C to 45°C in the same room in minutes is
[EAMCET (Med.) 1996]
Options:
A) 4
B) 5
C) 6
D) 7
Show Answer
Answer:
Correct Answer: A
Solution:
According to Newton’s law of cooling in first case, $ \frac{75-65}{t}=K[ \frac{75+65}{2}-30 ] $ ?..(i) in second case,$ \frac{55-45}{t}=K[ \frac{55+45}{2}-30 ] $ ?..(ii) Dividing eq. (i) by (ii) we get $ \frac{5t}{10}=\frac{40}{20} $
Therefore $ t=4 $ minutes
BETA
