RE: Ideal Gas Law
This has been thrown about in this thread numerous times, and I'm not sure if
this website is correctly calculating things or not, but I decided to try to apply the Ideal Gas Law to this situation.
The Ideal Gas Law equation is pV = nRT, where P=pressure, V=volume, n=number of moles, R=the gas constant, and T=temperature
To use the Ideal Gas Law to determine air pressure, it seems you need to know the temperature, volume of an object & moles of the gas being used.
An NFL football is 4237 cm3
link
Assuming oxygen was used to fill the footballs, according to the calculator on the website I linked, there would be .149252 moles of oxygen in an NFL football, inflated to 12.5 PSI, at 70% degrees.
If you use the same calculator, using 50 degrees (F) as the temperature, .149252 as the moles, and 4237cm3 as the volume of the football, the PSI of the football would be 12.028. If these calculations are correct, then the temperature couldn't have caused the footballs to drop by 2 PSI (although these calculations don't factor in moisture). If the reports of only a drop of 1 PSI are accurate, though, this would explain it.
Can someone with more knowledge of how to use this equation check my work?