It is quite hard to explain it in layman terms, I agree. But if we can't even discuss that, then it's (even more?) meaningless trying to debate this over the NIST. I hold my position, that we should try to understand it as best as basic physics allow us to.
Very good! Let's apply basic physics. First of all, how much of the plane's energy was lost when it entered tower (the question applies to both towers)?
To calculate the initial force, we would use Newton's good old mass times acceleration. The acceleration, in the case, is the amount the plane slowed down when it initially hit the tower (I know it's counterintuitive to think of slowing down as being "acceleration", but in physics terms, any change in velocity is acceleration).
Without doing any complex calculations, it is easy to see from videos of the second crash that the acceleration -- at least initially -- was relatively small, because the back of the plane entered the building at close to the same speed as the front. This tells us that the mass of the plane still had a LOT of energy after passing through the perimeter.
Of course, by "the mass of the plane", I don't mean the plane was in one piece. It seems that way by looking at it, but it was shredded as soon as it passed the perimeter. So, each piece of the plane had less momemtum than the whole, but the TOTAL momemtum was not significantly changed in the first couple of milliseconds.
Some of the energy of the crash was lost disassembling the plane, and more was lost when these pieces of the plane wreaked holy havoc on the inside of the building. However, when you consider that the forces involved were many, many times greater than either the airliner or office furniture/cubicles/sheetrock were designed to withstand, then it's not surprising that the individual pieces would have retained a great deal of energy.
(Don't believe me? Try kicking a hole in an office wall. Now imagine if your foot was made of metal and moving at hundreds of mph.)
So, what WAS designed to withstand such forces? The steel frame, of course. Not by making each individual beam indestructable, but by allowing the mass of the building to be redistributed to intact columns as some beams were destroyed. Those steel components that survived the crash would have stopped the flying debris cold, and here is where the force was greatest, because the acceleration (change of velocity) was greatest. It's easy to see, then, that the columns that survived were the ones that absorbed the greatest amount of energy, and therefore would have been the ones most likely to lose the fireproofing insulation in the crash.
So, we have:
1. An airliner that didn't slow down much as it entered the building, and therefore retained a great deal of energy,
2. A building made of some materials that were not designed to withstand high-speed collisions and could not have slowed the pieces down by much, and some materials that were designed to withstand such collisions and would have stopped many of the pieces,
3. These same materials (the steel in the frame), though resistent to collisions, were vulnerable to fire, so had to have fireproofing insulation,
4. The beams which survived the initial crash became the ones most vulnerable to fire, because they absorbed the greatest forces and lost their insulation.
Of course, this would be more precise with at least crude calculations, but logic can carry us pretty far here. The calculations were, in fact, done by those more qualified than I, and if they are satisfied with the conclusions, then so am I.
) to reach the trusses in such a way to dislodge it. Many variables are contained within this factor, and some will probably remain unknown unless there's some piece of text within the NIST which successfully analyzes all this. this will remain unset until someone posts something, or I get to work and search for it myself.
