# Calculating the escape velocity of a pressurised gas

## Main Question or Discussion Point

Well this question I've had since highschool (first year mech), how would i calculate escape velocity of a gas if i know volume, diameter of the hole, pressure, temprature and mass.

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Simon Bridge
Homework Helper
Same as the escape velocity of anything... gas molecules are no different.

no i meant from a container like a gas canister or something something like this : http://www.sz-wholesaler.com/userimg/1068/1074sw1/co2-cylinder-for-lifejacket-799.jpg [Broken]

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mfb
Mentor
If the diameter of the hole is small compared to the container (=> the gas in the container does not move in a significant way), you can look at a small volume of gas and use energy conservation: The pressure difference inside<->outside gives an energy density*, this energy gets released to accelerate the gas.

*to be more precise, I think you should use adiabatic expansion and calculate the released energy

Simon Bridge