Re: DATA on collapsing WTC

["Glenn A. Carlson" <gcarlson@CHUCK.STCHAS.EDU>]

I've posted my graph of the position v. time data including best fit power
law curves.  http://www.stchas.edu/faculty/gcarlson/physics/wtc/index.htm

I'm getting very different results.  For all the data (start of collapse =
0 s), I find that the tower is nearly in free fall, but during the first
second the tower is falling at nearly a constant speed.

It seems reasonable to me that early in the collapse the tower might not be
in free fall, because the lower intact structure would exert an upward
force on the falling floors.  But later in the collapse as the falling
floors gain momentum (more floors and more speed) any upward force from the
intact structure would have a negligible effect.  The building would fall
as if the lower floors were not even there.

Glenn

At 02:00 AM 9/19/01, you wrote:
> Date: Tue, 18 Sep 2001 22:04:27 -0400
> From: Ludwik Kowalski <kowalskiL@MAIL.MONTCLAIR.EDU>
> Subject: Re: GLEN'S DATA on collapsing WTC
> MIME-version: 1.0
> Content-type: text/plain; charset=us-ascii; x-mac-type=54455854;
>  x-mac-creator=4D4F5353
>
> There is something suspicious with data I used to get the second
> line of my table. Perhaps it was my clerical error, I will check it
> later. Everything else looks good. The v versus t plot is not a
> straight line. As one might expect the slopes fluctuate, reflecting
> what was happening below. At t close to 1.1s the acceleration
> was nearly constant and large (7 m/s^2) but at t close to 2.6 s it
> was nearly zero. The overall acceleration (the best straight line
> through all points was about 2.7 m/s^2. At no time was it a free
> fall because the acceleration was never larger than 7 m/s^2. In
> other words, the net force down was never as large as m*g.
>
> Ludwik Kowalski wrote:
>
> > SEE MY TABLE BELOW.  FIRST I WANT TO THANK
> > Glenn A. Carlson,  [from St. Charles Community College,
> > St. Peters, MO  USA] for sharing his digital data on the
> > collapsing tower with the list; and for allowing us to use the
> > data, noncommercially. I am sure that many physics teachers
> > will appreciate what he did. Glen's e-mail address is:
> > gcarlson@chuck.stchas.edu
> > ***************************************
> > For convenience I decided to group data into sets of nine
> > frames. For each set I calculated the mean distance and
> > converted it into meters. I ignored the first 9 frames;
> > but "invented" the first line (y=0 at t=0). Is it OK?
> >
> > For many of us averaging nine distances is acceptable.
> > In my table times are as specified by Glen for the middle
> > frame of each set. Do not take all the digits shown as
> > significant; I prefer to exaggerate. The last line in my
> > table is from the set of last 6 frames.
> >
> > Here is my table:
> >
> > t (s)         y (m)
> > ********************
> > 0.000         0.000
> > 1.108        -1.561   <-- Here I must look at Glen's data again
> > 1.712        -3.444
> > 1.981        -5.359
> > 2.283        -8.577
> > 2.585       -13.245
> > 2.887       -17.839
> > 3.189       -23.505
> > 3.491       -29.630
> > 3.760       -35.129
> > 4.062       -42.110
> > 4.331       -48.541
> > 4.633       -54.059
> > 4.884       -61.215
> >
> > Ludwik Kowalski

------------
Glenn A. Carlson, P.E.
St. Charles Community College
St. Peters, MO  USA
www.stchas.edu/faculty/gcarlson/physics
PGP Fingerprint  E88D 2AB8 C5A8 D231 06B9 1597 3C72 5CC2 7D87 5519
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