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## Main Question or Discussion Point

Hiya! I'm an ameture "maker", and recently I've become interested in air pressure and such. I thought a fun project to help me learn about it would be to make one of those small air cannons that are powered by bicycle pumps (safety first and all that). One thing confuses me though: how exactly does one calculate pressure in psi from volume? I've been thinking about this in terms of air (from a bike pump?) being added to a container of X volume in Y cubic inches per cycle/pump/etc. Is there a set of formulas for how pressure changes this way, or is it supposed to be inferred? Thanks in advance for any help you guys can give me - for the record, I think PF is a lot better than the Stack Exchange :)