Reply #143: Please read my post #8 again

[janedoe]

Pay careful attention to "Case 2."
Pay careful attention to the concepts.
http://www.democraticunderground.com/discuss/duboard.ph...

Once you've reviewed that, consider the chart below.


Let's say that we want to collapse the entire building in the time it takes for free-fall of the top floor of WTC1. (Use 9.2 seconds as the time it would take the blue ball to drop from the roof to the street below, in a vacuum.) So, if the entire building is to be on the ground in 9.2 seconds (in a vacuum), the floors below the "pancaking" must start moving before the "progressive collapse reaches that floor, below. To illustrate this, use the concept of the billiard balls. If the red ball (100th floor) is to reach the ground at the same time as the blue ball (110th floor), the red ball must be dropped 0.429 seconds after the blue ball is dropped. But, the blue ball will take 2.779 seconds after it is dropped, just to reach the 100th floor in free fall.

Case 2, in my earlier post, shows the red ball being dropped just as the blue ball passes that point.

Remember, I'm assuming the building was turning to dust, as the collapse progressed, which is essentially what happened.

So, for the building to be collapsed in about 10 seconds, the lower floors would have to start moving before the upper floors could reach them, by gravity alone. Did we see this? I believe it's pretty clear in some of the videos. The "wave" of collapse, progressing down the building, is moving faster than free-fall speed. This would require something like a detonation sequence.

Realizing that, for example, the 40th floor needs to start moving before any of the upper floors have "free-fallen" to that point, why would it start moving? There was no fire there. And, if anything, there is less load on that floor as the upper floors turn to dust.