asphalt and bedrock are poorly compressible but so is concrete...and steel doesnt compress and turn into chuncks or pieces. Steel buckles under compression. It doesnt simply turn into chuncks of I-beams.
You migh be right about the coliding portions crushing everything but if u do a quick calculation based on the FREE FALL, which means there is NOTHING in the way even air is excluded, and the floor heigt is 13'4" so that would comeout to be 20.537 mph not 40 or 50. Now lets put some steel and concrete in the way and im quit sure that the speed is going to reduced significantly.
If we say that thats how they fell down then the collapse of the building would slow down foot by foot due to the loss in kinetic energy when it collides of the floors below that HAVE NOT been touched by a single flame. It juslt like when you play pool, you hit the cue ball and when it collides with the other ball it transfers some kinetic energy, therefor it slows down but it makes the other ball move but as at slower rate than the cue ball. Based on that FACT that you can observe when you play pool we can conclude that those top 30 floors that fell down onto the building would keep on slowing down no matter what kind of material is in the way, even if you put wood in the way it would still slow it down and inch by inch you can calculate the deceleration. What if you put steel and concrete in the way? It is impossible for an object thats moving at speed to collide with something and keep moving at the same speed.
You can observe that the buildings are falling at a constant rate from the top to the bottom, which is a big problem here.
For mr. mindphuck
my original freefall calculation (9.2 s) did not even deal with wind resistance, its hard to even calculate the wind resistance but it can be done. What we know is 9.2s is the time it would take for an object to fall to the surface of the earth from 415m with out air underneath.
Again, lets put something in the way such as air. The time would increase, how much it increases you can work the math out yourself but it would add around 2seconds due to the shape of the cross sectional area of the floors. Put some more material such as I-beams, Trusses, which you can google how strong they are (try the crane booms), concrete, office supplies and all that you can think of. Based on that im sure and i know that if it was to fall naturally due to the heat or whatever the time is going to increase and it would surpass your 14-15 second window by a lot.
and please if your going to present something as fact OR argue with my numbers, go do some math your-self and then compare your results with mine. and if anyone has a problem with the simple equations i used please let me know