Over Thanksgiving break, my family and I watched the New England Patriots defeat "our" team, the New York Jets. As we watched, Tom Brady and the "deflategate" scandal were discussed. During lecture this past week, as we were learning about the ideal gas law, I began to think about Tom Brady's scandal in a physics frame. I did a little research and found that air pressure in a regulation NFL football is about 12.5-13.5 psi. I wanted to see how that pressure could change in the face of changing temperatures, as NFL football seasons span from pre-season in August to the Super Bowl in February. If an NFL regulation-sized football was used in a game in August, how would the pressure of the gas within the ball change if it were February? I used Guy-Lussac's Law to determine this, as the volume of the football would not change.
I researched the average temperatures in Foxborough, MA, where the Patriots have their stadium. I found that the average temperature is 67 degrees F in August and 14 degrees F in February. If a football were pumped with air in August so that the pressure inside the ball was 13 psi, what would the pressure of a same-sized ball be in February weather conditions?
T(1)= 67 degrees F
T(2)= 14 degrees F
P (1)= 13 psi
P (2)= ?
Guy Lussac's Law: P(1)/T(1) = P(2)/T(2)
13psi / 67 deg. F = P(2) / 14 deg. F
P(2) = 2.72 psi
The pressure of the ball in February weather conditions would 2.72 psi, which is significantly smaller than 13 psi in August weather conditions.
Did Tom Brady actually deflate the balls? or did the NFL not account for the impact of temperature changes on pressure?