General Pressure Question, pressure inside of a closed cylinder

Question

johnweldon1993 · Answer

Terrible question, though I'm kind of messing up here...perhaps I'm tired

regardless, for a cylinder of $\large R = 4 in.$ and $\large h = 7 in.$ COMPLETELY full of air, no other fluids what is the pressure inside of the cylinder?

I've used the ideal gas law $\large PV = mRT$
Solving for P: $\large P = \frac{mRT}{V}$ and since we dont know the mass of air, I simply replaced $\large m = \rho V$ resulting in $\large P = \rho RT$

This is where I'm confused...since the air in enclosed in a cylinder...SHOULDN'T the volume of the cylinder play a role here?

irishboy123 · Answer

have a look here https://i.gyazo.com/1e47b2df0b7e260ff78c5da175b6422d.png it's all about what you take m to mean in your expression of the ideal gas law

johnweldon1993 · Answer

Yeah no, I had a terrible blonde moment here haha, it took actually calculating it out to realize it was just atmospheric pressure >.< Thanks @IrishBoy123 !