h****e
发帖数: 292 | 1 http://sports.yahoo.com/news/physicist-emailed-us-explain-exact
摘要：
“In a just world, you the media, would be apologizing or get sued for
everything you own. This was obviously done with malicious intent.
Unfortunately, one of the more unjust aspects of press freedom is that the
media is shielded from being sued by public figures. That leaves the media
free, except by their own restraint, to lie, sensationalize, and slander. ”
------------------------------------------------------------------------
Dear Sir,
As a physicist, and having listened to Belichick's press conference earlier
today, I can tell that what he said made a lot of sense from a scientist's
point of view.
When the football is rubbed and squeezed, work is being done on the ball,
and it will get hotter. If you want, describe the heating as due to
friction. When the rubbing stops, the ball will cool back to the
environmental temperature. The time constant for cooling depends basically
on the materials used in the ball, but pigskin is likely a very poor thermal
conductor, which would mean longer times, other things being equal.
The air inside the ball, only a few grams in weight, will equilibrate with
the walls of the football quite rapidly — seconds.
If the ball is still warmer than the environment when given to the referees,
then they will be deflating the ball back to the requested 12.5 psi. By the
way, just inflating the ball with a pump adds some heat to it. That is
because the air is squeezed until the pressure in the pump is higher than
the pressure in the ball before the air goes into the ball. The squeezing
heats the air, quite a bit, but the air doesn't have a lot of mass.
So, now when the ball equilibrates with the environment, by cooling, the
pressure will decrease, according to the Ideal Gas Law, particularly if the
environment is significantly less warm than the environment where the ball
was inflated and then checked by the referees. Obviously, it was a lot
colder on the football field, and got even colder later in the evening.
This scenario, in my professional opinion, completely explains the data that
has been reported.
Differences with the balls used by the Colts could easily be explained by
different preparation procedures, or even longer waits between preparation
and the referee check. Especially if the the Colts QB, Luck, likes higher
initial ball pressure — as has been reported.
Now, I have something bad to say about the media. You pinheads have been
convicting Belichick and Brady without the facts or doing an investigation.
Some of you have even gone so far as to demand the Patriots be disqualified
from the Super Bowl. Others have called Brady and/or Belichick a liar.
One of your colleagues at BI, Tony Manfred, is a prime offender.
In a just world, you the media, would be apologizing or get sued for
everything you own. This was obviously done with malicious intent.
Unfortunately, one of the more unjust aspects of press freedom is that the
media is shielded from being sued by public figures. That leaves the media
free, except by their own restraint, to lie, sensationalize, and slander. I
have been noticing less and less restraint by the media.
At the bottom of this message is a simple calculation on the ball pressure,
just moving it from inside to outside that I did a few days ago. It is
consistent with the study that the Patriots did, but Belichick's press
conference provided new details that validated my position even further.
Have a great day!
Sincerely,
Kirk
Kirk E. Hackett, PhD
Physicist
I wrote the following last Wednesday:
There has been a fair amount of bad comment about whether temperature can
account for the observed football deflation in the AFC Championship game.
Many of the calculations just use the pressure measured by a gauge on the
ball, but this is a mistake. You need to account for the fact that the
measurement is a gauge measurement, not an absolute measurement of pressure.
This is the argument:
If the balls were initially inflated to 12.5 psi (the minimum) in a locker
room at 75 F, then the pressure inside the balls at 45 F (like at halftime
on the field) would be about 11 psi — already down by 2 psi from the
nominal 13 psi inflation pressure. The calculation is trivial, uses the
Ideal Gas Law, the fact that the pressure measurements are gauge
measurements (relative to the base atmospheric pressure, (I used 14.7 psi
for the base atmospheric pressure)), not absolute pressure measurements, and
assume the football volume doesn't change.
Additionally, each pressure measurement takes a little air out of the ball,
and multiple measurements can also significantly reduce the pressure.
Cyclists understand this.
Given the multiple pressure measurements that were made, plus natural
leakage due to rough play, plus temperature differences, all this could very
easily result in more than a 2 psi pressure drop, measured at or near field
conditions.
Here are the numbers:
75 F = 297 Kelvin (Need to use absolute temperatures)
45 F = 280.4 Kelvin
280.4/297 = the absolute pressure ratio = (X +14.7)/(12.5 + 14.7)
Where X is the gauge measurement of the ball pressure at the field
temperature, 45 F.
X = 10.98 psi.
2 psi less than the nominal 13 psi. Just from temperature differences.
