An empty pressure cooker of volume 10 litres contains air at atmospheric pressure $1 0^{5} Pa$ and temperature of $2 7^{\circ} C$ . It contains a whistle which has area of $0.1 cm^{2}$ and weight of 100 g . What should be the temperature (in °C) of air inside so that the whistle is just lifted up?

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TestHub · Accepted Answer

Whistle just lifts: P in ​ A = P o u t ​ A + m g , so P in ​ = 1 0 5 + 1 0 − 5 0.1 × 10 ​ = 2 × 1 0 5 P a . Constant volume: T 1 ​ P 1 ​ ​ = T 2 ​ P 2 ​ ​ ⇒ T 2 ​ = 300 × 2 = 600 K = 32 7 ∘ C .

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