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Re: GLEN'S DATA on collapsing WTC

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