Oops 2.0. This is what happens when I rush and don't check my work.
70F = 21C 40F = 4.4CP1 = 12.5 PSI T1 = 273 + 21C = 294K T2 = 273 + 4.4C = 277K
Calculated P2 = 11.8 PSI Pressure drop = 12.5 - 11.8 = 0.70 PSI
Looks like the other JL is correct.
Thanks.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
You guys are getting closer. Now there is one more thing that you are forgetting.
Dan
You need to use absolute pressure.
-- ----Android NewsGroup Reader---- http://usenet.sinaapp.com/
** Relative pressure is very annoying.
Especially from in-laws....
.... Phil
Right. That makes the drop more like 1.56 PSI.
ESPN reports that 11 of 12 balls were 2 PSI below the legal limit of
12.5.-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Should the pressures be gauge or absolute?
Sigh. I can't believe I screwed it up this badly. This is basic stuff. 4th try is the charm (I hope).
70F = 21C 40F = 4.4C P1 = 12.5 PSIG = 27.2 PSIA T1 = 273 + 21C = 294K T2 = 273 + 4.4C = 277K Calculated P2 = 25.6 PSIA Pressure drop = 27.2 - 25.6 = 1.60 PSI which makes the Prominent Boston Physicist correct.Just for fun, converting back to gauge pressure: 25.6 PSIA = 10.9 PSIG Pressure drop, as measured by the gauge on the pump: 12.5 - 10.9 = 1.6 PSI
Double checking: P1/T1 = P2/T2 P2 = P1*T2/T1 = 27.2 * 277/294 = 25.6 PSIA Ok, that works.
Enough. Gone sulking...
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
defeat-deflategate.html
Yes. Being elastic, the bladder/ball/entire containment actas as a spring for a small period of the deflation. Once past a certain point, however, it also relaxes, because it is not like a deflated balloon, where the expansion is several tens of percentage points.
Nice catch. The effect may be less than you equated due to the relaxation point not being very far from a mere couple pounds off "full". IOW, you may have given it more spring than it actually has.
defeat-de
Should also fill the ball, and let it all settle to the declared temp.
As you fill, the air you fill with will NOT match that of the tank it escapes from, nor the wall temp of the bladder you fill with it.
A direct reading at the start of the experiment is needed. That has to be quite a while after the actual fill, and after it rests in the temperate environ the test presumes to be taken under.
The subsequent reading must be taken AFTER the ball has had settling time at the new temp as well.
Also, what is the effect caused by a severely overinflated (seam stretching) of the ball, then relax it. Do the experiment the next day. I'll bet the bladder has less "spring" tension against it then.
Does a previously "wetted" ball have leather shrinkage issues?
That's not right either. If the pressure inside the ball was only 12.5 PSI it would look more like a warped pancake. The formula uses absolute pressure, not relative. You need to add in the ambient air pressure to get absolute pressure, do the math and then subtract ambient back out before you compare to the starting relative pressure.
Keep in mind that ambient will vary with altitude and less so with weather conditions. Denver average pressure is about 85% of sea level air pressure. 14.5 psi at sea level and 12 at Denver... not that they were playing in Denver, but the proper ambient pressure needs to be considered when you do the math.
-- Rick
Nice in what way? He completely messed up the equation by using the wrong pressure and once the ball is inflated enough for the bladder to fill the ball, it is no longer very elastic since the size of the ball will change very, very little.
I see that someone got the math right at least.
-- Rick
defeat-de
The calculation should be from absolutes.
This should be able to be extrapolated upon real world gauged readings.
Because of your well earned reputation as a know nothing troll, what you call anybody is totally irrelevant, just as you are totally irrelevant.
so....the gambling community believes that the Pats will win, eh? That's why they have to trot out this absolutely 'upsetting to' Bradley claim that HE did something wrong.to take his edge off the game.
[If each club fills their own footballs, allowing that and then getting inaccuracies is completely the fault of the commission,] Some of my observations:
Oh finally someone else ran the numbers.
70 F (fill temp.) = 21 C = 294 K 40 F (play temp.. I thought it was 50 F at gaime time.. but no matter) 40 F = 4C = 277 Kratio = 277/294 = 0.942 (x12.5 = ~11.8 psi.) That Pats are still cheater's. And Mike Naughton (the boston prof.) should know better. (I knew him at UB, I'll send him an email...)
(of course being a Buffalo Bills fan I totally hated the Pat's already.)
George H.
(Note to self read the entire thread before responding...) Adding the 14.7 psi I get 10.9 psia at 40 F.
N2 for tires is comforting if you find yourself having to use a tire inflator can sometime. Since the Freon ban, they're pressurized with butane.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
for while (until it was banned) the F1 teams used r134a to inflate the tires because it kept a more constant pressure
it's weird that you can buy stuff that is meant to be vented into the air, like airhorns or the non-flamable freeze spray, filled with r134a
but buying a can of r134a to fill an aircon is no go
-Lasse
My, that was a HOT kick...
Kahn Academy video on deflategate (8:56) Spoiler: 5% drop in temperature, 7% drop in pressure.
-- Jeff Liebermann snipped-for-privacy@cruzio.com
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