Upper Part of WTC 7 drops free fall for 2.25 Seconds
Anders Bjorkman discusses WTC7 collapse on his website at: heiwaco.tripod.com/nist7.htm
NIST has agreed/confirmed the finding that the upper part of WTC 7 free fall drops (acceleration 9.82 m/s²) for 2.25 seconds during the collapse, i.e. there is no support/resistance of the upper part above floor 16, when it displaces downward abt 32 meters. See e.g. figure 3.15 in the report (also below)
According NIST the constant acceleration of the roofline is 32.196 feet/s² or 9.814 m/s² between time 1.75 and 4 seconds when the roofline velocity increases from 11.57 to 84.01 feet/s or 3.52 to 25.61 m/s! This acceleration is equivalent to gravity acceleration = 100% free fall drop. The average speed during this time is 14.56 m/s and the total free fall displacement is 32.77 meters. This makes controlled demolition the OFFICIAL position of NIST.
Anyone who does not understand this, simply does not understand what free fall drop means. Free fall drop means NOT DOING ANY WORK INCLUDING DESTROYING STRUCTURE BELOW AT ALL - OTHER THAN FALLING.
It evidently means that 32.77 meters height of structure below must have been destroyed completely for the roofline to free fall drop.
NIST has agreed there was freefall for 2.25 seconds. This implies 32.77 meters of the fall was without any obstruction from below. So therefore all column supports in at least eight floors must have been removed instantaneously, or at most within under 2.25 seconds. Thats 24 interior columns and 26 perimeter columns - 50 columns on 8 floors destroyed in under 2.25 seconds. Is this possible without additional explosive force, ie controlled demolition?