I just came across something that might be of interest to you. It is a

paper by a "Dr. Frank Greening" here:

http://www.911myths.com/WTCREPORT.pdfIn it, he attempts to calculate the feasibility of the collapse of the

towers but I believe I have found an error.

Here he states:

we have an initial mass nmf

falling onto the

floor below and becoming mass (n+1)mf. This new, enlarged, block of

floors descends

with velocity v2 = {n/(n+1)}v1 through a distance hf at which point it

strikes the floor

below and becomes mass (n+2)mf moving at velocity {n/(n+2)}v2, and so on

The problem is, in a hypothetical tower collapse, the only thing that

would change is the velocity of any mass above the collapse points. The

total mass would not change. If he

wants to add the mass of each floor to the upper mass with each

collapse, that is fine but he also has to then subtract the same mass

from

the lower floors.