neali
On the Game Day Roster
- Joined
- Oct 12, 2011
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How do you fine the Pats for the laws of physics.
Using the ideal gas law, a ball that was filled in a 75 F room to 12.5 psi would be at 10.97 psi at 45F.
Most people doing the calculation don't realize that the ideal gas law obeys absolute pressure, not pressure above atmospheric. You have to add atmospheric pressure (14.7) psi to get absolute pressure.
P1gauge = Pressure when ball is inflated equals 12.5 psi.
P1absolute = P1guage + 14.7psi which is pressure at sea level and is close enough.
P2absolute and P2guage are to be solved for.
T1 = 75F = 23.88C = 297.04K
T2 = 45F = 7.22C - 280.37K
Assume Pats inflated the balls to 12.5 psi
P1g =12.5 psig
p1a = 12.5 +14.7 = 27.2 psi absolute
ideal gas law says PV=mRT. R is a Constant and assume the mass of air in the ball stayed the same and the volume of the ball was relatively a constant although it might change a miniscule amount.
So P2a/P1a = T2Kelvin/T1Kelvin solve for P2a = T2/T1 * P1
T2/T1 = 280.37/297.04 = 0.9439
P2a = 27.2 * 0.0439 = 25.67
P2g = P2a - 14.7 = 10.97 psi gauge!!!!! Almost exactly what was measured
Why did the 12th ball not measure underinflated? Because Blount threw it into the stands.
Why did the Indy balls measure ok? Some possible reasons.
1. Those balls were transported in the cargo hold of a plane and probably stored in an equipment truck prior to the game and never warmed to room temperature?
2. The Colts inflated theirs to 13.5 outside and they never experienced los of pressure from cooling. This was either done unintentionally or intentionally because Irsay was setting up the Pats.
Using the ideal gas law, a ball that was filled in a 75 F room to 12.5 psi would be at 10.97 psi at 45F.
Most people doing the calculation don't realize that the ideal gas law obeys absolute pressure, not pressure above atmospheric. You have to add atmospheric pressure (14.7) psi to get absolute pressure.
P1gauge = Pressure when ball is inflated equals 12.5 psi.
P1absolute = P1guage + 14.7psi which is pressure at sea level and is close enough.
P2absolute and P2guage are to be solved for.
T1 = 75F = 23.88C = 297.04K
T2 = 45F = 7.22C - 280.37K
Assume Pats inflated the balls to 12.5 psi
P1g =12.5 psig
p1a = 12.5 +14.7 = 27.2 psi absolute
ideal gas law says PV=mRT. R is a Constant and assume the mass of air in the ball stayed the same and the volume of the ball was relatively a constant although it might change a miniscule amount.
So P2a/P1a = T2Kelvin/T1Kelvin solve for P2a = T2/T1 * P1
T2/T1 = 280.37/297.04 = 0.9439
P2a = 27.2 * 0.0439 = 25.67
P2g = P2a - 14.7 = 10.97 psi gauge!!!!! Almost exactly what was measured
Why did the 12th ball not measure underinflated? Because Blount threw it into the stands.
Why did the Indy balls measure ok? Some possible reasons.
1. Those balls were transported in the cargo hold of a plane and probably stored in an equipment truck prior to the game and never warmed to room temperature?
2. The Colts inflated theirs to 13.5 outside and they never experienced los of pressure from cooling. This was either done unintentionally or intentionally because Irsay was setting up the Pats.