9/11 Collapse Theory Discussion III

Fidel wrote:

....

It's not necessary in this case and with respect to Garcia's [url=http://www.counterpunch.org/physic11282006.html]The Physics of 9/11[/url] We See Conspiracies That Don't Exist. David Griscom, a retired research physcist for the US Navy, did not use calculus to calculate duration of impact based on Manuel Garcia's numbers. And there are at least two delta-t's in this particular physics problem of 3 metre fall and collapse initiation. There is an estimated time to impact as well the duration of impact.

The 'delta' simply means change or a difference of some measurable quantity and in this case, delta-t or a small difference of time in seconds. We were all introduced to the delta process in high school math when calculating slope of a line and graphing the result. m(slope)=(y-y2)/x-x2). y-y2 can also be written as delta-y. Similarly (x-x2) or simply delta-x . The slope of a line formula can be simplified to (delta) y / (delta) x.

Time to impact derives from s=Vot + gt^2/2 where s = the vertical height traversed = 300cm = 3m, Vo = the initial vertical speed = 0, t = the time to fall the 300cm distance and g = the acceleration due to gravity = 9.80m/sec^2 = 980cm/sec^2.

Therefore, 300cm = (0)t + 490t^2 from which t = sqrt(300/490) = 0. 0.782460 second(Garcia's time to impact)

0.782460 * 9.8m/s = 766.81cm/s = 7.7m/s(Garcia's instantaneous velocity of the upper block after a 3 metre fall)

Thank you for repeating some of the math I have already done.

Quote:

And with respect to Griscom's example for one degree of tilt for the upper block, we used trig to find a new delta-s or delta-y, or the height which the high end of the bottom floor of part C(Bazant) still has to fall after the lowest point of the upper block(part C) makes contact with part A(the lower block).

If s=vertical distance, then delta-s or ds= 111cm. dt=ds/v. 111cm/770cm/s = 0.144s. dt=0.144s(Griscom's delta-t)

This part is simply wrong. The math is correct, but is completely inapplicable to Garcia's criticisms. The duration of impact is, as you say, the amount of time it takes for the velocity to change.

You are assuming a constant velocity here. Garcia is assuming a changing velocity. Therefore your calculation for duration of impact is not the same as Garcia's.

Fidel wrote:

...

No I do not. Calculus can certainly be used, but plain old high school level math can suffice for the purpose of this discussion. Garcia's error is one of omission not a math error. Griscom and Garcia both generally agree that duration of initial impact was well below one second, and no amount of calculus is going to make up for the fact that Garcia failed to account for tilting of the upper block in his force balance equation. The photo at the bottom of this post shows how ridiculous it is to simply not mention it. Griscom's is actually a rough estimate for a new delta-t using basic trig and which is how I caculated dt for a one degree tilt as well. Griscom confirmed for me that this is how he arrives at dt=0.14s.

If that is how Griscom also arrived at 0.14 seconds, he is also wrong for incorrectly assuming a constant velocity.

Quote:

...

David Griscom is talking about a simple angular measurement effecting the duration of impact and changing the final value churned out of Garcia's force balance equation(time rate change of momentum). Slope of the 63.4m concrete slab is at one degree and producing an extra 1.11m of drop for the high end. This is very straight forward math. Failing to account for even one degree of tilt for the upper block is a significant error on Garcia's part when calculating total force. Using the calculus would not eliminate that kind of error of omission where, for example, a falling upper block is tilted by just one degree and leaving an extra 1.11 metres for the entire upper block to fall during impact. One degree was just an example. Video evidence shows the upper block tilting 23 degrees according to Griscom.

I will repeat this again: I never claimed that the upper blocks did not tilt. In fact, the tiliting disproves Ross's argument of stress transfer. The tilting may very well affect the duration of impact. I have yet to see any math that links the two.

Fidel wrote:

Photo showing obvious tilting of South Tower at or very near collapse initiation. Note deformation of lines at corners of the upper floors and undermining Bazant's theory for a "rigid upper block" even during start of collapse
[IMG]http://img.photobucket.com/albums/v697/rabblerabble/_1538563_thecollapse...

It is shortly after collpase initiation. You can tell because the debris cloud has started to be pushed out of the builidng envelope, but has not progressed very far.

I do not see this deformation of lines at corners.

