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The Physics of Natural Football Deflation

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

  1. SageBrush

    SageBrush Senior Member

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    Need is in the eye of the beholder, namely the quarterback. A team can have a group meditation around the ball followed by a group hug for all the NFL cares, so long as the ball passes the pre-game umpire exam.
     
  2. bisco

    bisco cookie crumbler

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    i think the balls are new. someone did a good interview with several qb's, either usa today or cnn, all described their preferred process for breaking in game balls before the game. they described them as shiny and smooth, not what they wanted for a good grip.
     
    #42 bisco, Jan 24, 2015
    Last edited: Jan 25, 2015
  3. SageBrush

    SageBrush Senior Member

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    Yep, but it does not matter. Teams are allowed to do whatever they want to the balls. They become game balls if they pass pre-game ump review for quality, weight and pressure. Period. Notice that ball temp is not considered.
     
  4. bisco

    bisco cookie crumbler

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    correct. and there was a time when they could not scuff up the ball before the game. pre 1999 i believe.

    btw, i don't think filling them with an alternate gas is illegal, at least i have not heard that it is.
     
  5. SageBrush

    SageBrush Senior Member

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    The only detail none of us correctly guessed was why the ball reaches the umpire warm. Turns out to be a massaged football rather than a hot room.
     
  6. bisco

    bisco cookie crumbler

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    who knew? in fact, who knew there were rules about football weight and pressure? i always thought the league provided the balls.
     
  7. wjtracy

    wjtracy Senior Member

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    It was Brady himself who got the NFL rule changed to allow teams (quarterbacks) to control the ball preparation around 2005. Prior to that the home team supplied balls, needless to say they tended to give fresh slick balls to visiting team. The only fresh new balls are now the kickers, marked with "K". That was because the kickers were overly massaging the balls...kickers like a really soft ball with a bigger sweet spot.

    If Brady needs a vigorous massage, he can get that the day before the game. Any "vigorous massaging" of the balls 5-minutes before the Refs measure the pressure has questionable if not suspicious purpose.

    What's the process look like? 12 guys vigorously massaging 12 balls in the locker room just before the Refs get the balls? If I was Ref, I wouldn't touch those balls with 10-feet pole. I guess Brady only needs one hot ball to get through to his liking. Also he probably wants some variations in pressure, if the ambient temps goes down 10 degrees he may want to change to a different ball.

    No way will NFL allow this next year.
     
    #47 wjtracy, Jan 25, 2015
    Last edited: Jan 25, 2015
  8. bisco

    bisco cookie crumbler

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    i think they do it after the balls are brought out onto the field. i wish some intrepid reporter would post the rules, instead of being judgemental and asking stupid questions. these guys aren't worth the money they're paid.
     
  9. SageBrush

    SageBrush Senior Member

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    i like the idea of the ball having to be within say 5 F of ambient, along with the other standing criteria.
     
  10. bisco

    bisco cookie crumbler

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    why not just have the ref stick a gauge in them at every tv time out?
     
  11. SageBrush

    SageBrush Senior Member

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    Or have an offensive lineman sit on the ball and measure the deflection.
     
  12. bisco

    bisco cookie crumbler

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    newsflash: bill nye says rubbing the balls won't change the pressure.
     
  13. SageBrush

    SageBrush Senior Member

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  14. bisco

    bisco cookie crumbler

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    funny how they don't quote nye. usa today only quoted him on rubbing up the balls, not the temp and other. interesting report today that the ball boy in a regular season game (carolina?) was holding the balls in front of a space heater on the sidelines, which is illegal, and the refs went over and told him to knock it off.
     
  15. FL_Prius_Driver

    FL_Prius_Driver Senior Member

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    Next NFL scandal--Miscalibrated offensive lineman
     
  16. bisco

    bisco cookie crumbler

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    they already have that, ped's.:cool:
     
  17. wjtracy

    wjtracy Senior Member

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    Found some calcs, not sure if definitive:

    Football Vol (approx) = 4200 ccs or 1.1 Gallons or 0.15 ft3

    So 0.15 ft3/380 scf/mole x 29 MW = 0.015 lbs air = 5.2 grams at 14.7 psia = 9.8 grams air at 13 psig = 27.7 psia

    So that's only about 9.8 grams air, so if you were 3-psia short that would be 1-gram difference if deflated to 10 psig.

    Basically no impact on weight. Even if He was used just be maybe 8 grams lower.
     
  18. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Interest hypothesis about vigorously rubbing the balls. I'll have my wife test it.

    Bob Wilson
     
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  19. SageBrush

    SageBrush Senior Member

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    For scientific rigor, be sure to stick a thermistor in them. A graph is worth a thousand words.
     
  20. SageBrush

    SageBrush Senior Member

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    ^^ exhibit #1 for the abuse of engineers by the US system of measurements. Sheesh.

    Try metric:
    Air weighs about 1.25 grams per liter, so 4.2 liters weighs 5.25 grams at one ATM
    The football is inflated to almost two ATM, so the air weight is doubled to 10.5 grams

    Removal of 20% of air removes two grams of weight.