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former9thward

(33,424 posts)
13. The temperature was 50 not 59 at game time.
Fri Jan 23, 2015, 08:13 PM
Jan 2015
Ideal Gas Law:

pV=nRT
where p is pressure, v is volume, n is the number of moles of a gas, R is the Universal Gas constant, and T is temperature.

Remember, what we do to one side of the equation, we have to do to the other side as well. For example, if we increase the pressure (p), then the temperature (T) would have to increase as well. That also means that a change in volume (V) would mean a change in temperature.

We make the following assumptions, based on what we know about the procedure regarding regulation footballs in the NFL and about the Ideal Gas Law:

1) V, the volume of gas (air) in the ball should not change, since (according to procedure), no air is added to or subtracted from the ball after reaching the proper inflation,

2) n will not change for the same reason as above,

3) R does not change, since it is a universal constant.

Now, let's just change the way the equation looks by moving all the letters to one side of the equation:

pV/nRT = 1
From here, we need to think of this as two different times: the pressure, temperature, etc. from when the balls were checked and the pressure, temperature, etc. out on the field. Let's set those to be equal:

p1 V1 / n1 RT1 = p2 V2 / n2 RT2,
where the 1 represents the initial readings and 2 represents the readings on the field. Since the volume will not change (assuming no air is added or taken away from the ball), then V1 = V2, and those can be cancelled. For the same reason, n1 andn 2 can cancel. The R 's cancel, since R

is a constant. We are left with a simple equation:

p1 / T1 = p2 / T2
Now, we can start solving this puzzle quite easily! But before we do, we also have to know the atmospheric pressure during the game, since p in this case is the absolute pressure; the pressure inside the ball plus the pressure of the atmosphere (which exerts a force on the ball as well).

At 6pm, the atmospheric pressure at nearby Norwood Airport was 1009.5 mb (1009.5 hPa or 100950 Pa).

Let's assume that each ball was inflated to the minimum pressure required to meet the NFL rules regarding proper inflation: 12.5 psi. We convert psi (English) to pascals (Metric), which comes out to 86,184.5 Pa and assume a room temperature of 68ºF (20ºC) which converts to 293.15 K (Kelvin, the Metric equivalent). We now have,

(86,184.5 Pa + 100950.0 Pa) / 293.15 K = (p2 + 100950.0 Pa) / T2.
We're down to two variables. But we also know the temperature on the field at the start of the game was reported as 51ºF/10.6ºC (283.15 K). Plug it in...

(86,184.5 Pa + 100950.0 Pa) / 293.15 K = (p2 + 100950.0 Pa) / 283.15 K
Neat! Look, we're left with a solvable equation with one variable, p2, which is the pressure of the air inside the ball at game time! Let's solve this riddle...

Isolate the lone variable:

{ * 283.15 K} - 100950.0 Pa = p2
79,800.9 Pa = p2 ---> 11.8 psi
83,244.6 Pa is 11.8 psi, so, according to these calculations, the balls could have been under-inflated by 0.7 psi on the field, just due to the change in temperature from inside to outside. This makes sense given the very first equation, which shows that a decrease in temperature would force a decrease in pressure, assuming the same volume of air in the football.

If we use an indoor temperature of 80º, we would get a final pressure of 11.0 (10.99) psi.


http://www.wcsh6.com/story/weather/2015/01/20/inflate-gate-weather-roll/22065861/

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0 members have recommended this reply (displayed in chronological order):

All I can think of is louis-t Jan 2015 #1
NFL has ruled out the temperature as a factor. eom MohRokTah Jan 2015 #2
They don't believe in physics? trof Jan 2015 #3
They claim that temperature variations... Bad Thoughts Jan 2015 #4
Aha! Now we're parsing. trof Jan 2015 #6
I believe it would have required a 45 degree drop in temperature Bad Thoughts Jan 2015 #8
The temperature was 59 degrees MohRokTah Jan 2015 #5
Yes, but it was raining. Pouring down. trof Jan 2015 #9
It is physically impossible for the balls t deflate by 2 PSI... MohRokTah Jan 2015 #10
The temperature was 50 not 59 at game time. former9thward Jan 2015 #13
Exactly. Barometric pressure changes have an effect too! trof Jan 2015 #15
Using your methodology, I calculated that dumbcat Jan 2015 #18
I agree. former9thward Jan 2015 #19
Joule-Thompson Effect - look it up. jberryhill Jan 2015 #36
Do you actually own a compressor? dumbcat Jan 2015 #43
I guess we need to know what they fill the balls with jberryhill Jan 2015 #44
They fill them with helium so they'll stay in the air longer. randome Jan 2015 #45
Exactly. And that is the crux of the problem dumbcat Jan 2015 #47
There was one article... jberryhill Jan 2015 #48
Of course, one of these would work much quicker: icymist Jan 2015 #20
No question. former9thward Jan 2015 #22
All those fancy calculations do NOT account for the fact that the Colts balls were subject pnwmom Jan 2015 #28
The calculations aren't all that fancy jberryhill Jan 2015 #39
Failure of invalid equilibrium assumptions jberryhill Jan 2015 #38
it's not so much the ambient conditions that are relevant... mike_c Jan 2015 #24
They think the rules of physics apply equally to Colts and Patriots balls. pnwmom Jan 2015 #27
Except the footballs on the other side of the field were and remained properly inflated mythology Jan 2015 #31
Accuweather says based on the temp change the FB's would have deflated by .4 psi not 2 psi Quixote1818 Jan 2015 #7
But the evaporation factor! trof Jan 2015 #11
It was raining, so almost no evaporation was occuring in the moist air Quixote1818 Jan 2015 #50
so balls on one side of field deflate, and those on the other side do not? magic not science on point Jan 2015 #12
Both sides supply the balls they will play with on offence. former9thward Jan 2015 #14
'human intervention'. Ya think? trof Jan 2015 #16
That or God. former9thward Jan 2015 #17
I'm going with God. trof Jan 2015 #21
If there was a simple scientific situation based on storage or testing conditions, pnwmom Jan 2015 #30
Temp was 51 at kickoff. Cali_Democrat Jan 2015 #23
Seems a reasonable possibilty: Faryn Balyncd Jan 2015 #25
How would that explain the 12th Patriots ball or all 12 Colts balls? pnwmom Jan 2015 #26
It might depend on the internal temperature of the balls before inpection. The temperature drop from Faryn Balyncd Jan 2015 #32
I read that all 11 balls were at least 2 under, not just one of the balls. pnwmom Jan 2015 #33
There have been conflicting reports: Faryn Balyncd Jan 2015 #34
If the human intervention took place in the beginning, pnwmom Jan 2015 #35
That's interesting. Faryn Balyncd Jan 2015 #37
when its cold and I go outside olddots Jan 2015 #29
NO! No! No! KMOD Jan 2015 #40
Perhaps the tapering could have been by using heat Faryn Balyncd Jan 2015 #42
I think DeflateGate is overblown davidpdx Jan 2015 #41
"Look, you don't understand. There was shrinkage." WinkyDink Jan 2015 #46
I was in the pool! I was in the pool! pintobean Jan 2015 #49
;-) WinkyDink Jan 2015 #51
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