06 February 2015

The Physics of Tom Brady's Balls - Again

One of the cool things about the tools we create is that we can easily adapt them to cover scenarios other than those for which they were originally created. In this case, we've adapted our original tool for considering the physics of how Tom Brady's balls might have become deflated in cold temperatures to account for atmospheric air pressure. Sal Khan of the Khan Academy explains why that matters.

It turns out that we can directly add that atmospheric air pressure to the measured air pressures in our original tool, although we're sticking with the indoor temperature of 68 degrees Fahrenheit as the temperature of the room in which Tom Brady's balls were inflated given the cost of heating the interior rooms of the stadium above the level recommended by the U.S. Department of Energy during the winter. Especially since it is owned by the Indiana Stadium and Convention Building Authority, part of the state government of Indiana, which really shouldn't be looking to spend lots of taxpayer cash on overheating visiting NFL teams.

Having set the values that govern the physics, let's see how much the change in temperature accounts for the deflation of Tom Brady's balls....

Football Inflation Data Before the Game
Input Data Values
Initial Measured Internal Pressure [psi]
Initial Volume [cubic inches]
Initial Temperature [degrees Fahrenheit]
Football Inflation Data at Halftime
Internal Pressure at Halftime [psi]
Volume at Halftime [cubic inches]
Temperature at Halftime [degrees Fahrenheit]

How Much of Football Deflation Is Explained by Weather?
Calculated Results Values
Expected Internal Pressure of Footballs at Halftime
Actual Internal Pressure of Footballs at Halftime
Percentage of Change in Pressure Explained by Change in Temperature
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The updated math says that even with the updated pressure data, the change in temperature is only enough to account for 46% of the balls deflation, which means that other factors have to be at work to explain the full amount of the measured deflation. Using Sal Khan's 75 degree figure, the percentage explained only rises to 64%, meaning that there is still more than a third of the deflation that needs to be explained should that higher temperature prove accurate.

The question now is whether the NFL has the integrity to dig deeper to get the rest of the explanation. Our guess is that now that the Patriots are the Superbowl champions, they have very little interest in really getting the full story.