Posted on 01/28/2015 1:26:13 PM PST by Brad from Tennessee
Just fill the ball with warm humid indoor air, then when it temperature-equalizes with the 25°F cooler outdoor air on your AFC Championship playing field some of the water vapor in the ball will condense into water, leaving less air in the ball, solving the great mystery: how did the footballs used by the Championship winning New England Patriots show 12.5 psi of inflation pressure in the official pre-game check but only 10.5 psi when checked at halftime?
There is also a decrease in pressure due to the cooling of the molecules that remain gaseous. Those air molecules are not zipping around as fast as they were so they exert less outward pressure on the ball. But according to the ideal gas law, if there were no reduction in the number of gas molecules in the balls it would have taken a large drop in temperature, about 40°F, to cause the observed drop in air pressure. So says Boston College professor Martin Schmaltz:
"In order for a ball to register a 10.5 PSI in a 50 degree environment [the temperature on the field at halftime] but register a 12.5 PSI in the testing environment, the ball would have to have been inflated, stored, and/or tested in a 91 degree environment."
(Excerpt) Read more at wattsupwiththat.com ...
Mystery solved?
Inflate them with nitrogen like they do race tires.
Someone said the cold-temperature issue had already been checked.
If the balls had been inflated at 20°C and then used at 5°C, the difference in pressure would have been less than 15/273 (also known as 5.5%). That’s not accounting for moisture condensation, which I doubt would make much of a difference.
God, you’re a genius... only why only the Patriot balls were deflated...”Old shoe cleats breath?”
I believe the balls used by the Colts act as controls. 12 out of 12 of the Colts balls were within the specified PSI. For the Patriots 11 of 12 were out of the specified PSI.
The exact pressure in the footballs has not been confirmed by the NFL. Balls inflated to minimum pressure at 70 degrees will certainly be below pressure at 50 degrees. And that’s IF (big IF!) gauges are actually accurate.
Dry Nitrogen. I suggested that last week!...................
I believe the official marked them without ever testing them before the game. It actually seems to be the most logical solution.
Nitrogen loses pressure when cooled just like every other gas. The difference would be the lack of water vapor condensing inside the ball and chemical reaction between the oxygen and the rubber bladder, both of which should be a small fraction of the pressure drop.
Doesn’t the pump heat up as you inflate the balls to begin with? So you could be dumping warmer than room temperature air into the balls before sending them out in the cold.
I don’t care one way or the other. I don’t watch football anyway.
I’m just suggesting a means of eliminating the problem of pressure rising and falling with temperature. Pressure control is why race tires are inflated with nitrogen.
I saw a “How do they do that?” type of show on Discovery or one of the cable channels just a couple of weeks prior to this imbroglio. The episode was on the manufacture of NFL footballs at the factory in Ohio(?).
The last thing they do before putting the balls in the carton to be shipped to the games is inflate them, inside a holder, with air from the factory supply conduits. Factory air supplies have driers, filters and in some instances coolers to remove dirt, oil and MOISTURE from the supply lines before getting to the end user. CNC machines and precision measuring machines that use air for motors are especially sensitive to oily and moist air, so I doubt there was much moisture in the balls...............
Air is 70% nitrogen.
Is it possible that the Colts’ balls were inflated at the maximum to begin with, while the Patriots’ were at the lower end of the legal amount? That would account for one team’s still being legal. Just throwing it out there.
Dry nitrogen and the NFL providing the balls would kill the issue dead.
This is probably all an evil plot by the Nerf marketing people, trying to get the League to switch to airless footballs. ;-)
The absolute pressure would drop by that much. The gauge pressure (absolute minus 14.7 psi atmospheric) would drop by more.
(12.5 + 14.7) * (278.15/293.15) = 25.8. Subtract atmospheric pressure of 14.7 and get 11.1 psi or an 11% drop in gauge pressure.
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