Work done by gas

1. Aug 17, 2005

suli

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?

2. Aug 17, 2005

FredGarvin

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.

3. Aug 17, 2005

maverick280857

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.