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29th October 2006, 11:37 AM | #281 |
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Glad to. Thank you for entering an actual discussion. This way, we can both learn something.
Air resistance adds very little to that. As I have noted here dozens of times, the tower is not falling in a free-stream of still air. The only air drag on falling objects is on the sides. Even if it was, air drag creates a drag force proportional to the square of the falling object's velocity. Because this is a non-linear relationship, the drag will be a minor correction until the velocity becomes reasonably close to the terminal velocity of the object falling. A steel girder will have a terminal velocity in excess of 110 meters per second. Free-fall in vacuum for 9.2 seconds only gets you to 90 meters per second. So even at worst, air drag is minor. But remember that we are concerned with an object that falls on itself and accelerates, not one that falls at "free-fall" speeds. If we assume the top of the tower hits ground in 15 seconds, and accelerates at a constant rate, then its speed at impact is only 56 meters per second. Again, even if it fell in a free stream of air which it didn't, this means the drag force is at most only a quarter that of gravity. And remember, this is for the very top which moves the fastest. The overwhelming majority of the tower never gets to those speeds. When we also take into account the fact that it didn't fall in a free-stream, we may safely neglect drag entirely. No, I don't. You see, the fact that it slows down 33% means that 1 - (0.66)2 = 54% is left for deformation. Likewise, slowing to 12 seconds (a 25% slow down), not supported by the video but let's do it anyway, leaves 1 - (0.75)2 = 43% available for deformation. Plenty. Think of it this way. How long does it take you to stop your car when you're driving 50 kph? Now try it from 100 kph. Is the stopping distance the same, or longer? Why is this? (It's because energy scales with the square of velocity.) Wood is severely out of her depth. The "lost" energy is all going towards deformation. Where else can it go? |
29th October 2006, 11:54 AM | #282 |
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29th October 2006, 01:49 PM | #283 |
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forgiddaboudit, RM
These guys are convinced that velocity in air of a steel bar= velocity in air of pulverized concrete=velocity in air of a feather. After all, didn't Gallelio prove.... sigh.
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you can't use that liitle ^2 there, can you? it is obvious via common sense that a semi and a motorcycle will stop in the same distance from the same speed, idn't it?
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sigh... To paraphrase Robert A. Heinlein --an individual who cannot deal with math is a best a sub-human beast who might possibly be trusted to learn not to soil himself... |
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29th October 2006, 02:09 PM | #284 |
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Mackey -
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Next we have to subtract the percentage of mass which landed outside the footprint. As mentioned, the "dust" which "puffed" out of the towers in all directions was very dense, falling nearly as rapidly as steel. Could we not estimate the density of this "dust" from its fall time? Could we not estimate its volume in comparison to the intact tower? Considering density and volume, could we not estimate the mass which landed outside the footprint? |
29th October 2006, 02:26 PM | #285 |
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Fair enough, except your numbers imply a collapse time from the top of 11.5 seconds. I'm not sure that number is supported by the video.
Another thing to consider is that we're consider comparison vs. "free fall" from the top of the structure, not the middle where it was hit. And given the huge clouds of dust and smoke, it's quite difficult to estimate when the timer should be stopped. My only point with this argument is to show that "near free fall" is a specious argument. Slowing down the collapse even by two or three seconds means that an enormous release of energy took place as it fell -- 35% to over 50% of the total collapse energy. Thus, any argument based on it happening "too fast" is bunk. Much of that dust is going to be fine drywall, relatively light. Also the size of the cloud does not indicate how dense the cloud is. Given that the dust is opaque, I don't think you can make a valid estimate -- there are just too many variables. Furthermore, we similarly have a hard time estimating just how much damage was caused during the collapse versus after the pieces hit the ground. We just don't have enough visibility into the collapse. Regardless, as my simple math shows, the amount of energy expended during collapse is huge -- greater than 3 x 1011 Joules per tower -- and thus the phenomenon seen is entirely credible. Likewise, if this isn't enough energy, then you need to find an absolutely enormous source of energy other than gravity, and one that leaves no telltale signatures. Explosives would have been heard, shattered windows, killed people standing nearby and been so large as to have been utterly impractical in the first place. I can't think of any other candidates. |
29th October 2006, 06:07 PM | #286 |
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Correct, I believe, and I think analyzing the collapse time vs. free-fall time in terms of "lost" energy is not the proper analysis. The thing that would slow the collapse is the transfer of momentum from the falling section to the next impacted floor (and somewhat to floors below that, through the columns): Since the original mass is increased by the mass of the impacted floor, the velocity must decrease in accordance with the momentum conservation law. But from the videos, that appears to be exactly what's happening in the early stages of the collapse, since it's clear that the debris falling outside the building is falling faster than the collapse is proceeding. What happens, though, is that more and more mass gets to moving faster and faster as the collapse proceeds, until the momentum that's being transferred is too small a percentage of the total momentum to slow the falling mass by any significant percentage -- "near" free-fall.
