The 9/11 Forum

David B. Benson wrote:

femr2 wrote:... extrapolating a descent time ...

Please do so.

Video #1 trace:

With rudimentary scaling, ~27m/s for some of the latter portion.

And it would *appear* to be slowing down.

Using the higher detail BBC footage...

Decidedly higher maximum velocity.

Assuming 27m/s continues, we'd have, what...

186m of WTC 7 left to go unil GZ, at ~7.5s after initiation.

7.5+6.8=14.3s

VERY rough calc, which I'll improve upon considerably once I get the BBC footage done properly, but a number to throw around for a bit.

David B. Benson wrote:femr2 --- Of course GZ is not crush-down-complete because there are still all the basement levels to traverse. But by several different analyses by different people, numbers in the 14--15 second range are found. Nothing outside that.

"Collapse Time" has never been a metric to describe the mathematical notion of "Crush Down Completion", but, as I say, I'll refine the timing with additional data as-and-when.

I define "Collapse Time" to be the time in which destruction of the building reaches ground level.

Edit: I define one form of "Collapse Time", though the most common conception, to be the time in which destruction of the building reaches ground level. Given the thread title, ALL forms of the definition will hopefully be included here, including the additional time required for destruction to reach lower basement levels, and separately *crush down complete* timings, which will obviously be different to the time at which the lowest portion of the lowest *crush front* reaches GZ/Basement.