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Mechanical Properties Of Fluids

Question
CBSEENPH11018102

An ideal gas of bulk modulus K is enclosed in a container of fixed walls. Find the stress set up in the gas when heated through temperature θ. Let γ be the temperature coefficient of cubical expansion of gas. 

Solution

Given, an ideal gas of bulk modulus 'K' and is heated to a temperature θ

Increase of temperature of gas at constant volume is equivalent if the gas is first heated at constant pressure and then compressed isothermally to original volume.

Let V be the volume of gas. When it is heated through a temperature θ at constant pressure, then the increase in volume of gas is,

∆V = Vγθ

Now compress the gas isothermally so that the volume decreases by ∆V = Vγθ.

If ∆P be the stress set up in the gas, then

K=stressstrain=ΔPΔV/V=ΔPγθ         ΔP = Kγθ