Football Physics! [When 12.5 psi Equals 11.9 psi] Its out of season for Steven DeSanto and I, but I wonder how easy it would be for weather to make a NFL Football illegal? Using the Ideal Gas Law, you can make a relationship sowing [(Pressure times Volume) divided by Temperature] is of constant value. You can assume that a volume of a football is nearly constant during any temperature change because the ball will have negligible size difference at two different pressures. Yes, it would expand/shrink a minute amount but not as much as if it were, lets say a partially inflated garbage bag. Here the structure of the leather/rubber, help confine the volume of the ball to a certain size. So you can effectively cancel volume out of the relationship leading to what is referred to as Gay-Lussacs Law. P1/T1 = P2/T2 Important note: temperature must be in Kelvin. 75 Fahrenheit = 297 Kelvin (ball measured at room temp.) 50 Fahrenheit = 283 Kelvin (ball at some point during cold game. 50s at start, 40 at end. I picked 50.) The NFL rule book states pressure must be between 12.5 psi and 13.5, psi. So lets stay legal at the minimal 12.5 psi when measured hours before the game. 12.5/297 = P2 /283 P2 = 11.9 psi 12.5 psi now equals 11.9 psi
Posted on: Thu, 22 Jan 2015 22:41:13 +0000
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