Exams › NEET › Physics

A body cools from 50.0°C to 48°C in 5s. How long will it take to cool from 40.0°C to 39°C? Assume the temperature of surroundings to be 30.0°C and Newton’s law of cooling to be valid.

1. 2.5 s
2. 10 s
3. 20 s
4. 5 s

Correct answer: 2.5 s

Solution

According to Newton's law of cooling, the rate of cooling is proportional to the temperature difference between the body and its surroundings. The average temperature difference in the first case is 9°C, and in the second case, it is 5°C. The time taken is inversely proportional to the temperature difference, so the second cooling takes (9/5) × 5 = 2.5 s.

Related NEET Physics questions

• An instrument used to measure high temperature is
• Ocean currents are caused by the setting up of in water
• For the same mass, which one of the following has the maximum thermal capacity?
• 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)
• Bunty mixed 440 gm of ice at \( 0^{\circ} \mathrm{C} \) with \( 540 \mathrm{gm} \) of water at \( 80^{\circ} \mathrm{C} \) in a bowl. Then what would remain after sometime in the bowl?
• Mercury boils at \( 356^{\circ} \mathrm{C} \). However mercury thermometers are made such that they can measure temperatures up to \( 500^{\circ} \mathrm{C} \). This is done by :

⚔️ Practice NEET Physics free + battle 1v1 →