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Dave W.
Info Junkie
USA
26021 Posts |
 Posted - 03/18/2009 : 18:42:23 [Permalink]
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Originally posted by Atheria
I can't emphasize too much how important it is that you consider especially the toughest objections to your beliefs.
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So I should continue to debate b/c that's what's best for me? Wow! Never knew ppl could care so much, other than my family.
Seriously folks... what do I respond to that with? |
You either take it as it was intended, or you don't. [shrug]
I'm sure I can speak for most people here when I say that we think that cutting off discussion on a subject is the opposite of our goals here, no matter how aggravated the discussion makes you or us. Especially if your goal is to honestly and openly test your ideas against other peoples' ideas. The venue (real life or the Internet) would make little difference, if such were the case.
If, on the other hand, your only goal here was to convince us of the truth as you know it, and to brazenly insult us when you fail, I will warn you that you'll get back what you dish out, and then some. I've already pointed out where you fired the first shots in the "war" that you're trying to blame on us, so at the very least, quit trying to portray yourself as an innocent victim. 
[sniff] I guess the love is gone already. |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too. |
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Dr. Mabuse
Septic Fiend
Sweden
9687 Posts |
Posted - 03/23/2009 : 14:04:12 [Permalink]
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Originally posted by Atheria
1. The towers fell too quickly to be a pancake collapse.
<snip>
I will now ask what you think a reasonable time for the breaking of the bounds of the steel structures underneath each floor would be. |
Micro-seconds.
The key word is impulse.
After the fist floor collapsed, it started falling down onto the next floor. The momentum of the floor comes from the potential energy of 2.5 meters (that's my guess about the floor heigt, I haven't consulted the technical specification but this is not to make so much exact calculations as establishing the physical principles in action) it has to fall before hitting the underlying floor.
Since the floors are secured with steel, there's not much flexibility in the structure. The steel bolt's length varies a fraction of a percent in lengt as pulling force increase the stress in it. This allows for a few cm of sagging in the middle of the floor before reaching breaking point.
But the horisontal force create a shearing stress on bolt at the outer wall. If the bolt is 10cm in diameter, the elasticity in the bolt will not allow for more than perhaps a few hundred micrometer flexing before reaching critical shearing stress that result in breaking. If we assume that the bolt can flex 0.8mm, the steel bar in the outer wall another 0.8mm and the steel structure in the wall 0.8mm, you'll have a total stress felxibility of ~2.5mm
You have a floor that has at about 2.5mm of distance to slow down the upper falling floor to a stop in order not to break. The falling floor has 2.5m of free fall acceleration, and if the underlying floor is to stop it, it has to exert a force 1000 times that amount in order to break its fall. But it was not made to withstand such a force. A reasonable (again, I haven't consulted the technical specification) construction should be able to carry twice its weight, which amounts to three times the weight of the floor.
The maximum force that can break the fall of the first floor is less than a third of a percent of what is necessary to entirely break the fall. In fact, because of the high impulse generated at impact, braking the second floor support provides negligible slowing of the fall.
At this point of impact, the falling floor will transfer half of its falling momentum to the resting second floor that hasn't had time to start falling. This result in the two floors having half the velosity of the falling floor had at the moment before the impact.
This will slow down the progress of the collaps somewhat. But consider... the next impact the falling velosity will only be reduced by a third because we have the momentum of two moving floors that has to share their momentum with the third one. For each floor, the loss of momentum in the fall will only be a fraction of the previous one.
If anyone see a flaws in my reasoning please point them out so we can discuss them.
In fact, I know already there is at least one flaw. Let's see who spots it. The error is in favour of a slower falling tower. |
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Guantanamo detainees say they planned Sept. 11
