North Tower Acceleration

[wildbilln864]

a video showing the acceleration of the tower as it collapses by David Chandler.

&NR=1&feature=endscreen

[William Seger]

1. Chandler is an idiot

Chandler: "On this kind of a graph, a straight line indicates constant acceleration."

What's wrong with that statement, wildbill? If you can figure our what's wrong with that statement, you'll also know one reason why his entire argument fails, badly, but there is actually a second reason, just as good.

What's truly pathetic about the stupidity of this argument is that Chandler is one of the few AE911truth guys who even attempts to make technical arguments.

[OnTheOtherHand]

2. aw, shit

That sentence wouldn't be bad if he was simply trying to explain a velocity graph. What he actually tries to do with it is bewildering.

Let's see, am I getting this right? (1) The "upper block" is falling at 0.64g, which means that the downward force it exerts on the rest of the building is 0.36g, so it is exerting less force on the rest of the building than if it were standing still. (2) The acceleration is (purportedly) constant, which means that the rest of the building isn't exerting any resistance.

Is that really, more or less, what he said?

[wildbilln864]

4. you must have been up too late also

nt

[OnTheOtherHand]

6. because I posted at 10:11 AM?!

Look, it's OK with me if you aren't interested in discussing the catastrophic events of 9/11, but then what is your point?

[William Seger]

7. More or less

It's actually hard to untangle what he says, but the apparent argument is that columns which had been designed to hold 300% of the weight above them were only providing a resistance of 64% of the weight, which implies (ta da) controlled demolition.

[OnTheOtherHand]

8. the mind reels

He can't even seem to decide whether or not the lower part of the building is providing resistance. Apparently, the "constant acceleration" is supposed to prove that it isn't, even though it is at less than g.

[wildbilln864]

3. up late there william?

You tell us what's wrong with it william.
His argument doesn't fail, yours does however!
How would that graph look if it did represent constant acceleration in your opionion?

[William Seger]

5. Here's what's wrong with it:

Last edited Wed Dec 28, 2011, 12:44 PM - Edit history (1)

A constant acceleration would produce a straight line on that velocity graph, yes, but imposing a straight line on measurements every 0.2 seconds, with no indication of the error in the measurements, cannot tell you with any accuracy that the acceleration was really constant. You might say it's approximately constant, at some scale, but the difference between that and truly constant gets you into trouble if you try to apply that over-simplification the way Chandler does to say that the resistance of the lower structure was only 36% of the weight of the upper structure. Tracking the roofline falling is to track the aggregate result of thousands of individual failure events, and the acceleration that Chandler is measuring is just the AVERAGE result of all of them. In failure events where a column buckled, there is no reason to think that, locally, the acceleration was anything resembling constant: The column only provided it's maximum resistance for a few inches of downward deflection, followed by rapidly decreasing resistance (and increasing acceleration) as the column went into plastic deformation and buckling, possibly followed by zero resistance (and local free-fall) if the column broke. If all the column failures were due to buckling, then all you could say from Chandler's measurements would be that the columns allowed an AVERAGE acceleration of 64% g through that entire fall to the next floor, not that the column only resisted 36% of the weight. In fact, we know that most columns did not fail from buckling, and that's the second problem with Chandler's argument: Most columns were simply pushed aside after the floor structure was ripped away from them. Again, the maximum resistance was only for a few inches of floor and column deflection, at most, followed by zero resistance (and local free-fall) once the floor broke free, so that's certainly not a constant acceleration, either. Chandler's 64% g, then, is the net AVERAGE of everything from the acceleration through maximum column resistance to free-fall, but by inaccurately claiming constant acceleration, Chandler uses it to claim that the maximum column resistance was only 34% of the weight. It's an idiotic argument.

[cpwm17]

9. Try this analogy

Place a 10lb weight on top of a 1ft stick that is capable of supporting 20lbs without buckling and breaking - so far so good.

Now lift that 10lb weight 1ft above the top of the stick, and place it on top of another similar stick connected to the first stick. The weight will be 2ft off the ground now. Now break the top stick, which will drop the 10lb weight on top of the lower stick. What do you think will happen?

The weight will accelerate through the lower stick and break it. The weight will hit the ground a little slower than if the lower stick wasn't there at all - let's say at 90% of free fall speed. The 10lb weight would then average .9g acceleration

By David Chandler's logic, the lower stick only provided .1W (1lb) resistance, which means that the weight only provided .1W (1lb) of worth of force. Since 1lb is 90% less than 10lbs, the lower stick must have been broken by some other means - perhaps an explosion.

He then goes into some nonsense about its constant acceleration - and whatnot.

My analogy isn't perfect. As the towers collapsed, the falling sections gathered more mass from the lower sections of the building as they fell. The mass from the lower sections of the buildings started at an initial zero velocity, which slowed down the acceleration of the falling sections.

