/sci/ - Science & Math

>>7029087
>pounds per square inch
>Fahrenheit

Get your shit together, Murica.

>>7029087
what gas? I am assuming uranium hexafluoride because you failed to specify constraints.

>>7029091
the fbi would like to have a talk

>>7029091
RETARD ALERT!

12.5 psi - 2 psi = 10.5 psi

There's some math for you. No need to thank me.

>>7029087
Using the simple ideal gas equation PV=nRT and assuming constant volume,
Hot:
12.5psi*V=nR 295K
Cold:
10.5psi*V=nR 283K

If everything is true then 283/10.5=295/12.5, if you do the math you get 12 psi as the final result from that temperature difference. So if that is from the temperature change then the volume would have to be increased by 14% for it to be true (almost identical math for if you were to let out gas from the ball, except opposite, 14% more air in the hot ball).
If you want the volume to be constant with loss of pressure due solely from temperature change, then 10.5/12.5=T/295 and your temperature is 248K=-13 F

Strictly speaking the volume is needed to know if air was let out.

>>7029087
this is pol or sports arguing about the superbowl
>rednecks

http://en.wikipedia.org/wiki/Ideal_gas_law
http://en.wikipedia.org/wiki/Pressure_measurement#Absolute.2C_gauge_and_differential_pressures_-_zero_reference
Educate yourself.

That goes for most of the people in this thread, actually. Read the second link.

>>7029142

Yep. Too many variables unaccounted for, because it is pretty ludicrous to assume that Foxborough got down to -25 C by halftime.

>>7029762
It really isn't, the ideal gas law under is plenty accurate for these purposes if you use it properly (under the assumption of isochoric cooling) and understand that the given pressures are gauge pressures, rather than absolute pressures (unlike this guy >>7029142 assumed). The only thing missing for this method is atmospheric pressure, but if you assume one standard atmosphere then it actually comes out to right around 10.5 psig.

>>7029770

I assumed that the psi readings were gauge pressures.

Also, don't we need a couple more variables to use IGL?

>>7029778
>Also, don't we need a couple more variables to use IGL?
Not if you assume n1=n2 and V1=V2.

>>7030500

Even if we don't, you end up with a situation using IGL where Avogadro's law sets them equal to each other, which cancels them out, leaving you with just Gay-Lussac's law.

Which, just dealing with pressure and temperature, says that to go from RT (298 K) and 12.5 PSI to 10.5 PSI requires a temperature drop to ~250 K, or -23 C, and it never got that cold in Foxborough. Coldest recorded temperature I could find of the surrounding air was about 278 K, which would only drop about 0.8 PSI or so.

Unless my math is completely off.

However, if there are other shenanigans involved, it is still probable.

>>7029087
Tom Brady in Super Bowl = more $ for the NFL than if they suspended him.

Integrity of pro athletics = 0.

I ran some numbers. for a 12.5 PSI football to go to 10.5 PSI at 45 F, it would have needed to start out at 140 F.
Belichick is lying through his teeth.

>>7030608
My math says going from 72F to 51F results in pressure drop to 11.9 psi

am i wrong

>>7030987
Need to add atmospheric pressure (14.7 psi) to both of your pressures, I forgot about it in >>7029142 Overall answer I get is ~32F for temp that the pressure drop occurs at.

>>7029087
/sci/ can't identify a question about the ideal gas law as a homework problem...

>>7030998

That's only if we want absolute pressure. We're not interested in that here.

>>7030987

That's fairly close to my numbers. It was taking roughly 23.8 C change to move 1 PSI in either direction.

I'm getting that the pressure at 51°F would be 82.78KPa, meaning 12psi.

I did this in SI units, sorry if it confuses fans of the Imperial system.

Assuming constant V and constant n,
(86.184KPa) (V)= nR (295.372 K)
and
Vx= nR (283.7056)
So we et P1/T1 = P2/T2.

For the pressure to be 72.395KPa (10.5psi) the temperature would need to be 248.114K (-13.1°F)

>>7031000
It's not a homework problem, dingus. An American football team was recently accused for cheating by deflating footballs.

>>7031979
An American American football team or an American association football team?

>>7031976
>>7030987
>>7030969
>>7030608
>>7029142
>ITT: People don't understand the difference between absolute pressure and gauge pressure, nor the relevance of them to the gas laws
>>7031788
>That's only if we want absolute pressure. We're not interested in that here.
Yes, we are. Just like how the gas laws depend on absolute temperature, they depend on absolute pressure as well. If you ignore atmospheric pressure, you'll fuck up your result by a fairly large percentage.
>P1 = 12.5 psig + 14.7 psia = 27.2 psia
>T1 = 298 K, T2 = 278 K
>P1/T1 = P2/T2
>Blah blah algebra and attention to units
>P2 = 25.37 psia = 10.67 psig

>>7032726
Your temperatures are wrong. It was 75 degrees Fahrenheit (297 K) when the balls were inflated and 51 degrees Fahrenheit (284 K) outside.

>>7032693
>A football team or a bunch of DYEL mexican faggots no one cares about?

can someone give me a TLDR; for me tocopy pasta back to /sp/
the whole board is wondering a couple things
1, could the climate do it
2 temperature in room and on field at half (not at start's 51 because the temp went down with the sun)
3 are bill nye and NDTyson qualified for this?

>>7032862
Why does it even matter?
The other team's balls were inflated properly, admittedly I don't know much about the details of any sportsball but I assume each team provides balls and it's not just all from one team.
There have been many many games played in cold weather and lots of those started with the sun up and played after it went down. None of those teams seemed to have problems with keeping their balls at the correct pressure.

>>7032760
I just used the temperatures that >>7031976 used. I can't be assed to verify this shit, all I care about is that people are properly grasping the depth of this rather simple problem.

>>7032895

yes both teams provide their own balls(except for kicking plays). the colt's qb is on record for liking high inflated balls(13.5 psi) to get more range out of them and would intern make conditions to preserve a high psi

also a few ESPN sources say 1 ball was 2psi down and 10 were around 1-1.3

also refs never check balls after initial filling(which the reffs do) unless a complaint is made so other games are moot
>that feel when moot is kill

To my knowledge, this is all assuming the ballls were measured outside as well-- And though I'm hardly educated on the subject, there should be no effect if the balls themselves were a different temperature.

Does anybody have a link to the lab study the NE fans keep citing? I want to laugh at their process again.

If the footballs were wet would that affect the pressure?
What about 'rubbing' the footballs 'vigorously'?
Also what if they used an air compressor to inflate.. would the air be heated?

>>7032966
https://www.youtube.com/watch?v=CxsXFX3tDpg

http://www.headsmartlabs.com/#in-the-news
>has data on whiteboard
>hasn't shared whiteboard
>no metrics

>>7032981
>If the footballs were wet would that affect the pressure?
Slightly if wet on the outside, significantly if humid on the inside.

>>7032981
if the compression of the air heated it up the air and nozzle would cool down during decompression

>>7032994
>tested surface wetness and temperature
>at the same time

>>7030969
Got the same answer - does it matter if it's PSIA or PSIG? I used PSIG.

>>7033070
>does it matter if it's PSIA or PSIG?
Yes. You have to use absolute pressure, just like you have to use absolute temperature.

>>7033070
If you're dealing with differences, rather than ratios, then gauge works because the difference in gauge is equal to the difference in absolute.

>>7029091
7/10
Subtle

>>7033093
only a sith deals in absolutes.

>>7032726

Egad, what a blunder.

>>7033340
>Darth Boyle

>>7032726
>gauge versus absolute
>Celsius versus Kelvin
only one person gets it