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29th October 2006, 08:37 PM | #287 |
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I was using 15 second collapse time, and 12 seconds as free fall time with air resistance.
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Explosives heard? Plenty of them were heard at various times. The lack of a definitive "crack" at the beginning of the "collapse" may well be explained by high energy weapons, as suggested by Wood and Reynolds. In fact, as I think about it, the star wars beam solution answers a number of questions. |
29th October 2006, 08:43 PM | #288 |
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the beam weapon is pure nuts, with no proof these two people are just plain nuts.
I did not say beam weapons do not exist, in I think there has been a test of an air borne laser weapon But the gravity collapse of the WTC has plenty of energy, you only have to ask an engineer (me) or a CD expert. You will have to find the CD guy since you do not trust me as a EE. They debunk Dr Jones, Morgan believes no planes hit anything. So you hitch your wagon to two idiots, one with no planes, the other who messes up basic momentum using balls. |
29th October 2006, 08:46 PM | #289 |
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Nope. Your figure was 80%, meaning the collapse was slowed by 20% from its theoretical maximum of 9.2 seconds, which works back to exactly 11.5 seconds.
You can't compute free-fall time with air resistance without making more specific and very important assumptions. Yes, there was quite a lot of dust created. Changes nothing... anything turned to dust has already participated in the crumbling, and has expended its energy. There is no significant loss. I didn't realize you were a mindreader as well! Please, elucidate. I did acknowledge it. I also said it was foolish. I do not believe you can make a reasonable mass estimate of the cloud. We have dust samples and debris studies, but they were taken much later. We do not have a real-time estimate of the cloud composition, size, or density. Feel free to prove otherwise if you know of someone who thinks differently. You'll have to prove that. But that's not the point. All windows within a klick or so would have been blown out, if an explosive releasing over 3 x 1011 Joules was employed. Believe me, we'd know. Beam weapons are fantasy. The only thing even close to deployment is the Boeing ABL (AirBorne Laser), which is a measly megawatt class weapon. It would require over 80 hours of continuous firing to generate the kinds of energies seen here. Really, if you're going to retreat to your comic books, there's little point in this discussion. |
29th October 2006, 08:50 PM | #290 |
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Yes. Mainly it answers the question, "How can we tell a 9/11 crackpot from a garden-variety 9/11 denier."
TS, you never explained how you reconcile this statement
Originally Posted by TruthSeeker1234
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29th October 2006, 08:55 PM | #291 |
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Hint: If you need imaginary technology to answer the questions, your answers are raising more questions than they are answering.
Of course, the reason that conspiracy hucksters like Wood and Reynolds are pushing imaginary technology like beam weapons and mini fusion bombs is that the traditional explosives and/or thermite hypothesis just won't withstand scrutiny. Those "answers" are absurd, but nobody can prove they don't exist. |
29th October 2006, 10:15 PM | #292 |
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Let's see. Multiplying 200 ft x 200 ft x 1300 ft i get 52,000,000 cu ft for the total volume of a tower. If the tower is 90% air, this is 5,200,000 cu ft of solid stuff.
