Question

A body cools from a temperature of $60^\circ\mathrm{C}$ to $50^\circ\mathrm{C}$ in 10 minutes and $50^\circ\mathrm{C}$ to $40^\circ\mathrm{C}$ in 15 minutes. The time taken in minutes for the body to cool from $40^\circ\mathrm{C}$ to $30^\circ\mathrm{C}$ is

• A. 30
• B. 20
• C. 25
• D. 40

Hint:

When using Newton's Law of Cooling $\frac{dT}{dt} = -K(T_{avg} - T_s)$, always find the surrounding temperature $T_s$ first using the first two conditions.

Answer 1

The Correct Option is A