Physics department chair at BC: weather alone could easily deflate ball from 12.5 to 10.5 psi

deroc5050 · Jan 24, 2015

How much does the football WEIGH not PSI when fully inflated. Like 14-15 oz so if you take 16% of the air out of the football does it way like .1 oz less. I know weight is not the issue but I am just curious.

BradyManny · Jan 24, 2015

tmajr3 said:
Can you not read what you just typed? Why in the hell would the Colts balls be filled with 22 degrees colder air? You think the Colts balls were pumped up outside? Omfg

Why not? The Patriots did in the second half. That's one of the few things we know, as the game was held up while they pumped them on the sideline.

kennyb · Jan 24, 2015

tmajr3 said:
Can you not read what you just typed? Why in the hell would the Colts balls be filled with 22 degrees colder air? You think the Colts balls were pumped up outside? Omfg

They don't have to be pumped up outside. What matters is not the air temp at pump up but at pressure reading. Air in a leather bladder is INSULATED. IT TAKE A WHILE FOR IT TO REACH OUTSIDE TEMPERATURE. The Colts balls were probably pumped up in indy for the most part. They were transported by bus in the storage area and thus COLD. THUS when pressure tested the air inside was cold.

Omfg indeed.

The ideal gas law is irrefutable. Get that? If Indys balls didn't go down much then they were colder to begin with. The fact they didn't go down as much is proof of that. The ideal gas law is not debateable. It's like saying gravity is debateable.

kennyb · Jan 24, 2015

I guess you should write the national science board or whatever. The Colts balls didn't lose as much pressure therefore the ideal gas law is wrong. It's been used for hundreds of years but based on that info alone it's wrong.

Omfg.

Dr Pain · Jan 24, 2015

kennyb said:
I guess you should write the national science board or whatever. The Colts balls didn't lose as much pressure therefore the ideal gas law is wrong. It's been used for hundreds of years but based on that info alone it's wrong.

Omfg.

Are you really this dim? Patriots balls are done at the Patriots facility. Colts balls come from Indy in a bus, truck whatever where they would have colder air. Also the NFL has never stated the Colts balls were tested mid game. Show where the NFL said this.

kennyb · Jan 24, 2015

Dr Pain said:
Are you really this dim? Patriots balls are done at the Patriots facility. Colts balls come from Indy in a bus, truck whatever where they would have colder air. Also the NFL has never stated the Colts balls were tested mid game. Show where the NFL said this.

He's assuming the Colts balls didn't go down as much. I've read that too but it's not official.

As for the rest of it you're making my point. I was being sarcastic. The ideal gas law is unassailable. That's why they c all it a law.

His point was it doesn't make sense that ours went down theirs didnt. I said theirs were probably colder. He said I was dumb for thinking the Colts would inflate them outside. I never said or made assumptions as to where the Colts would inflate their bslls. It doesn't matter. It's internal temp at pressure testing that counts as you have pointed out.

juny · Jan 24, 2015

deroc5050 said:
How much does the football WEIGH not PSI when fully inflated. Like 14-15 oz so if you take 16% of the air out of the football does it way like .1 oz less. I know weight is not the issue but I am just curious.

espn sports science said if you deflate by 2psi, the weight loss is like 1.5 grams or the weight of a dollar bill

zydecochris · Jan 24, 2015

juny said:
espn sports science said if you deflate by 2psi, the weight loss is like 1.5 grams or the weight of a dollar bill

That may or may not be true, it depends on how that pressure decrease occurs.

Ideal gas law: PV=nRT. The weight is proportional to the mass of the air which is proportional to the number of moles of the air (n). If the volume V of the football is kept constant (a good approximation), there are two ways to reduce P:

The first way is to let air out of the football. In that case, n decreases, and thus the mass decreases (that must be what they mean by the 1.5 g mass decrease), and the weight would, in fact, decrease.

However, if P decreases because of a temperature drop only, there is no change in "n" and thus there would be NO decrease in the mass and weight of the air.

Of course, the football could "seem" heavier at lower temperatures because it would become less pliant (and thus might travel less on kickoffs). The weight could also actually change in fact if it gets wet (adding the weight of the water).

juny · Jan 24, 2015

zydecochris said:
That may or may not be true, it depends on how that pressure decrease occurs.

Ideal gas law: PV=nRT. The weight is proportional to the mass of the air which is proportional to the number of moles of the air (n). If the volume V of the football is kept constant (a good approximation), there are two ways to reduce P:

The first way is to let air out of the football. In that case, n decreases, and thus the mass decreases (that must be what they mean by the 1.5 g mass decrease), and the weight would, in fact, decrease.

However, if P decreases because of a temperature drop only, there is no change in "n" and thus there would be NO decrease in the mass and weight of the air.

Of course, the football could "seem" heavier at lower temperatures because it would become less pliant (and thus might travel less on kickoffs). The weight could also actually change in fact if it gets wet (adding the weight of the water).

Valid points you bring up.

The video deflated the ball (which is what NE is accused of), no change in temperature. So they weighed the football before/after deflation which came up with 1.5g difference

zydecochris · Jan 24, 2015

juny said:
Valid points you bring up.

