Transmission Of Heat Question 181

Question: The temperature of a liquid drops from $ 365K $ to 361 K in 2 minutes. Find the time during which temperature of the liquid drops from $ 344\ K $ to $ 342K $ . Temperature of room is $ 293\ K $

[RPET 1997]

Options:

A) 84 sec

B) 72 sec

C) 66 sec

D) 60 sec

Show Answer

Answer:

Correct Answer: A

Solution:

$ \frac{365-361}{2} $

$ =K[ \frac{365+361}{2}-293 ] $ = 70 K

Therefore $ K=\frac{1}{35} $ Again $ \frac{344-342}{t}=\frac{1}{35}[ \frac{344-342}{2}-293 ]=\frac{10}{7} $

Therefore $ t=\frac{14}{10} $ min = $ \frac{14}{10}\times 60=84 $ sec.