I don't read every single post in every single thread of these discussions. I have seen video that challenges the notion that the collapse only took 13 seconds. These videos include a seconds counter with footage of the collapse.

Has 13 seconds to complete collapse been firmly agreed to by all parties at this point?

writer wrote:

...

Has 13 seconds to complete collapse been firmly agreed to by all parties at this point?

After asking jas and Fidel several times each about that very question, jas eventually confirmed that (s)he agreed with the collpase times that Greening calculated in his report.

(see page 16/32)

Fidel never answered the question.

Do you have a link to this video?

Haven't found it yet, but maybe this is of interest, Pants: http://www.youtube.com/watch?v=bMZ-nkYr46w

jas, do you remember the video I linked to a while ago? I don't remember that longer time being disproved.

Pants-of-dog wrote:

After asking jas and Fidel several times each about that very question, jas eventually confirmed that (s)he agreed with the collpase times that Greening calculated in his report.

Yes, writer. 10 - 13 seconds is generally agreed upon, with most people leaning towards 10 seconds. 10 - 13 seconds was the collapse time I quoted in the OP of the thread in which Pants first appeared. He questioned that time at first, but then found that Bazant's calculations confirmed this. I'm not sure why he's trying to present it as something that he introduced. He was merely confirming what I had already posted.

But, glad you're back, Pants. How about testing out this untested theory of yours now? Take us through it, step by step.

Not what I linked to, but has a counter: http://www.youtube.com/watch?v=ugypj1NsQ-A. I see that the NIST report does confirm the faster time period. So the doubters and NISTers agree on one thing, perhaps.

jas: It's not my theory. I don't have a dog in this one. Generally view it as a big distraction. But an interesting one.

No theory, just incredibly powerful: http://www.youtube.com/watch?v=yfce_C8GzdE

Pants, the one video has been pulled from Youtube (http://www.youtube.com/v/omzWzMLOfUI: "This video has been removed due to terms of use violation." — from what I can figure out, it was based on this original: http://video.google.com/videoplay?docid=2367902043037209880# — this video links to the following blog: http://undicisettembre.blogspot.com/2006/07/information-in-english.html)

Here's the second video I originally saw about time (when the talk was about a 9 second collapse): http://www.youtube.com/watch?v=qLShZOvxVe4

Still, all and all, I find myself far more drawn to — and compelled by — the moment, rather than all the theories that have spun out since. http://video.google.ca/videoplay?docid=1742836963699207403#docid=5474006...

writer wrote:

Haven't found it yet, but maybe this is of interest, Pants: http://www.youtube.com/watch?v=bMZ-nkYr46w

jas, do you remember the video I linked to a while ago? I don't remember that longer time being disproved.

That was a good video. Fidel and jas would probably like to watch it as well.

Fidel wrote:

7.7m/s is Garcia's instantaneous velocity at time of impact after a 3 metre fall. So, no, velocity is not constant. Acceleration is constant, the second derivative of distance with respect to time, but that is the nature of gravity as they say.

So, then why do you asume a constant velocity for your distance s?

Fidel wrote:

Once again, -7.7m/s is Garcia's instantaneous velocity at time of impact. Acceleration due to gravity is always constant. Gravity implies constant accleration unless the falling object is otherwise impeded, and which Garcia says was not the case. 250 steel columns provided negligible resistance to the falling "rigid upper block" according to Garcia.

This has nothing to do with Griscom's calculations. Rather than giving incorrect summaries of Garcia's position, can you please focus on the discussion of Griscom's numbers? Did Griscom also incorrectly assume a constant velocity?

Fidel wrote:

Well you've seen the math right here on babble. You just don't know how to react to it with none of Garcia or Bazant or NIST having commented for you to conjure up a coherent reply.

No, I have seen your math, which does not show that tilting hasanything to do with momentum transfer. My coherent reply, which you have ignored several times, is that you are incorrectly assuming a constant velocity.

Pants-of-dog wrote:

Jas posted a photo clearly showing corner lines of the upper block deforming to a large extent. I'll try to find it.

Please do and thank you.

I posted a larger version of the same picture that you posted here, if you wish to use it.

Fidel wrote:

Garcia's rate is not a constant velocity. Instantaneous velocity was explained to you above.

