World Trade Center 7 collapsed in under 7 seconds and achieved free fall for 2.25 seconds as admitted by NIST. 2.25 seconds times the standard gravity (9.81 m/s) gives us about 22 meters. Convert that to feet and it is 72'. Free fall occurred for 72 feet or roughly 7 stories.
Look around your neighborhood and try to envision a 7 story building.
Now take your keys and drop them from shoulder height. That is how fast that building came down.
Literally turning into dust for 81 columns on 7 floors SIMULTANEOUSLY (keyword). They were all severed at exactly the same time.
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glugglug ago
The 9.8 m/s is acceleration, not velocity. So your math is wrong, depending on which 2.25 seconds are in question. That said, the minimum free fall distance is the 2.25 seconds of free fall was the first 2.25 seconds of collapse starting from rest is even bigger than you just calculated, instead at least 80 feet minimum that NIST has admitted to.
WTC_7 ago
Correct sir. I'm not sure if this building reached "terminal velocity", but that is what my calc would be based on. Basically, as you said, my value is the minimum.