During the "collapse", the dust outside the tower looks to be at least as big as the tower. So the volume of the dust is 52,000,000 cu ft. If the dust is 10 percent as dense as steel, this means all of the mass was converted to dust. We see some steel left over at the end, so this can't be right. Especially considering that the "dust" fell almost as fast as the steel, indicating that it is very dense. Perhaps the dust was only half the size of the whole tower, although it sure looks bigger. If the dust is half the size of the tower, and is has a density 16% that of steel, that would mean that 80% of the mass of the tower was converted to dust. I think that matches our observations fairly well, that is, it looks like around 20% of the mass of the towers survived, mostly steel and aluminum. |
29th October 2006, 10:32 PM | #293 |
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29th October 2006, 10:33 PM | #294 |
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OK. 1.67 million cubic meters is the more accurate figure. Using your 90% hypothesis, that also gives you an average density of 3000 kg / m3 or 182 pounds per cubic foot of the solid stuff. Feels a tad high but pretty reasonable.
Problems here. I don't know how to eyeball the dust cloud. Saying it's comparable to the size of the intact tower is fair, but there's potential for at least a full order of magnitude of error here. The dust on the ground is probably the same mass as the tower, or perhaps lighter, since it's made of the same stuff. The dust in air is going to be very hard to estimate. I don't buy that the dust suspended in air is 10% as dense as steel, though. That would mean a dust density of 780 kg per cubic meter (assuming 10% of the density of A36 structural steel), which means each kilogram of air (density of air is about 1.27 kg / m3) would have to suspend 603 times its own weight in dust. Not likely. I suggest you're definitely off by at least two full orders of magnitude, and probably three. If I assume the dust cloud is the size of the tower, and use a more credible (but still high) estimate of 600 grams of dust for every kilogram of air in the cloud, that gives me almost exactly 1 million kilograms of dust. That's a mere 0.2% of the tower's mass. No, it doesn't. I also question, as I have from the first day you arrived here, the source of your "observation." I believe much, much more than 20% of the mass of the towers fell to the ground. By the estimate above, I would say more than 99% survived. |
29th October 2006, 10:33 PM | #295 |
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29th October 2006, 11:09 PM | #296 |
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30th October 2006, 05:07 AM | #297 |
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And I think you've made your estimates with the answer you wanted to find in mind. From this paper at Implosion World, they state (see page 5, discussion of Assertion #3) that typical human-inhabited buildings are about 30% structural elements and contents, so your 10% value is off by about a factor of 3. Other people have discussed the density of the dust in the air. There are so many possible variables on this that there's no way, short of some serious reasearch in a lab perhaps, of getting a realistic estimate of this value. So once again, you're free to pull out any number you want to get the answer you're looking for. So your calculation is basically worthless. |
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30th October 2006, 07:25 AM | #298 |
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30th October 2006, 07:35 AM | #299 |
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30th October 2006, 07:42 AM | #300 |
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Hey - BS1234 said something that's correct!
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30th October 2006, 09:10 AM | #301 |
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30th October 2006, 09:18 AM | #302 |
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This thread has all the makings of an instant-headache generator.
Estimating turbulent heterogenous gas/solid mixtures acting as a liquid, and doing crude calculations like this... is a recipe for fun. For a guy who doesn't really have a handle on Newton's three laws, I'm thinking this can't turn out well, Truthseeker. |
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30th October 2006, 09:24 AM | #303 |
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If the dust isn't significantly dense, then why does it fall so fast? I observe large quantities of dust that falls almost as rapidly as does steel. I repeat my challenge. Can we not get a handle on the density of the dust via its fall time? Fall time in air is directly indicative of surface area-to-mass ratio.
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30th October 2006, 09:26 AM | #304 |
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30th October 2006, 09:30 AM | #305 |
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30th October 2006, 09:30 AM | #306 | |||
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Didn't Galileo cover this awhile ago?