I know that Garcia does not use a constant velocity. You did. In your calculation for delta-t, you assume a constant velocity. Since You asume a constant velocity while Garcia does not, you can't be talking about the same thing.

Fidel wrote:

Yes, Griscom assumes Garcia's instantaneous velocity when calculating duration of collapse due to tilting. At this information can be gleaned by actually reading [url=http://impactglassman.blogspot.com/2007/01/hand-waving-physics-of-911.ht...'s Handwaving the Physics of 9/11[/url] essay.

After reading that essay for the fourth time, I still see no math at all showing how Griscom came up with his numbers. If Griscom assumes a constant velocity, which is not apparent from the essay, he is wrong as well.

Fidel wrote:

And this was laboriously explained to you several times as well. Both Griscom and I are using Garcia's [url=http://www.counterpunch.org/physic11282006.html]impulse momentum form of Newton's second law[/url] referred to in his Counterpunch essay. If you have issues with Garcia's equation for force balance, then perhaps you should either point out to us where he is wrong, or contact him yourself and point it out to him. Either way I am now convinced that you don't know what you're talking about.

I have no trouble with Garcia's work. I think that is correct. I think that you are incorrect (and possibly Griscom) because you use a constant value for velocity to find delta-t.

Fidel wrote:

.....

Manuel Garcia wrote:

Starting from rest at time t = 0, the block reaches a velocity of [url=http://www.counterpunch.org/physic11282006.html]v = -7.7 m/s at t = 0.78 s[/url]. The descending block makes contact with the topmost stationary floor of the lower structure.

No one is saying velocity is constant except for you. This is absurd.

....

I gave you the details for (delta)t=0.14s as confirmed to me by Dr. Griscom. You've since insisted that only by the calculus can dt be calculated. That's just wrong.

Griscom assumes the exact same instantaneous velocity at time of impact that Garcia does, which is -7.7m/s. You are confused perhaps with constant acceleration due to gravity, which is always 9800cm/s^2 on this particular planet in general.

...But you are having trouble. Do you understand what instantaneous velocity is? Here's a question for you: What does Garcia say that the instantaneous velocity of the descending upper block(South Tower) is after a 3 meter free-fall over 0.78 second?

Instantaneous velocity at the exact instant before impact is 7.7m/s downward.

The instant after that, there is a time during impact in which the velocity of the upper block changes. Garcia says this time is 0.01 seconds. You say it is 0.14 seconds.

Except you use a constant velocity of 7.7m/s to calculate that time. You take a vertical distance, divide by this constant velocity, and get delta-t.

Please note that during the actual impact and in Garcia's model, velocity changes.

In your model, velocity stays the same.

You make the error of using an instantaneous velocity as a constant velocity during the time of impact.

Here is an explanation of the relationship between impulse and change of momentum. Please note the change in velocity (delta-v).

Fidel wrote:

Pants-of-dog wrote:

Instantaneous velocity at the exact instant before impact is 7.7m/s downward.

The instant after that, there is a time during impact in which the velocity of the upper block changes. Garcia says this time is 0.01 seconds. You say it is 0.14 seconds.

Garcia says that the instantaneous velocity at time of impact is -7.7m/s after 0.78s of free-fall from a height of 3 metres. 1/100th of a second is the duration of impact during which several things happen:

Manuel Garcia wrote:

Impact is a very brief process whose duration is dt = 1/100 s. During the impact, energy ripples through the floor structure as elastic waves in the steel and concrete;[...] Within dt = 1/100 s, the floor structure has transmitted the force of the new load to its joints with the building's core and periphery.

Pants-of-dog wrote:

Except you use a constant velocity of 7.7m/s to calculate that time. You take a vertical distance, divide by this constant velocity, and get delta-t.

Please note that during the actual impact and in Garcia's model, velocity changes.

In your model, velocity stays the same.

Time to impact derives from s=Vot + gt^2/2

If we simply add Griscom's duration of impact time to Garcia's time to impact(0.78s + 0.14s), we get 0.92246 s and resulting in an increase in neg. velocity by 1.3m/s, which givies an instantaneous velocity of 9.04m/s. It still doesn't change the duration of impact enough(0.12 s instead of 0.14s) to matter to Garcia's force balance equation. The result will still be somewhere far below 6.1 times the static force. Plug dt=0.12 s into Garcia's force balance equation and note the result. I really do think you are hopelessly confused and should be confirming that fact with someone who knows something about math and physics.

