Work Done by Gas: Pexternal*dV?

AI Thread Summary
When gas in a container expands against a constant external pressure, the work done is calculated as Pexternal*dV. However, the internal pressure of the gas (Pgas) also plays a crucial role in determining the work done. The correct formula for work done by expanding gas is W = ∫ p dV, where p represents the internal pressure over the volume change. The piston experiences forces from both the external pressure and the internal gas pressure. Understanding the contributions of these pressures is essential for accurately calculating the work done by the gas.
suli
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if gas in a container expands against a constant external pressure,
the work done by it is Pexternal*dV.
but the force is generated inside the container, shouldn't we use Pgas to calculate the answer?
 
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You are mistaken (unless you have stated the problem incorrectly). The work done by the expanding gas would be

W = \int p dV over the range from v1 to v2 and p would be the internal pressure.
 
The piston is exerted upon by two pressures, one from the atmosphere or other gas (if any) and the second from the gas inside the chamber. The work done by the gas on the piston comes from the definition of work done by a force. This should solve your problem. Work done by a gas would obviously involve then, the force exerted BY the gas on the piston.
 
Thread 'Variable mass system : water sprayed into a moving container'

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