High school physics says that the government story is wrong.
WTC7 fell at free fall. (NIST says so in writing.)
Expressing this using vector calculus, it is complex, but expressing this using energy, it is simple, as follows.
Note that this analysis is so simple because (1) energy is conserved and (2) free falling is the asymptotic edge case of ways structures can fall. At the asymptote there is no wiggle room, so additional confounding complexities simply go away.
Doing any work requires energy. (1) Accelerating the building downward is work. (2) Deforming a building is work.
Falling is the conversion of potential energy into kinetic energy. The falling is free falling when the efficiency of this conversion is 100%.
Therefore, if the only energy available is the potential energy of the mass suspended at height in a force field, then when free falling there is NO additional energy to do ANY other work.
That is, when free falling, you spend ALL of the energy accelerating the mass downward; in particular, no energy remains to do the work of deforming the building.
You could say that the building fell, and then stopping falling deformed the building, but then time goes in the wrong order: you have to deform the building so that it will fall.
At the first press conference NIST gave after 9/11, someone yelled out to the head of NIST "WTC7 fell at free fall". The head of NIST responded like he was reciting something he learned long ago: "no, it can't have, because you cannot have a progressive collapse of a structure at free fall". (Above I just gave the conservation of energy proof of this statement.) (Link wanted for this interaction).
I think it was six months later that NIST published that WTC7 fell "at free fall for several seconds". It cannot fall at free fall for any number of seconds. (Link wanted for this document).
What got me into this was seeing a YouTube video of a high-school physics teacher plotting each frame of the building falling and getting -10 m/s^2, which is free fall plus a bit of fudge factor. (Link wanted for this video.)
High school physics says that the government story is wrong.
WTC7 fell at free fall. (NIST says so in writing.)
Expressing this using vector calculus, it is complex, but expressing this using energy, it is simple, as follows.
Note that this analysis is so simple because (1) energy is conserved and (2) free falling is the asymptotic edge case of ways structures can fall. At the asymptote there is no wiggle room, so additional confounding complexities simply go away.
Doing any work requires energy. (1) Accelerating the building downward is work. (2) Deforming a building is work.
Falling is the conversion of potential energy into kinetic energy. The falling is free falling when the efficiency of this conversion is 100%.
Therefore, if the only energy available is the potential energy of the mass suspended at height in a force field, then when free falling there is NO additional energy to do ANY other work.
That is, when free falling, you spend ALL of the energy accelerating the mass downward; in particular, no energy remains to do the work of deforming the building.
You could say that the building fell, and then stopping falling deformed the building, but then time goes in the wrong order: you have to deform the building so that it will fall.
At the first press conference NIST gave after 9/11, someone yelled out to the head of NIST "WTC7 fell at free fall". The head of NIST responded like he was reciting something he learned long ago: "no, it can't have, because you cannot have a progressive collapse of a structure at free fall". (Above I just gave the conservation of energy proof of this statement.) (Link wanted for this interaction).
I think it was six months later that NIST published that WTC7 fell "at free fall for several seconds". It cannot fall at free fall for any number of seconds. (Link wanted for this document).
What got me into this was seeing a YouTube video of a high-school physics teacher plotting each frame of the building falling and getting -10 m/s^2, which is free fall plus a bit of fudge factor. (Link wanted for this video.)