20 9/11 Questions Remain Unanswered over 8 Years Later, page 6

Originally posted by jthomas
We already know that the internal collapse within WTC 7 started 6+ seconds before the facade began to collapse. We also know that there was a 2.25 second free fall period in the middle of the facade collapse, preceded and followed by slower than free fall speeds.

jthomas is trying to twist, dodge, deflect and avoid the fact that for a period of 2.25 seconds, WTC 7 fell with free fall acceleration.

He also needs to brush up on his basic physics, as there was a free fall acceleration between 1.75 s and 4.0 s - not a free fall speed.

Here's part of the NIST final report on WTC 7:

The timing of global collapse of WTC 7, as indicated by downward motion of the north exterior face, was investigated using a video of the collapse taken from the vantage point of West Street near Harrison Street. An initial analysis compared the observed time it took for the roofline to fall approximately 18 stories to the free fall time under the force of gravity.

A more detailed examination of the same video led to a better understanding of the vertical motion of the building in the first several seconds of descent. NIST tracked the downward displacement of a point near the centre of the roofline, fitting the data using a smooth function. (The time at which the motion of the roofline was first perceived was taken as zero.) The fitted displacement function was then differentiated to estimate the downward velocity as a function of time, shown as a solid curve in Figure 3-15.

The slope of the velocity curve is approximately constant between about 1.75 s and 4.0 s, and a good straight line fit to the points in this range (open circles in Figure 3-15) allowed estimation of a constant downward acceleration during this time interval. This acceleration was 32.2 ft/s^2 (9.81 m/s^2), equivalent to the acceleration of gravity g.

For discussion purposes, three stages were defined, as denoted in Figure 3-15:

• In Stage 1, the decent was slow and the acceleration was less than that of gravity. This stage corresponds to the initial buckling of the exterior columns in the lower stories of the north face. By 1.75 s, the north face had descended approximately 2.2 m (7 ft).

• In Stage 2, the north face descended at gravitational acceleration, as the buckled columns provided negligible support to the upper portion of the north face. The free fall drop continued for approximately 8 stories or 32.0 m (105 ft), the distance travelled between times t = 1.75 s and t = 4.0 s.

• In Stage 3, the acceleration decreased somewhat as the upper portion of the north face encountered increased resistance from the collapsed structure and the debris pile below. Between 4.0 s and 5.4 s, the north face corner fell an additional 39.6 m (130 ft).

1.75 s after the building began to fall, it experienced free fall acceleration for a further 2.25 seconds.

How does a building fall for 2.25 seconds without any resistance being applied by the structure?

NIST does not answer this question!!!
jthomas does not answer this question!!!

Originally posted by jthomas
There is nothing suspicious here, as Truthers want us to believe there is.

There is definitely something suspicious here and jthomas is trying to deflect your attention away from it.

His lack of basic physics, his attempted distortion of the building's collapse time (taken to be zero, when the roofline was first observed to move) and his inability to answer why the building fell at g for 2.25 seconds, all indicate the manner in which an official government story believer will attempt to obfuscate the truth.