The Physics of Natural Football Deflation

I've noticed that American so-called "foot" "balls" have some sort of inflation problem. They seem to end up in some sort of ovoid shape, rather than the correct spherical shape. This also seems to prevent them from having adequate contact with the players' feet. The objects are therefore neither foot-related, nor balls.

I hadn't realised it was a physics problem. Interesting.

 

Dr. Sage did you assume P1 = 14.7 + 12 = 27 psia

 

there's a lot of deflated balls around here this week.

 

Well if any of the officials drove a Prius, they would have pulled out their pressure gauge and made sure their balls are fully inflated. Reminds me of:

Bob Wilson

 

Yes it's just like tire pressure calcs.
Constant volume assumption probably good (works for tires).

I am not following the news story too closely but possibly the compressor heats up the air a little so I guess that's plausible.
Of course I assume football managers they know all that from experience, so no excuses please.

 

^^ Did anyone perform some due diligence by checking the game balls provided by the other team? The temperature shift should change both equally.

 

Ahhh, the football incubator with constant pressure and temperature regulator.

Both teams played with the same d*mn ball. If it helped one quarter back and receivers, it helped the other. Someone is smoking something to claim just one team benefited.

Perhaps just coat the ball with lard and be done with it. The fumbles would make the game more interesting . . . and boxi^i^x^o^b hockly-like. (i.e., rugby for those who drive on the wrong side of the road)

Bob Wilson

 

I'm seeing multiple statements that the balls are changed very frequently. Each team supplies the balls for its own offensive plays, and different balls are used for kicking. So, no, they are not using the same single ball in the same way.

 

a lot of chatter around here, but no answers so far. i'm waiting for someone to ask the refs, since they handle the ball between every play, why didn't they notice anything, yet the indy receiver who intercepted it did?

 

The balls are neither a fully rigid enclosure (where only the pressure varies with temperature) nor a fully elastic enclosure (where essentially only volume varies with temperature). There is some amount of elasticity, so more air needs to be let out than what is noted to reduce the pressure than what the calculation show. I do not know what this factor is.

 

• One team could being compressing (heating up) ambient air for injection into the ball just before handing the balls over for inspection, while the other could be using highly compressed air already cooled to ambient (or even a liquid CO2 cartridge), so it cools upon injection.

 

this is why the umps just keep chucking out new balls in baseball. if the pitcher even looks sideways at the ball, ump chucks out a new one.

 

I am recommending they fill with N2.
Just kidding...

 

...sounds like the balls are approved (weighed?) by the Ref before the game. So to show up "light" low weight a few hours later the implication would have to be someone is tampering with the balls after approval. The Colts are saying what they noticed is the balls they intercept are light-weight.

Unless something really sinister going on (see below), once the Ref approves it, the NFL cannot say well we approved it, but we did not check well enough.

Or how about filling with O2 which diffuses 4x faster than N2? Or any molecule (Argon?) smaller than N2 on a molecular scale...no way these guys are not that smart?? Any chemistry majors on the team? Or finding a way to make a slow leak? or selecting balls ahead of time they know have a very slow leak rate? Mositure/water I guess could be played with.

Anyone know how much pressure a fully inflated football would lose over 24-hrs?

Check this out...sounds like they really manipulate the balls heavily before use...
Qbs Get On The Ball, Reach Goal - Sun Sentinel

 

funny story in usa today, if you believe the science.