# Why the WTC towers fell at almost free-fall speed

By Dave Burton via Burton Systems Software – (burtonsys.com)

Some conspiracy theorists are puzzled about why the WTC towers fell at almost free-fall speed on Sept. 11, 2001. They suppose that the speed of collapse is evidence that something or someone must have destroyed the structural integrity of the undamaged lower part of each tower.

After all, they reason, “only the upper floors of the building were damaged, so why did the lower floors collapse, and why did they fall so fast?”

This web page answers those questions, simply enough for even a conspiracy theorist to comprehend (I hope). I do use some simple math and some very basic physics, but even if you don’t understand that part you should still be able to comprehend the basic reasons that the towers fell so fast.

What the conspiracy theorists apparently don’t understand is the difference between static and dynamic loading. (“Static” means “while at rest,” “dynamic” means “while moving.”)

If you don’t think it can make a difference, consider the effect of a stationary bullet resting on your chest, compared to the effect of a moving bullet striking your chest. The stationary bullet exerts a static load on your chest. A moving bullet exerts a dynamic load.

As a more pertinent example, consider a 110 story building with a roof 1,368 feet high (like the WTC Twin Towers). Each floor is 1368/110 = 12.44 feet high, or aproximately 3.8 meters.

Now, suppose that the structural steel on the 80th floor collapses. (Note: I’m using as an example 2 WTC, which was the building that collapsed first.)

The collapse of the 80th floor drops all the floors above (which, together, are equivalent to a 30 story building!) onto the 79th floor, from a height of aproximately 12 feet.

Of course, the structure of the lower 79 floors has been holding up the weight of the top 31 floors for many years. (That’s the static load.) So should you expect it to be able to hold that same weight, dropped on it from a height of 12 feet (the dynamic load)?

Here’s why.

MORE . . .