Thread: Common Sense
View Single Post
Old 7th January 2007, 05:53 PM   #631
R.Mackey
Philosopher
 
R.Mackey's Avatar
 
Join Date: Apr 2006
Location: The armpit of L.A.
Posts: 7,857
Originally Posted by 28th Kingdom View Post
Okay...let's break down what you said... firstly, near freefall isn't a scientific term... agreed. And, then you claim that 15 seconds compared to 9.2 seconds is NOT near freefall speeds. So, who endowed you with this judgment? So, scientifically speaking... what time would be near 9.2 seconds. 10 seconds? 11 seconds? 12 seconds? What definition of "near" are you working with?

You understand if the towers had fallen in 9.2 seconds... it means a synthetic catalyst had to of been used, right? So you add 4-6 seconds to this... factor in probability and common logic... and what do you get?
Since you still refuse to address my post, like you promised, I surmise I've made your vaunted "Ignore" list. But in case not, let me explain your fallacy here.

9.2 seconds is totally different from what you get if you "add 4-6 seconds." A simple calculation will confirm this.

Suppose we compute the time it takes the roof to hit the ground. Let the acceleration be a, in which case the time it takes to hit can be found using d = 1/2 a t2, where d is the distance the roof has to fall, equal to about 417 meters, and t is the time of the fall. We know d, measure t, and work backwards to get the effective acceleration a.

If the structure absorbs no energy at all, i.e. we get freefall, we should measure a = g. In this case, we should see t = 9.2 seconds.

If the structure absorbs some energy, then a will be less than g, or better expressed as a fraction of g.

Once we have this fraction, we can then estimate how much energy was needed to destroy the structure as it fell. Recall that gravitational energy GPE = m g h, where m is the mass of the structure. But this is the same g. Since the building doesn't collapse with acceleration g, the percentage of the GPE that at any time is seen as kinetic energy is not used to destroy the structure, and the remainder must have been needed to destroy the structure.

In other words, the fraction 1 - (a / g) is equal to the fraction of energy that went into destroying the structure.

From calculations elsewhere, the total GPE of the structure was equal to roughly 160 tons of TNT equivalent.

I've made a table for you that describes, for certain values of collapse time, how much energy went into destroying the structure as it fell:

Collapse time ............... Structural fraction ............. Structural energy
---------------------------------------------------------------------

9.2 seconds ................. 0 ................................... 0
10 seconds .................. 0.15 ............................... 24 tons TNT
11 seconds .................. 0.30 ............................... 48 tons TNT
12 seconds .................. 0.41 ............................... 65.6 tons TNT
13 seconds .................. 0.50 ............................... 80 tons TNT
14 seconds .................. 0.57 ............................... 91.2 tons TNT
15 seconds .................. 0.62 ............................... 99.1 tons TNT

What does this mean?

It means, that "adding 4-6 seconds," far from being materially identical to free-fall, means that as much as 62% of the energy was dedicated to breaking the building.

Even a single second of resistance by the structure means it absorbed more energy than an entire truckload of pure high explosive -- far, far more than could possibly have been planted, under any scenario.

Once again, your "common sense" as you call it, is wrong. And feel free to show where I'm "throwing my hands in the air" and disobeying the laws of physics.
__________________
"Nothing real can defeat us. Nothing unreal exists." -B. Banzai

VT VENIANT OMNES

Last edited by R.Mackey; 7th January 2007 at 05:57 PM. Reason: Myriad formatting issues... don't mind my OCD.
R.Mackey is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top