Fidel, what is the difference between v and delta-v?

jas wrote:

Not at all. You were trying to assert that truthers were saying the buildings fell in absolute free fall, and you spent three threads "proving" that wrong and wasting everybody's time. Throughout that thread and all the others, I have always said "near" or "within seconds of". There is no possibility you could confuse what I was saying. You either weren't reading properly, weren't understanding what you read, or you were deliberately misrepresenting the truther argument for some rhetorical purpose which remains unclear. I suspect you realized halfway through your argument that no one was arguing with the collapse times that Bazant based his model on.

If people want to know what I meant, they can read my words themselves.

jas wrote:

We have already shown how Bazant and Greening violate basic laws of physics in their silly model.

No. You have not.

You have repeated this claim many, many times in this thread. You have never successfullly argued it.

jas wrote:

It's time for you to show that it works. Tell us what is happening mechanically in the crunching down between C and A, B and A, then B and C, give us the timeline, and what the properties of C are before and during collapse. Thank you.

<snip Bjorkman's simplistic and incorrect model>

Bjorkman seems to have left out the impact zone entirely.

The impact zone is the line between C and A. He leaves C the same size, unlike what we see happening in the videos, but he doesn't need C to shrink in size in order to show how absurd this model is.

Bjorkman's illustration makes obvious what is wrong with the model, Pants. You can't have a smaller something crunch through a larger something of the same material--in the case of a building, for much more than a few floors. There is no precedent in nature or engineering that would support this model. Bazant's math is made up to legitimize what is illegitimate scientifically.

A house of cards?

So, a few cards fall, pulverizing the rest? I haven't seen this.

Please try to get your analogies somewhat in the same universe. It was the same thing with you trying to compare a building with a tripod that loses one of its legs. There's simply no comparison.

Pants-of-dog wrote:

siamdave wrote:

- just came across this - puts Garcia et al in their places pretty good, in terms of talking about physics and other things related to reality, rather than the NIST et al fantasies applicable only somewhere down the rabbit hole where the red queen makes the rules - http://heiwaco.tripod.com/nist0.htm .

Please quote the relevant text of Bjorkman.

Big chuckle - that's amusing, Pants, the guy takes apart your entire "theory" from beginning to end, and you say 'please quote the relevant text... ' - you must be good with the kids at Xmas who are starting to wonder about Santa - "Well, the cookies were there when we went to bed? - yea..- and they were gone when we got up? - yea... - and can you prove Santa did NOT come? - noooo' - voila, case proved! - and now you must prove me wrong, or accept my 'facts'!!

Pants-of-dog wrote:

jas wrote:

... Yes, writer. 10 -

{post 19} You seem to be confused about what I was posting in that first thread. No matter, as people can read it for themselves... I will give you your long and detailed explanation as soon as you do one thing: you have to successfully show me that Bazant or Greening or the NIST have violated a law or principle of physic in their model of the collapse.

- if I might - the anti-science nature of everything to do with the OCT prompts me to respond here - it's not a question of what laws of physics or science you have violated, it's getting an idea of what laws of science the official conspiracy theory actually follows. Allow me to demonstrate - it's not challenging:

1. They use the 'legal prosecutorial' method rather than anything that would be called 'scientific' laws or methods of (real) physics. When faced with a new or unusual phenomenon, the scientific method involves gathering **all relevant** factual data, formulating realistic hypotheses that explain the observed phenomenon, testing them, etc. The admitted method used by Bazant and all OCTers following was to postulate a model on very limited, preliminary data, again saying right up front they are NOT going to even consider the most likely hypothesis (based on Occam's razor etc principles - if it looks like X, behaves like X, probably it is X), then selectively gather and interpret 'facts' to fit that solution, very often in the process making wild exaggerations and completely unjustified assumptions to justify their theory, along with failing to consider (or simply lying about) basic facts concerning the WTC towers and highrise construction in general. That more Americans and other people do not understand this does not lend credence to the 'theories', any more than jungle savages thinking a modern firearm is 'magic!' proves magic exists. Major violation of the most basic scientific principles right from the getgo. Things founded on lies and misdirection and deception are highly questionable by definition, and surely have nothing to do with real science and physics.