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30th October 2006, 09:33 AM | #307 |
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30th October 2006, 09:35 AM | #308 |
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30th October 2006, 09:35 AM | #309 |
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30th October 2006, 09:36 AM | #310 |
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30th October 2006, 09:36 AM | #311 |
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Yes, you can calculate the terminal velocity of a small object (e.g. dust particle) using Stokes' Theorem.
If your "dust" fell "almost as fast as steel," then the dust should all be lying on the ground after about 15 seconds, right? Strange definition of dust you're using. Anyway, my estimate, using air that contained 60% dust by mass, is quite high, and even I don't believe it. You postulated dust that was denser than rolls of chainlink fence, or comparable to solid oak. This is not "dust," TruthSeeker1234. But thank you for adding some detail. This makes is much easier to determine where the fault in your reasoning process lies. Now all we have to do is get you to understand it, and we've made real progress. |
30th October 2006, 09:39 AM | #312 |
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30th October 2006, 09:40 AM | #313 |
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I was a little bit working on some calculations, last time I used that antenna of wtc1 to check the time it took to fall a distance of 3.8 meter.
It it is about 1.3 seconds. The story is that the block falls as a whole and then the collision on the next floor will domino the next floor and so on, I used that antenna because its very good visible in the beginning and no smoke and dust covers it. The strange thing is that if you look at the rest of the block you see absolutely no movement (virtualdub can be used for a frame per frame analysis). It almost looks like a kind of penthouse failure that wtc7 also has. That same movie also shows that about 10 seconds before the initial moment of movement of the antenna some debris falls away from the impacted floors, the camera that was fixed somewhere else also started shaking. There is no sound in the movie. I'm wondering if that fits with the thunder sounds in 911eyewitness, anyone noticed this ? |
30th October 2006, 09:41 AM | #314 |
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30th October 2006, 09:41 AM | #315 |
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Have you accounted for air currents and subtracted them out, yet? Air resistance is calculated with a velocity relative to the air, not the ground. If the air is moving downwards, then the dust will 'go with it' with no resistance.
Have you estimated the airflow and subtracted it out, yet? ETA: Btw, you get +40 points on the crackpot index (http://math.ucr.edu/home/baez/crackpot.html) for comparing yourself to Galileo 40 points for comparing yourself to Galileo, suggesting that a modern-day Inquisition is hard at work on your case, and so on. |
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30th October 2006, 09:48 AM | #316 |
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That is why we started a free society. So real scientist would not be jailed by fools like those in the truth movement when real scientist publish the truth; the real story. I am sure the truth movement leaders would jail anyone, if the truth movement was in charge, who did not agree with their CT world.
But the truth movement is not in jail because we have a free society, and we like to have nut cases display their ideas in the open so we can spend more or less money on education. We have decide to "pull it"; all future funding of your education. Further expenditures are futile in your case of the never ending CT story. |
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30th October 2006, 09:59 AM | #317 |
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I have no doubt of that. Imagine a world where people can be accused of the worst possible crimes on hearsay, conjecture, and rumor.
Like many revolutions, the "hang 'em high!" crowd's cure will be worse than the sickness. Sort of like replacing the corrupt Tsars of Russia with what would become in a few short years the nightmare of Stalin. I wonder if the scientists who support the 'old order' will be the first to go. |
30th October 2006, 10:04 AM | #318 |
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30th October 2006, 10:15 AM | #319 |
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I think that TS1234 means:
- the collapse is of course less than an object in vacuum or air as we see because the debris is falling faster than the demolition wave - this means that the debris that falls has a high terminal velocity, i.e. it is no dust that hangs in the air and is dense mass. is that true TS1234? |
30th October 2006, 11:08 AM | #320 |
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Relative to what? Terminal velocity is relative to the air, not the ground. I'm still awaiting his calculations to determine how the frame of reference defined by the air converts to the frame of reference of the ground. In other words, I'm still waiting to see his calculations for the movement of the air.
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