AIPMT | 2014Heat TransferHard
Question
Certain quantity of water cools from 70oC to 60oC inthe first 5 minutes and to 54oC in the next 5 minutes. The temperature of the surroundings is
Options
A.45o C
B.20o C
C.42o C
D.10o C
Solution
Newtons law of cooling 
First ⇒
= K [65 - θ0]
⇒ 2 = K [65 - θ0] ....(i)
Next ⇒
= K[57 - θ0] ....(ii)
Diving (i) and (ii)
⇒ 285 - 5θ0 = 195 - 3θ0
⇒ 2θ0 = 90
θ0 = 45o
First ⇒
= K [65 - θ0]⇒ 2 = K [65 - θ0] ....(i)
Next ⇒
= K[57 - θ0] ....(ii)Diving (i) and (ii)
⇒ 285 - 5θ0 = 195 - 3θ0
⇒ 2θ0 = 90
θ0 = 45o
Create a free account to view solution
View Solution FreeMore Heat Transfer Questions
The thermal capacities of two bodies are in the ratio of 1:4. If the rates of loss of heat are equal for the two bodies ...Assuming the sun to be a spherical body of radius R at a temperature of T K, evaluate the total radiant power, incident ...A sphere a cube and a thin circular plate all made of same substance and all have same mass. These are heated to 200oC a...Four indentical calorimeters painted in different colours, are heated to same temperature and then allowed to cool in va...One mole of oxygen is contained in a rigid container with walls of inner surface area A, thickness d and thermal conduct...