Thermodynamics Question 11
Question 11 - 29 January - Shift 1
A body cools from $60^{\circ} C$ to $40^{\circ} C$ in 6 minutes. If, temperature of surroundings is $10^{\circ} C$. Then, after the next 6 minutes, its temperature will be ______ ${ }^{\circ} C$.
Show Answer
Answer: (28)
Solution:
Formula: Newton’s law of cooling
By average form of Newton’s law of cooling $$ \begin{aligned} & \frac{20}{6}=k(50-10) \\ & \frac{40-T}{6}=K\left(\frac{40+T}{2}-10\right) \end{aligned} $$
From equation (i) and (ii) $$ \begin{aligned} & \frac{20}{40-T}=\frac{40}{10+T / 2} \\ & 10+\frac{T}{2}=80-2 T \end{aligned} $$
