fobos ha scritto:
Citazione:

Tutte cose che non sai evidentemente calcolare nemmeno approssimativaente. E poi, che coraggio a tirare ancora fuori la storia della caduta libera!! (oppure che poca voglia di leggere gli altri 3d)

Proprio un bel coraggio con questa storia della caduta libera!!! Hai detto bene,....infatti è una contestazione che proviene dal versante complottistico, ma è risaputo che da tempo fra di voi non andate molto daccordo!!!!
Puoi sfalsare tutti i calcoli che vuoi, ma le immagini documentano la caduta libera di alcuni pezzi (alcuni di dimensioni molto grandi), che precedono il fronte del crollo, che avviene invece, a differenza della demolizione controllata, in caduta frenata dalla resistenza della struttura delle torri. La differenza che si vede nelle immagini è chiarissima. Alcuni detriti incontrano solo la resistenza dell'aria (caduta libera) e tutto il resto segue più lentamente.
La caduta libera non è pertanto una caratteristica di questo evento.

6. How could the WTC towers collapse in only 11 seconds (WTC 1) and 9 seconds (WTC 2)—speeds that approximate that of a ball dropped from similar height in a vacuum (with no air resistance)?

NIST estimated the elapsed times for the first exterior panels to strike the ground after the collapse initiated in each of the towers to be approximately 11 seconds for WTC 1 and approximately 9 seconds for WTC 2. These elapsed times were based on: (1) precise timing of the initiation of collapse from video evidence, and (2) ground motion (seismic) signals recorded at Palisades, N.Y., that also were precisely time-calibrated for wave transmission times from lower Manhattan (see NCSTAR 1-5A).

As documented in Section 6.14.4 of NIST NCSTAR 1, these collapse times show that:

“… the structure below the level of collapse initiation offered minimal resistance to the falling building mass at and above the impact zone. The potential energy released by the downward movement of the large building mass far exceeded the capacity of the intact structure below to absorb that energy through energy of deformation.

Since the stories below the level of collapse initiation provided little resistance to the tremendous energy released by the falling building mass, the building section above came down essentially in free fall, as seen in videos. As the stories below sequentially failed, the falling mass increased, further increasing the demand on the floors below, which were unable to arrest the moving mass.”

In other words, the momentum (which equals mass times velocity) of the 12 to 28 stories (WTC 1 and WTC 2, respectively) falling on the supporting structure below (which was designed to support only the static weight of the floors above and not any dynamic effects due to the downward momentum) so greatly exceeded the strength capacity of the structure below that it (the structure below) was unable to stop or even to slow the falling mass. The downward momentum felt by each successive lower floor was even larger due to the increasing mass.

From video evidence, significant portions of the cores of both buildings (roughly 60 stories of WTC 1 and 40 stories of WTC 2) are known to have stood 15 to 25 seconds after collapse initiation before they, too, began to collapse. Neither the duration of the seismic records nor video evidence (due to obstruction of view caused by debris clouds) are reliable indicators of the total time it took for each building to collapse completely.