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The Physics of Natural Football Deflation

Discussion in 'Fred's House of Pancakes' started by SageBrush, Jan 21, 2015.

  1. bisco

    bisco cookie crumbler

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    bad news, the national media has moved on from deflate gate to the megasonic bionic superstorm of the century about to hit the northeast. could be the end of the world as we know it. i hope the pats are already in arizona.
     
  2. fuzzy1

    fuzzy1 Senior Member

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    But the 2 psi loss is less than 10% (more like 7%) of the absolute pressure.
     
  3. wjtracy

    wjtracy Senior Member

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    I went to Walmart to buy a football but most were 7-9 lbs inflation - different animal.
    They had a couple Wilsons taking 13 psi but the label did not say: 3-ply VPU bladder (which the official Wilson NFL footballs have). So I did not get one.

    Anyone know what the heck VPU is? Google has no idea what that means as it pertains to acronyms. It's a Wilson patented bladder material, but apparently only Wilson knows what VPU means?
     
  4. Chuck.

    Chuck. Former Honda Enzyte Driver

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  5. wjtracy

    wjtracy Senior Member

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    oops Bill Nye is Sea Hawks fan so be careful there.
     
  6. bisco

    bisco cookie crumbler

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    video pulled.^^^
     
  7. wjtracy

    wjtracy Senior Member

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    Maybe Bill Nye was wrong, which would be bad for his rep.
    Can you imagine how many people (news orgs, etc) are out there rubbing footballs to see what happens?
    I'd have done it already if I had a official NFL football, or even a close facsimile.
     
  8. SageBrush

    SageBrush Senior Member

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    Interesting point.

    If we had removed the same amount of air using an absolute pressure gauge, how much would the psi have dropped ?

    Why would it surprise anybody that friction generates heat ?

    Although Belichick did not explicitly say so, I got the impression that they measured pressures of the football at key points during their trial run-throughs for the NFL investigation. I presume that is how they know that the ball gained one psi at the end of the massage.
     
  9. wjtracy

    wjtracy Senior Member

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    My orig post gave the number as 1 gram for every 3 psia

    Empty ball weighs in at 420 grams or so

    Re: above
    Right, I agree Bill Nye said rubbing could not do it. So now climate change is in question too.

    I thought Bellichick's press conf was more or less admitting what they do impacts the pressure up to several hour he said
     
  10. SageBrush

    SageBrush Senior Member

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    Fuzzy is right -- a 2 psi drop in pressure is ~ a 7% drop in amount of air in the ball. This is the second time I have make this error in this thread :mad:
     
  11. wjtracy

    wjtracy Senior Member

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    ^^^right and also some comment about engineers was thrown in too as I recall
     
  12. bisco

    bisco cookie crumbler

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    so where do we stand?
     
  13. SageBrush

    SageBrush Senior Member

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    The comment about US measurement units STANDS :)

    7% of (1.25 grams per liter * 4.2 liters) is so much easier.
     
  14. wjtracy

    wjtracy Senior Member

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    The $64000 question is how the footballs are prepped for the big game.
    I recommend the following:

    (1) Need affidavit that the balls are orig, no new laces, no new bladders, and approx age of balls; record ball serial no. weight, Psig
    (2) Give 15 balls to refs 24-hrs before kick off; hold 3 as retains
    (3) Refs immediatlety depressure balls and fill with dry air or N2 three times to 13.5 psig
    (4) Finally set pressure at regulation 13 psig day before game.
    (5) Morning of Game - Pressure reset to 13 psig
    (6) Each ball gets one stiff punt from the 3rd string punters or FG ki ckers
    (7) Measure any fall-off in pressure discard balls floating on pressure
    (8) 2hrs before game recheck and discard balls with pressure falling out of ordinary
    (9) Game Time - Refs picks ball - I assume Brady want to picks balls that have lost pressure by his touch. He only needs one low P ball to sneak thru.
    (10) Half Time P check

    I think what Belichick informed us in layman-science terms, is that football pressuring has multiple steady states. The steady state Pressure you get depends on the trajectory of how you got there. For example, if you reduce pressure, tighten the laces, and very carefully and slowly increase P to 12.5. It may stay at that steady state until a 400-lb lineman falls on it, and then puff we got a 11 psig ball due to loosened strings.
     
    #74 wjtracy, Jan 26, 2015
    Last edited: Jan 26, 2015
  15. bisco

    bisco cookie crumbler

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    they're reporting that only one ball was 2 psi low, the other 10 were closer to 12.5 but still low. no details and no idea where the info is coming from.
     
  16. fuzzy1

    fuzzy1 Senior Member

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    Yesterday I got the impression that he spoke much too hastily, based on his hometown roots, without fully engaging the brain.
     
  17. SageBrush

    SageBrush Senior Member

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    If he wasn't just joking, he was (I suspect) just differentiating between air removal and a pressure drop.

    All else being equal, air removal will drop the pressure, while
    pressure can go down unrelated to air removal.

    Or... he was being a bit foolish and giving his opinion of why the pressure dropped by halftime.
     
  18. GregP507

    GregP507 Senior Member

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    I don't think I'm the only one who thinks it's incredibly anal to expect someone to keep a football inflated within 2 psi of a particular standard. It's hard to imagine that such a minor change could favor one team over the other.
     
  19. SageBrush

    SageBrush Senior Member

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    Belichick reported that when his quarterbacks were asked to identify balls that had been deflated 2 psi, they were right 50% of the time.
     
  20. wjtracy

    wjtracy Senior Member

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    If the quarterback is allowed to sort thru the balls (which I do not know if he is) he only needs one

    Radio says person of interest has emerged. The refs apparently did not keep the chain of custody...balls go back to the team for "whatever" after the initial P-check. Sheesh. The simple explanation is of course letting air out.