Comment: Conservation of Momentum is the Appropriate Rule Here

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Conservation of Momentum is the Appropriate Rule Here

F=ma always applies; however, the conservation of momentum is a derived form of that equation which states m1v1+m2v2=m1v3+m2v4 where velocities of the moving bodies can be determined before and after a force is applied.

In the case of the "pancaking" theory the mass coming down would be slowed by the stable mass of the structure below it. It would necessarily be impossible (newtonian physics) for a structure to freefall and pancake.

Per the rest of your argument, I don't really know the answers. The only thing I would say is that the twin towers and building 7 did NOT pancake down. They were effectively in freefall. Why they were in freefall is for someone above my pay grade. Cheers.