North Tower Acceleration

[cpwm17]

9. Try this analogy

Place a 10lb weight on top of a 1ft stick that is capable of supporting 20lbs without buckling and breaking - so far so good.

Now lift that 10lb weight 1ft above the top of the stick, and place it on top of another similar stick connected to the first stick. The weight will be 2ft off the ground now. Now break the top stick, which will drop the 10lb weight on top of the lower stick. What do you think will happen?

The weight will accelerate through the lower stick and break it. The weight will hit the ground a little slower than if the lower stick wasn't there at all - let's say at 90% of free fall speed. The 10lb weight would then average .9g acceleration

By David Chandler's logic, the lower stick only provided .1W (1lb) resistance, which means that the weight only provided .1W (1lb) of worth of force. Since 1lb is 90% less than 10lbs, the lower stick must have been broken by some other means - perhaps an explosion.

He then goes into some nonsense about its constant acceleration - and whatnot.

My analogy isn't perfect. As the towers collapsed, the falling sections gathered more mass from the lower sections of the building as they fell. The mass from the lower sections of the buildings started at an initial zero velocity, which slowed down the acceleration of the falling sections.