2. For one quite brazen example, all of these "theories" point to, and heavily rely on, "evidence" indicating that at some times, some localized fires MAY have reached temperatures at which steel can become compromised if the steel itself reaches those temps - and then make the astounding assertion (assumption) and leap that therefore all of the steel in a certain very large area was thus compromised, leading to the instantaneous failure of all of the columns that were not directly breached or damaged by the initial impacts. A wild exaggeration, very blatantly so, something no impartial scientist honestly engaged in trying to figure out what happened that day would ever make, but necessary to justify their pre-conceived model. For example, there is no visual evidence at all that most of the outer columns, visible throughout the period between the plane crash and collapse, ever reached temperatures anywhere near hot enough to compromise them. None - indeed, all visual evidence, of which there is a lot, would indicate that most of these columns stood tall and strong until the collapse was initiated through some as yet undetermined means. To assert that all of these outer columns reached temperatures hot enough to compromise their strength, at the same point in time, and thus all collapsed together, is completely contradictory to both reason and actual observation.
**There is no mention of the inclination of steel to conduct heat away from the source of the heat which would make the attaining of such temperatures in any single spot, let alone in dozens of central and a couple of hundred outer, columns very, very, very difficult in that huge steel matrix,
** there is no mention that there were at least 30 central very large and solid steel columns remaining after the crashes that would have had to reach this high temperature,
** there is no attempt to explain how long steel has to be exposed to what temperatures to start to approach its weakening point,
** there is no attempt to explain how long a length of all of those columns would need to reach some failure point before it buckled or disintegrated,
** etc and etc and etc.
(I'm not even getting into the loss of fireproofing here, so down Rover - if the fires are not hot enough or sustained enough to affect bare steel, which is what the temps all refer to and is no more 'proven' by wild assumptions than Santa Claus, then whether or not the fireproofing was dislodged is just another meaningless red herring - the fireproofing only matters if the purveyors of the theory have demonstrated with some believability that the fires were hot enough for long enough to affect even bare steel in all of those columns, which they have not begun to do.)

The 'progressive collapse' theory completely fails on this point alone, as if the 'initiation' is proven to be impossible, there could hardly be 'progress'. In thinking about the scenario as I describe it above, I don't need to show you where 'the laws of physics' and/or science were not followed - you need to show us where, in any instance, they actually were followed ...

3. Again, all of these theories begin with some version of this (from Greening): "..We consider the initiating event of a WTC tower collapse to be the failure of crucial steel support structures at the appropriate upper floor level of the building, followed by the free fall of the entire upper block of n floors through a distance hf = one floor height = 3.7 meters..."

Really. Now that is one hell of a "consideration", and the two major things it states as necessary prerequisites for the entire following "theory" stand up to no scienctific reasoning at all. It's very telling that NONE of these people mention any actual numbers of columns, but use words designed to obfuscate - 'many columns' were damaged, 'the remaining' columns could not take the 'overstressing', and etc. The theory would sound a lot different if numbers were used - "The plane crashes breached some 30-60 (depending on building) of the ~250 outer columns, leaving most of them intact and undamaged; as for the inner columns, we can not be sure, but the best estimates indicate that 5-15 of the 47 inner core columns were breached or damaged, leaving a minimum of 30 of the 47 inner columns standing to bear the weight of the building, in a huge steel matrix along with the remaining outer columns and 110 floors of cross-bracing...' - wow, sure leaves a different impression than the one left by the OCT - but if your underlying purpose is to create and encourage belief in a sense of impending doom, quite obviously the use of real numbers would not further your cause, indeed would be quite inimical to it.

