[Leaning Right]

TexasGator very alertly pointed out an error in my post #60’s calculation of the football's pressure: When using an Ideal Gas Law, the pressures must be absolute, and not pressures read from a guage.

My improved calculation: A football with a gauge pressure of 12.5 psi at 72 F should have a gauge pressure of 11.4 psi at 49 F.

This calculation assumes that the air is behaving as an ideal gas, and the ball is at sea level. Neither is true of course, but won't affect the results very much. What might affect the results more are other factors, like the non-rigid behavior of the ball, as lepton has pointed out.

[TexasGator]

pv = nRT

Assuming v, n, R are constant:

P/Po = T/To

p= T/To/Po

P = (49+273) / (72+273)*(14.7+12.5)= 25.4 psia

PSIG = (25.4-14.7) = 10.7