Physics - Heat & Thermo Question with Solution | TestHub

PhysicsHeat & ThermoRadiationMedium2 minQB

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Passage / Comprehension

Newton's law of cooling says the cooling rate is directly proportional to the temperature difference between a body and its surroundings. The proportionality constant does not depend on the body's temperature.

A body is kept in room temperature of the room is 30°C. Initial temperature of the body is 40°C & becomes 36°C in 2 minutes, then find the time taken by the body to decrease the temperature further by 4°C.

Options:

Answer:

Solution:

From Newton's law of cooling,

$\frac{d θ}{dt} = k (θ - θ_{S}) \Rightarrow \frac{4}{2} = k (38 - 30) \Rightarrow k = \frac{1}{4}$

Again,

$\frac{d θ}{dt} = k (θ - θ_{S}) \Rightarrow \frac{4}{t} = \frac{1}{4} (34 - 30) \Rightarrow t = 4 min .$

Stream:JEESubject:PhysicsTopic:Heat & ThermoSubtopic:Radiation

⏱ 2mℹ️ Source: QB

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