Like Bazant, you have athe top part destroying the building below but not being destroyed itself. That is a violation of Newtons third Law: For every action, there is an equal and opposite reaction. In a gravity collapse, the top part of the building would be destroyed at the same rate as the building below.
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This has been hinted at before, but not been explicitly denied:
No! Wrong! Most emphatically: FALSE!
Newton's Third Law does NOT say, nor imply, nor predict, nor anything, that colliding structures will be destroyed at the same rates!
"Destruction" or "Rate of Destruction" is neither the "action" nor the "reaction" that any of Newton's Laws speak of.
This is a total perversion of Newton's Laws.
Unmitigated nonsense.
I know it is a favorite "argument" that has been made by Truthers for many years - but each time a Truther made it, they made an HUGE error. The popularity of the argument, and the fact it has not been exposed as stupid, perhaps even fraudulent from within the Truth Movement, is testament to how the TM stubbornly insists in being wrong and is incapable of correcting their countless errors.
I strongly advise you to purge this crap from your brain and never use it again.
(The "falling" and the "standing" structures that collided at the WTC collapses were not equal to begin with: One was more massive and coupled to planet earth, the other smaller and free at the other end. Also, one was tilted with respect to both the force vector of gravity and the direction of motion, the other was not, making the tilted part more vulnerable and thus prone to a higher "rate of destruction".
But as soon as collapse had begun to destroy stuff, things really developed apart: A layer of compacted debris accumulated, and it traveled with the falling part: The differential velocity between falling top and accumulating debris layer was next to zero, while the differential velocity between standing top and accumulating debris layer was substantial and greatly accelerated. Thus, the bottom part was immediately hit by a massive, growing, ever faster compacted debris layer - and the top was not. THAT is why the bottom surely disintegrated faster than than the top - and why the "equal and opposite" lore becomes a layman's fantasy fractions into the collapse at the latest)