- #1

cianfa72

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Hi,

reading the interesting Reversible vs Irreversible Gas Compression and Expansion Work insight by @Chestermiller I would like to ask for clarification on some points.

In the second bullet at the beginning

Applying the Newton's third laws to the massless piston we get

Does it make sense ? Thank you.

reading the interesting Reversible vs Irreversible Gas Compression and Expansion Work insight by @Chestermiller I would like to ask for clarification on some points.

In the second bullet at the beginning

my understanding is as follows: consider an ideal gas contained in a cylinder featuring aSince, by Newton’s third law, the external force per unit area exerted by the surroundings on the gas is equal to the gas thermodynamic pressure at the interface P.

*massless*piston. An external force per unit area ##P_{ext}## is applied to the piston through a bunch of (external) bodies.Applying the Newton's third laws to the massless piston we get

*two*things:- the force per unit area the piston applies to the external bodies through the piston's outer edge is the same (in module) as the external force per unit area ##P_{ext}##
- the force per unit area the thermodynamic pressure of the gas at the piston's inner edge ##P_I## (i.e. the thermodynamic pressure ##P_I## at the piston internal interface) applies to the piston is the same (in module) as the force the piston applies per unit area on the gas inside the cylinder

Does it make sense ? Thank you.

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