Physics · Heat transfer: conduction, convection and radiation
The excess temperature of a body falls from to in 5 minutes, then the time to fa
The excess temperature of a body falls from \( 12^{\circ} \mathrm{C} \) to \( 6^{\circ} \mathrm{C} \) in 5 minutes, then the time to fall the excess temperature from \( 6^{\circ} \mathrm{C} \) to \( 3^{\circ} \mathrm{C} \) is (assume the Newton's cooling is valid)
- A. 10 minutes
- B. 7.5 minutes
- C. 5 minutes
- D. 2.5 minutes
Step-by-step solution
According to Newton's law of cooling, the rate of cooling is proportional to the excess temperature. This leads to exponential decay, so the time to halve the excess temperature is constant. From 12°C to 6°C (half) takes 5 minutes, thus from 6°C to 3°C (another half) also takes 5 minutes.
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