But that is just a preamble. Again, let's look at numbers a bit more precise than 'a few were left' - actually, let's say that 35/47 columns remained after the crash, all part of that 6x8 column, 1100-ft tall cross-braced matrix - that's a lot of strong steel - it is an apparently intentional misdirection of the OCT to attempt to give the impression these columns stood alone, rather than as part of a great matrix. Another extremely dishonest thing all of these theories do is attempt to pretend the fact of 'redundancy' does not exist, but of course every steel skyscraper is built with some amount of redundancy, so when one structural element fails, and the load is transferred elsewhere, there is not an automatic 'overload', as these theories attempt to give the impression. If a column is designed to bear 100 pounds, but it's actual load is 50 pounds, then adding 10-20 or even 30-40 more pounds is not 'overloading' it, just bringing it closer to its design load. Why would 'real' scientists, trying to explain the collapse of the twin towers, not talk about this *fact* openly? Obviously, the job of these OCT-selling apologists is not real science at all, but to justify the 'total collapse' rather than get involved with explaining why it should *not* have collapsed - and even acknowledging this redundancy would make their job very, very difficult, and probably, in consideration of everything else they obfuscate or lie about, well nigh impossible. Especially when you start adding in over 200 outer columns, all sharing the weight of the building after the crash damage with the 30+ inner columns, with no demonstrable fire exposure for certain on most of the outside - no reason at all for all of that steel to just 'collapse' en masse. No reason at all. Again - up to you to show me where the 'physics' or 'science' is here in all of this obfuscation to the point of lies - its absence is quite obvious.

Which leads to the 2rd 'consideration' of Greening et al which is completely unjustifiable - "...the free fall of the entire upper block of n floors through a distance hf = one floor height = 3.7 meters...." - I won't bother wasting much time on this - what I have explained before should make it completely obvious that there is simply no possible way, given the conditions and situation of that day, that all 30-40 of those undamaged inner columns, plus over 200 of the outer columns, none of them anywhere near the point of collapse or in any way 'overstressed' or heated to the point of collapse, are going to all just give way at once after small fires burning less than an hour, allowing this totally impossible 'free fall of 3.7M'. No way, and to try to postulate and defend this position is just to completely disengage with reality and science, and it's difficult to justify wasting much time talking with those who try to defend this fantasy, you're really the flat-earthers of the early 21st century, and your completely unscientific and dishonest approach to your arguments in your desperate attempt to defend an untenable position demonstrates that quite clearly (that you appear to be in the majority is not relevant - the original flat earthers were also a majority for quite a long while, and the powers-that-be of the time quite aggressive in defending their 'theory' of the celestial bodies and discouraging any challenges).

4. I shouldn't go around shooting dead horses, but let's try to finish this once and for all, as it gets tedious. Let us assume even for the sake of argument that by some magical intervention all of those ~250 columns just disintegrated all at once, and your upper block actually did fall through 3.7 meters in 'freefall' - is that going to cause the type of total collapse we saw on that day?

Not in a million years, at least outside of Hollywood FX.

**first, you do not have a stack of plates to 'pancake', as your theory tries to make a case for (I know you don't call it pancaking anymore, but that is quite clearly the scenario you try to establish) - you have an 1100-foot tall central core composed of a matrix of 47 cross-braced columns, surrounded by an 1100-foot tube of very strong steel, again cross-braced every few feet. The 110 floors are attached every 10 feet or so all the way up between the central core and outer tube, actually increasing the strength of the overall structure by acting as yet more cross-bracing. If you want to assume that some magical space ray instantly severed a section of this structure, leaving a 10-20 upper-floor section, and this upper section dropped en masse to the lower, this tube-within-a-tube is the basic structure you would be dealing with. So you would not have an upper section dropping onto one floor and overwhelming it, and again and again until it all hit the ground, you would have a 20-story steel tube-within-a-tube dropping onto an 80-story steel tube-within-a-tube, and any imaginings of what that would result in must be based on that reality, not the very misleading 'solid upper block dropping onto a poor old weak single floor' scenario of the OCT. And what is going to happen then? The tubes, the main structural framework, are going to meet - either the upper section drops straight down so the outer and inner columns meet directly, or they are going to be off-center, and some off-center meeting is going to occur, with some number of the upper columns meeting some number of the lower columns - it's going to be a train wreck, but it's not going to be 'global collapse'. (What happens to the cement floors stretching from core to outer columns is pretty irrelevant here, as they will be unable to support much weight and will tend to crumble if any great weight is placed on them. They will, of course, come into play as the two sections reach for their final equilibrium, as cement and steel is obviously not without some strength and resistance, but any individual floor is a small player when considered against those massive inner and outer tubes.)

