Punted Football
Punted Football
(OP)
Yesterday I took a tour of the new Dallas Cowboy stadium and it is an engineering marvel. Above the field is a mammoth 4 sided scoreboard/screen, the bottom of which is 90 feet off the playing field. (Its length extends from 20 yard line to 20 yard line)
There is debate as to whether that is too low and may be hit by punts. I've read that the average hang time for an NFL punt is 4.6 seconds. To calculate the height I used the following reasoning, does this seem sound?
Discounting aerodynamics, a punted football will follow a parabolic arc, with exactly half it's time traveling upwards, and the other half downward. That's 2.3 seconds going up and 2.3 seconds going down.
Using the formula y= (0.5)(32.2 ft/s sq)(time squared). I calculate the average height based on average hang time is 85.2 feet. A hang time of 4.73 seconds and above translates toa punt 90 feet and higher height.
Does this seem correct?
There is debate as to whether that is too low and may be hit by punts. I've read that the average hang time for an NFL punt is 4.6 seconds. To calculate the height I used the following reasoning, does this seem sound?
Discounting aerodynamics, a punted football will follow a parabolic arc, with exactly half it's time traveling upwards, and the other half downward. That's 2.3 seconds going up and 2.3 seconds going down.
Using the formula y= (0.5)(32.2 ft/s sq)(time squared). I calculate the average height based on average hang time is 85.2 feet. A hang time of 4.73 seconds and above translates toa punt 90 feet and higher height.
Does this seem correct?





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I know it neglects friction and the aerodynamics of the football, but it would probably be a reasonable estimate of the flight path.
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Initial velocity and launch angle determine the horizontal range and hang time of a punt, with a significant dependence on air resistance resulting from various spins on the ball. Air resistance reduced distances of punts by 24-33% and had a nearly negligible effect on hang times estimated from simple equations for projectile motion. The equations of motion provide a reasonable approximation for hang times, but need to include air drag factors to accurately model distances.
http://www.wooster.edu/physics/jrIS/Files/Ryan.pdf
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RE: Punted Football
Your assumption is a classic mistake made by engineers to make the calculations easier and eliminate the real world. Assumptions may lead you to the calculated result you expect.
Neglecting aerodynamics for an object traveling through the air is wrong, but it makes it fit idealized engineering formula if nothing else is considered. That is if the temperature is neglected.
It may be close for a round baseball (neglecting similitude and shape factors).
A football is a different shape and has different properties when propelled. The spin is one of the aerodynamic properties neglected in the interest of simplicity.
A football does not always travel in a smooth predictable path (according to equations) and it may even go end-over-end. Have you ever observed a punt "turning over" in its arc as its speed, orientation and aerodynamic properties change in an attempt to control the impact angle and the following roll.
A satellite is easy to predict because there is in an essential vacuum and only momentum and the gravity of surrounding masses.
For a football, you need a bigger computer and a more realistic parameters or just hire a punter to do everything he can do to provide some of the practical outer limits.
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bimr above found an actual study of punts, comparing equation predictions to real world results. They found that HORIZONTAL distances are 20-30% less than calculated, however the hang time values were not significantly affected. Presumably because drag affecting the accent would similarly act on the ball during decent, a wash if you will.
In the horizontal, drag affects the net flight entirely in the opposite direction of the flight, which may explain the reduced distances but not the hang times.
An important point is that hang times are real world results; ACTUAL recorded times from professional punts over many seasons of play. The study shows that hang time isn't affected as much by drag. I would speculate then that neither is vertical height of the punt.
The average professional punt hangtime of 4.6 seconds I believe results in height of around 85 feet, irregardless of velocity, angle or horizontal distance. Once punts pass the threshold of 4.73 seconds, we start seeing heights above 90 feet.
I am looking forward to football season this year. I guess we will see if punts regularly hit this thing or not. Remember that if this does become an issue, you heard it hear first, lol.
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I will certainly watch for this during football season. I hate the cold and dry desertlike feeling of the off-season. Lol. I really like footbal even though my team hasn't done that great in a while.
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When you watch make sure you have your stop watch and a way to accurately determine the height. - The refs will take care of the distance.
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The inside height of the Seahawks new practice building features a turf to rafters height of 95 feet, with another 17 feet from the rafters to the ceiling. The Seahawks claim the height is adequate to allow players to practice any football situation, including punts and kicks, without restraint.
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Ya might wanna consider using an average of the ten longest punts of record-----------
At 74th year working on IR-One2 PhD from UHK - - -
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If you "heard" it on the internet, it's guilty until proven innocent. - DCS
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Regardless of the math involved, if this screen is as low as the one in the Superdome used to be, then someone aught to be repremanded for not doing his homework. I hope this doesn't happen.
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The screens were dropped from 100 feet above the field to 90. Then Oakland's Ray Guy hit the gondola with a punt during the Pro Bowl game.
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Yeah, it's too low! There's no good excuse for that happening.
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Dallas Stadium has a design flaw with the screen, funny thing is there is PLENTY of room to raise it. Just 15 more feet and only the most extraordinary punts could hit it.
Sure wish Jerry Jones would put me on the payroll, I'm right here in town and predicted it weeks ago.
Just remember where you heard it first guys.
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You most definetely called it and I think that pretty much gives your the right to tell Jerry, "I told you so". Unfortunately I missed the game so I didn't get a chance to watch it live but we all read about it before opeening day. Cool stuff, now if we can somehow send our posts to Jerry because based on the article I read, it doesn't sound like he wants to raise it.
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I'm not going to argue over a few tenths. I'll give you props for this one.
Did you hear Jerry Jones actually blame the punter??? Punters only kick that high in order to hit screens.
Looks like that screen is going to stay for now.
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It is more accurate is to say this is a classic mistake made by mathematicians, who have the luxury of ignoring anything based in reality should they choose.
As a double-doctorate mathematician once said to me: "The difference between an engineer and a mathematician is that mathematicians make assumptions."
p.s. holy cow this forum software is horrific. Please stop using frames...my eyes, burning.....noooooooo....
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I remember years ago when a high hit went into the 4" ventilation hole in between the layers of of the Minnesota Metrodome that was an the air supported dome (now about 30 years old). This was years after the roof successfully sustained a collapse from a snow fall/snow removal and structurally survived. Provisions were made for very unusual high high hits that hit speakers or the guy wires in many indoor and outdoor parks were incorporated into the ground rules that are common and acceptable. The ball went in and was not found until much later. The design criteria should have been based on the criteria and if other items were installed that is the responsibility of the owner/architect/interior designer. Obviously the engineer should not be responsible for the structure built low enough for the undesigned scoreboard assembly and the installed height. It is possible that a 2 1/2 " baseball could go through a 4" hole widely spaced that is 200 feet high. Mesh may have been installed and a few more holes used to make up for the minor air flow, but someone designed and approved the roof structure for all uses and cite some paragraph in the criteria intially if it was described.
The scoreboard in the new Dallas football stadium was was scheduled for a temporary removal for a short term rental for a rock concert (about $1-2 million cost).
It is just an ego situation between a football god and the real world god. Now, punters may be aiming for the known target when necessary and the length is not necessary.
Either the roof height was set out too low in the criteria or the scoreboard was installed too low.
Dick