North Tower Acceleration

[cpwm17]

41. Expulsion of matter is much greater for larger, taller buildings

As you scale up the size of any object its strength to size (and mass) ratio goes down. This means that there is a lot of stress on large, tall buildings. So during a collapse of a large, tall building, depending on its construction, there is a lot of potential for a rather violent collapse. The towers weighed around 500,000 tons. There is a lot of potential energy being converted to kinetic energy during the collapse. That's the energy of a very large bomb.

The only way for there to be any deceleration during the collapse would be for the resisting force of the intact section of the lower block to be greater than the force of the falling upper block striking the lower block. That certainly didn't happen during the collapse. The lower block only slowed down the acceleration of the upper block's mass. The force after the upper block's mass fell a dozen feet between the floors is far greater than the resisting force of the intact section of the lower block. So it must accelerate all the way down, especially after the debris between the blocks increases during the collapse which provides more mass to accelerate the collapse.