Think as a scientist, or intelligent layman, rather than someone attempting to justify a collapse theory - if I have a stack of those grey egg trays, lift a few up and drop them - no big spectacular collapse. If I drop a big cement block on that stack, it would smash them up pretty good, of course. But if I dropped that cement block on some other cement blocks - it might chip a couple, but no big global cement block collapse. Likewise the WTC buildings - sure that upper 20 stories of steel and cement looks pretty impressive - but if you drop a 20-story steel and cement structure a few feet onto an 80-story structure of the same stuff, you are NOT going to cause that lower structure to instantly disintegrate - it is made of the same stuff you are dropping on to it, and it is a lot bigger, and it is by god very, very strongly built - it's not going to disintegrate! - it's hard to talk to people who do not understand this rather basic fact of the way the world works, and demand I go and dig up some mathematical equations to demonstrate the obvious because they by golly have constructed some 'equations' to prove the ridiculous, but there it is. We have modern people calling themselves 'economists' doing the same sort of thing, but morning eventually comes to everyone, and the daylight sends the dreams away. You can dick around with distractions all you want, but in the end, you cannot dick around with the way the world works. You can convince the unsophisticated natives that your modern rifle is a 'magic stick wah wah!!' - but that does not change the basic scientific facts of how it actually works, and if you come back to Canada and wave your arm around shouting booga booga and telling the natives you are a great god with Magic Progressive Collapses - well, at least some of us wonder what the hell you are actually trying to prove here. It sure as hell has nothing to do with real science and physics.  

(for a very thorough and scientific 'debunking' of the 'math' and 'physics' of Bazant, Greening, Garcia, Pants et al - http://www.journalof911studies.com/articles/Article_3_RossReply.pdf .)

Fidel wrote:

Pants-of-dog wrote:

Fidel, what is the difference between v and delta-v?

Sure thing. If we use F=ma, the concrete slab of mass m falls at speed v when impacting the concrete slab below.. ...

No. You are simply wrong here.

F=ma does not give us an object with mass m falling at velocity v.

It gives us an object with mass m falling at a constantly changing velocity delta-v.

Pants-of-dog wrote:

You never mentioned pulverisation before. And now you are.

Why do you shift the proverbial goalposts?

I've never mentioned pulverization? LOL. I think even Yiwah can tell you you're wrong, But no matter. Does this ruin your house of cards analogy?

I've got to say, pulverization is and has been one of jas's main points.

Fidel wrote:

That video is in itself a straw man argument. Of course, the gubmint guys won't acknowledge what truthers are actually saying:

ae911truth.org wrote:

[url=http://www2.ae911truth.org/downloads/29_Structural-Civil_Engineers_2009-... Fires Vs. Explosive Events[/url]
Though four official accounts blame fire for the destruction of all three World Trade Center towers, the fires do not appear to have been particularly severe.
NIST states that the jet fuel burned off in just ten minutes.7 "They also acknowledged that office furniture burns for only 15 to 20 minutes in any one
area" before it's consumed,8 Scott points out. "There's ample evidence that the steel temperatures got nowhere close to the "600+ degrees Centigrade [1,200 degrees Fahrenheit] required to cause failure." We saw no "raging infernos" on TV, David Huebner, P.E., points out. Sooty smoke and dull red flames, Scott says, indicate "cool fires ... fuel-starved fires." Firemen at the 78th-floor impact zone reported "only two small fires," Scott adds, "not the 1000 degree-Centigrade inferno" government officials claim. New York Fire Department (FDNY) personnel, trained to assess fires' structural hazards, had no reason to expect total collapse, Brookman writes. Scott notes that several steel-framed towers have burned longer, hotter - and much more intensely without collapse. "As engineers we know what fire can do to steel and what it can't." "Over 100 recorded witnesses reported hearing and seeing multiple explosions," Rice wrote.9 Brookman cites "numerous eyewitness accounts, including the FDNY oral histories, of secondary explosions ... well below the impact floors."

Firefighters and emergency workers heard "explosions" below the impacted floors. And there were many more first responder observations which must be ignored by the feds in order that their fairy tale surrounding 9/11 remains intact and unscathed by truth seekers skeptical of the official 9/11 narrative - that same fairy tale which the undiscerning accept without question.

Of course, the eye witnesses to these events were just people. And we know what rightwing hawks think of every day people in general - they wouldn't spit on us if we were on fire(or made homeless by a hurricane that devastated New Orleans).

http://firefightersfor911truth.org/

Nice strawman argument. I especially liked the irony of you accusing the video of being a strawman.