Q 11-10-036NEETJEE MainEAMCET 2012 (Medical)Medium
Equal masses of three liquids A, B and C have temperatures $10°$C, $25°$C and $40°$C respectively. If A and B are mixed, the mixture has a temperature of $15°$C. If B and C are mixed, the mixture has a temperature of $30°$C. If A and C are mixed, the temperature of the mixture is
Answer: (A) $16°$C
Equal masses, so only specific heats matter.
A and B: $s_A(15 - 10) = s_B(25 - 15) \Rightarrow s_A = 2s_B$.
B and C: $s_B(30 - 25) = s_C(40 - 30) \Rightarrow s_B = 2s_C$. So $s_A = 4s_C$.
A and C: $4s_C(\theta - 10) = s_C(40 - \theta) \Rightarrow 5\theta = 80 \Rightarrow \theta = 16°$C.
Solution by Sreeraj P, M.Sc Physics