I would like to commemorate the twelfth anniversary of 9/11 with a simple physics lesson using the collapse of the south tower (WTC 2) for our example. The equations for a falling body are below.

distance = (1/2) * gravity * time(squared)

velocity = gravity * time

gravity = 9.81 metres per second squared

If we were in a vacuum at a height of 415 m and dropped a bullet it would hit the ground in 9.2 seconds by the first equation, and reach a speed of 90.24 m/s or 324.8 km/h by the second equation. Now let's say we are standing on the roof of the south tower at a height of 415 m, there is no wind, and we drop our bullet over the edge. Will it still hit the ground in 9.2 sec? No, because we have now introduced air resistance into our problem which means our bullet will experience drag and eventually reach a terminal velocity. However, the terminal velocity for a bullet is around 320 km/h which is close to our vacuum speed of 324.8 km/h at impact so we can perhaps estimate an additional 0.5 seconds would be required for our bullet to hit the ground or 9.7 seconds.

In chapter 9 of the official 9/11 commission report it states:

At 9:58:59, the South Tower collapsed in ten seconds, killing all civilians and emergency personnel inside, as well a number of individuals-both first responders and civilians-in the concourse, in the Marriott, and on neighboring streets. The building collapsed into itself, causing a ferocious windstorm and creating a massive debris cloud. The Marriott hotel suffered significant damage as a result of the collapse of the South Tower.

According to this report, the south tower collapsed in ten seconds and from our previous calculations, that is essentially the same amount of time as it took our bullet to reach the ground when dropped from the roof of the south tower. So how is it possible that the roof of the south tower could reach the ground in the same amount of time as our bullet when there were 110 floors of building below it and not just air?

There is a well understood technique known as a "controlled demolition" or "building implosion" that would make this possible.

...the technique weakens or removes critical supports so that the building can no longer withstand the force of gravity and falls under its own weight.

Numerous small explosives, strategically placed within the structure, are used to catalyze the collapse. Nitroglycerin, dynamite, or other explosives are used to shatter reinforced concrete supports. Linear shaped charges are used to sever steel supports. These explosives are progressively detonated on supports throughout the structure.

So a possible theory for the collapse of the south tower is that explosives allowed the roof to collapse, but before the roof hit the top floor, explosives caused that floor to collapse, then before that floor hit the next, explosives caused it to collapse. This would need to continue in rapid succession such that every floor is falling through air and experiences nothing more than air resistance all the way down.

Of course, the official explanation for the collapse doesn't involve explosives and has been summarized at Wikipedia as follows:

Once the collapse initiated, the mass of failing floors overwhelmed the floors below, causing a progressive series of floor failures which accelerated as the sequence progressed.

According to this explanation, each floor did provide resistance to the collapse. So it should be obvious that something doesn't add up. How could 110 floors of steel and concrete resistance produce the same result as only air resistance? The answer is it can't.

The video below has been produced by Architects and Engineers for 9/11 Truth. It provides all of the evidence that supports the theory that the WTC towers were brought down by explosives in a controlled demolition. At the 1:16:00 point is a clip of the 10 sec collapse of the south tower that I explained here.

If this is your first time at my blog and are interested to know who I feel is actually responsible for 9/11, then I highly recommend you view the movie Thrive.