WTC7 and the other 2 towers were brought down with explosives in 6.5 seconds & 10.5 second, thats how much time it will take  an object to hit to the floor if dropped from top of those buildings, Collosal 47+47+24 Main Steel Support Columns  did not resist the fall at all, because they were taken out w/explosives mili-seconds ahead of the fall.