The video deflated the ball (which is what NE is accused of), no change in temperature. So they weighed the football before/after deflation which came up with 1.5g difference

Thanks for the clarification, I hadn't seen the actual EPSN video myself. If they let out air then of course the weight would change.

zydecochris · Jan 24, 2015

zydecochris said:
There have been several people on this thread talk about what is or is not possible "according to the laws of physics", but there has been some confusion about what is, in fact, possible. It is true that according to the ideal gas law P1/P2 is proportional to T1/T2, but temperature must be in degrees kelvin and pressure should be absolute pressure, not gauge pressure (12.5 psi is gauge pressure). I happen to be a Physics Professor but rather than write a gigantic E-Mail here, let me refer to the link below which quotes Martin Schmaltz at BU, the article is, IMHO, accurate and succinct. The key issue is whether the balls were inflated indoors (at indoor temperatures) or outdoors (at outdoor temperatures), and where the pressure was subsequently measured. For the balls to have been deflated by 1.6- 2.0 psi in the cold weather (which evidently is only rumored), they would have had to be inflated at about 82 degrees F. So: a 1.6-2.0 psi deflation is, in fact, possible under the right circumstances. I hope the link clarifies things.

http://www.boston.com/sports/footba...ut-the-ball/Eocm5m29nIlh0HRBjFWsYO/story.html

After BB's news conference today, I would like to add an addendum / modification / correction to my post of several days back in another thread. I quoted Martin Schmaltz who said that the balls could decrease by 1.6-2.0 psi if they were filled at 82 degrees F. However, neither one of us considered that if the balls were vigorously rubbed indoors that could (and, in fact would) raise the ball temperature above room temperature (as BB said today) . In addition, Martin's calculations were for a 1.6-2.0 psi drop, while now it seems a smaller pressure drop is being discussed (perhaps 1.5 psi). Thus, it should be possible to have the required deflation in the cold weather even if the balls were filled in a room that not as warm as 82 degrees F, contrary to what I implied in the earlier post. Mea Culpa

VJCPatriot · Jan 24, 2015

Sports Science answered this question - a difference of 2 psi results in a weight difference less than a 1 dollar bill. The weight of the rain that day affected the football's weight and performance more than the internal PSI.

deroc5050 said:
How much does the football WEIGH not PSI when fully inflated. Like 14-15 oz so if you take 16% of the air out of the football does it way like .1 oz less. I know weight is not the issue but I am just curious.

zydecochris · Jan 24, 2015

VJCPatriot said:
Sports Science answered this question - a difference of 2 psi results in a weight difference less than a 1 dollar bill. The weight of the rain that day affected the football's weight and performance more than the internal PSI.

Agreed. I hadn't seen articles indicating that the weight change of the football (due to air being let out) was supposed to be an advantage. The weight of a football is overwhelmingly that of the pigskin, I would think the weight of the air would be negligible (have you ever filled a ballon with air? how heavy is it compared to a football?).

The change in weight of the football due to being waterlogged would be gigantic compared to the slight change in weight due to less air pressure, IMHO.

Sfpat · Jan 24, 2015

The NFL stated that the Colts balls were acceptable when inspected pregame and within limits when measured at halftime and after the game. See the difference. The league has never stated that the pressure was measured pregame. If the Colts balls were say 14.5 psi pregame they would be within limits when measured at halftime and after the game.

tmajr3 · Jan 24, 2015

kennyb said:
They don't have to be pumped up outside. What matters is not the air temp at pump up but at pressure reading. Air in a leather bladder is INSULATED. IT TAKE A WHILE FOR IT TO REACH OUTSIDE TEMPERATURE. The Colts balls were probably pumped up in indy for the most part. They were transported by bus in the storage area and thus COLD. THUS when pressure tested the air inside was cold.

Omfg indeed.

The ideal gas law is irrefutable. Get that? If Indys balls didn't go down much then they were colder to begin with. The fact they didn't go down as much is proof of that. The ideal gas law is not debateable. It's like saying gravity is debateable.

That's a whole lot of speculating on how Indy got their balls inflated . Like I said in my first post, until we know the evidence of the Colts balls, this is all null and void

AzPatsFan · Jan 24, 2015

deroc5050 said:
How much does the football WEIGH not PSI when fully inflated. Like 14-15 oz so if you take 16% of the air out of the football does it way like .1 oz less. I know weight is not the issue but I am just curious.

About 1 gram or the weight of one piece of a torn in half of a dollar bill. It ain't much and likely not discernible to ordinary humans.

Bella*chick · Jan 24, 2015

AzPatsFan said:
About 1 gram or the weight of one piece of a torn in half of a dollar bill. It ain't much and likely not discernible to ordinary humans.

That must mean Mark Brunell is an alien. I knew it all along.

kennyb · Jan 24, 2015

tmjr3 said:
That's a whole lot of speculating on how Indy got their balls inflated . Like I said in my first post, until we know the evidence of the Colts balls, this is all null and void

The ideal gas law is a law of physics. It's not null and void. I don't have to know anything about how indy inflated (it actually doesn't matter at all just the temperature at initial pressure reading anyway).

No matter what indy did the ideal gas law says the pats balls go down 1.5psi if their temp goes from 72 to 45. That's just a cold hard fact of physics. Not a maybe or might Or a theory but fact.

No matter what indy did it doesn't change that. The law has already been proven.

AzPatsFan · Jan 24, 2015

kennyb said:
The ideal gas law is a law of physics. It's not null and void. I don't have to know anything about how indy inflated (it actually doesn't matter at all just the temperature at initial pressure reading anyway).

No matter what indy did the ideal gas law says the pats balls go down 1.5psi if their temp goes from 72 to 45. That's just a cold hard fact of physics. Not a maybe or might Or a theory but fact.

No matter what indy did it doesn't change that. The law has already been proven.

As Mona Lisa Vito would say... "That's not all. The fact that the Colts footballs did not decrease in pressure much, by itself, proves the Colts footballs were cold when first certified."

Physics department chair at BC: weather alone could easily deflate ball from 12.5 to 10.5 psi

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