Originally Posted by DGM
It is the structure of the mass representing PE that matters. Examples:
1. Pour 30 000 tons of water (plenty of PE) on WTC1 and WTC1 deflects the water and the PE ends up in the gutters of NYC. Agree? Water is not very rigid!
2. Drop an ice block of 30 000 tons (same amount of PE) on WTC1 and the steel columns of WTC1 will break the ice and the PE ends up as small ice blocks in the streets of NYC. Agree? Ice is slightly more solid than water but not rigid! Don't you break ice and put it in your G&T at 5 pm?
3. Drop the top part of 30 000 tons of WTC1 on the WTC1 structure below and the top part breaks up and pieces of it falls down on the plaza below while some remain up top - actually bounces on the structure below. Reason? Top part was not rigid. No collapse will ensue due to PE>SE.
4. Drop anything A on anything B and see Newton's third law at work. A cannot free fall through B (even if NIST suggest that that is the case with WTC7).
Physics is not difficult. But structure of material matters. It seems you are stuck in la-la land wherever it is.