I'm struggling with a simple calculation, been through the books and can't get an answer I believe.

A cylinder of internal diameter one inch is closed at one end (ie a can with one end open) is plugged with a bung that weighs say 20grams.

If I create an impulse by suddenly releasing compressed air into the cylinder which causes the bung to be released from the cyclinder at 150PSI and assuming the impulse is of a duration of 50mS how do I calculate the change in momentum of the bung?

I know that momentum is mass x velocity and I know that the impulse is Pressure x time, but the dimensions don't match so there is a bit of extra math to do.

TIA

Steve

PS: I wouldn't have asked this question if that chap in Cherokee County hadn't blown up his cannon!