There have also been reports that the balls weighed less. Ridiculous. Air
doesn't weigh much. You would have to weigh the balls to a couple of tenths
of a percentage, and you couldn't do that by just hefting the balls.
Why don't you report this and send it along to the NFL, too. It sure would
be good to shut up the ESPN sensation mongers.
The NFL should do a real technical analysis, and some experiments.
Cheers,
Kirk
Kirk Hackett, PhD
Physicist | W*****d
发帖数: 4196 | 2 各位大牛，奥赛金牌，top N的高材生来批批这位民科的物理吧，
别忘了喊上小k 老师 | B******r
发帖数: 612 | 3 小k没事就自我高潮好多次，更何况这次总算有人和他一起自摸，精虫上脑，挡不住的 | p*******e
发帖数: 2310 | 4 Rule of thumb in real life: when temperature drops 20 F, your tire will lose
about 1 psi pressure.
读过十万个为什么的中国土球迷难道连这个道理都不知道？？ | t********t
发帖数: 5415 | 5 rule of thumb不能当science用啊，问题从来就不是气压，而是NE是不是故意放气
lose
【在 p*******e 的大作中提到】
: Rule of thumb in real life: when temperature drops 20 F, your tire will lose
: about 1 psi pressure.
: 读过十万个为什么的中国土球迷难道连这个道理都不知道？？
| B******r
发帖数: 612 | 6 其实说来说去最早爆料的ESPN那个逼货也没错，球压的确是低于12.5， ''under
inflated'',但这二逼为了炒作搞大标题，完全不考虑降温这些自然因素，还带扣子躺
枪。
不过由这事可以看出，pats在全美媒体眼中甚至包括了NE当地媒体眼中的形象。这几天
我tweet基本把weei 和boston local sports骂了一个遍，当全世界都针对我们时，至
少我们自己人应该团结。 | y****q
发帖数: 94 | 7 什么叫做“问题从来就不是气压”？给点逻辑？
【在 t********t 的大作中提到】
: rule of thumb不能当science用啊，问题从来就不是气压，而是NE是不是故意放气
:
: lose
| t********t
发帖数: 5415 | 8 联盟想知道的是气压低是因为非人为原因（天气/外星人/等等）还是拍子故意放低的（
不论是送检之前还是之后），如果因为非人为原因气压低了那只能怪老天。擦边球？是
。违规？不是。
【在 y****q 的大作中提到】
: 什么叫做“问题从来就不是气压”？给点逻辑？
| l*******b
发帖数: 782 | 9 同是拍饭，这物理phd的科学家无论气度，严谨程度都跟白神差太远了
而且到底拍子的球少了2psi是比下限少的还是比要求的中值少了
按他的计算11是正常的是建立在中场测在室外温度的假设上，这个本来就不一定对，
何况扣子的球没亏气，球不都是主场的球童管的吗，扣子可不敢在客场作弊吧。
earlier
【在 h****e 的大作中提到】
: http://sports.yahoo.com/news/physicist-emailed-us-explain-exact
: 摘要：
: “In a just world, you the media, would be apologizing or get sued for
: everything you own. This was obviously done with malicious intent.
: Unfortunately, one of the more unjust aspects of press freedom is that the
: media is shielded from being sued by public figures. That leaves the media
: free, except by their own restraint, to lie, sensationalize, and slander. ”
: ------------------------------------------------------------------------
: Dear Sir,
: As a physicist, and having listened to Belichick's press conference earlier
| r*******d
发帖数: 2413 | 10 I'm disappointed in Dennis and Callanhan from weei.
【在 B******r 的大作中提到】
: 其实说来说去最早爆料的ESPN那个逼货也没错，球压的确是低于12.5， ''under
: inflated'',但这二逼为了炒作搞大标题，完全不考虑降温这些自然因素，还带扣子躺
: 枪。
: 不过由这事可以看出，pats在全美媒体眼中甚至包括了NE当地媒体眼中的形象。这几天
: 我tweet基本把weei 和boston local sports骂了一个遍，当全世界都针对我们时，至
: 少我们自己人应该团结。
| x****u
发帖数: 12955 | 11
If NE deliberately lowed pressure after referee measured it and before they
took the ball to the field, then the pressure measured at half time would
have been even lower than around 10.5. Say they pumped it to 12.5 before
ref measurement, lowered it to 11.5, then after cooling down and gotten wet,
the half-time measurement would have been somewhere around 9.5psi.
The 10.5 psi number is within the realistic possibility given what we know
happened to the ball.
【在 t********t 的大作中提到】
: rule of thumb不能当science用啊，问题从来就不是气压，而是NE是不是故意放气
:
: lose
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