[wildbilln864]

10. damn that's funny there!

thanks for the laugh!
ironic you post such nonsense and the go on to call a physics teacher's efforts nonsense. thanks again..

[OnTheOtherHand]

11. so you have no rebuttal whatsoever?

Good to know.

[wildbilln864]

12. no need for me to rebut nonsense!

the rebuttal is in the videos!

[William Seger]

13. No it isn't in the videos

If that's your only response, I don't believe you really understand what the video says OR the arguments you've been given.

Prove me wrong by stating both in your own words, and then try to substantiate your claim that "the rebuttal is in the videos!"

Oh, I forgot: You're not under any obligation to prove any of the, uh, "truth" you post.

[wildbilln864]

14. Sure it is!

I cannot help that you can't/won't see it!
Believe what you will but don't piss down my leg and tell me it's raining.

[OnTheOtherHand]

15. so you're demanding that we should take your word for it?

Why should we? If you made an argument, we could assess it -- but if the best you can do is to assert that someone else came up with an argument for you, well, would you buy that if I tried it? I don't think so.

cpwm17 took the time to write a serious response to your comment. If you've got nothing, you've got nothing.

[wildbilln864]

17. I demanded nothing!

nt

[OnTheOtherHand]

18. oh, that's a fair point

Posting unsupported assertions may undermine your credibility, but you have never demanded to be treated as credible. I just don't see the point in it.

[William Seger]

16. "can't/won't see" what?

You're not quite sure about that, are you? If you can't describe this "rebuttal" you see in the videos, maybe it's a figment of your imagination, huh?

[cpwm17]

33. You think David Chandler sounds intelligent

But you don't understand what he's talking about. That's why you can't post a rebuttal to my comment.

David Chandler's physics is way off. He doesn't indicate that he understands the collapse, or even basic physics.

[T S Justly]

19. Good video! It's certain to generate snark and slander and not much else by way of rebuttal. K&R (nt

[zappaman]

20. Great post!

Try reply #5 for starters.

[T S Justly]

21. A paragraph break, here and there, would have made it ...

Less nonsensical on its face. If the poster wants to redo his scree to make it
more readable, I'll give it another try.

* clerical edit

[OnTheOtherHand]

22. really, that's the best you can do?

You can't read it because you can't decide where the paragraph breaks should go? And that makes Seger's post "nonsensical on it's (sic) face"?

[T S Justly]

28. Lol! An oversight, perhaps? (nt)

Last edited Thu Dec 29, 2011, 02:04 AM - Edit history (1)

[William Seger]

29. I'll try to dumb it down for you, then

1) Chandlers measurements do not (and cannot) support the assertion that the acceleration was constant.

2) There is absolutely no reason to expect that the acceleration was constant, given that no conceivable failure modes would produce that result, even if it was a controlled demolition. (It's actually kinda funny that Chandler just blows right past that minor problem with his theory.)

3) If the acceleration was not constant, then Chandler's inferences about the maximum resistance being 36% of the weight are ridiculous, and that make him look rather like an idiot.

4) I can't think of anything less relevant to the issues than your inability to even comprehend what I'm saying. If you want to "give it another try" then good luck, but if you still don't even understand it, perhaps you should consider not responding.

[T S Justly]

30. Thanks, I think. Lol. But the video still trumps nonsensical Bush Era "science". (nt)

[zappaman]

31. I dun seen it on da videos! n/t

[T S Justly]

32. Lol, but yes. The videos have laid waste to Bush and his doctrinaires' output. (nt)

[William Seger]

34. I'm sure Chandler appreciates your unconditional support

... and it's always interesting to get some insight into who is falling for his nonsense.

[T S Justly]

35. Rather, it is I who supports Chandler's video evidence of NIST/Commission fraud ...

And, it is those who support, or pretend to support, the Bush administration's preposterous hoax who are "falling for" nonsense. That's in quotes because I think in some cases, proponents
of the Bush administration's hoax theories know full well the extent of the 9-11 fraud. However, I'm satisfied that you're not among that group, William.

[William Seger]

36. Most of what we know about 9/11 didn't come from the "Bush administration"

... and virtually NONE of what we know about 9/11 came from the "truth movement." As someone who supports Chandler's nonsense even though you don't understand it, you're hardly in a position to be taken seriously when you accuse thousands of people of being accomplices to a mass murder, without a shred of credible evidence. Since you call Chandler's nonsense "evidence" I'm not at all sure you know what the word means.

[T S Justly]

37. Most of what we know about 9/11 didn't come from the "Bush administration" - Lol, that is true. (nt)

[wildbilln864]

23. post 5 is just opinion!

supported by?
more opinion!

[OnTheOtherHand]

24. bullshit

Take this:

Imposing a straight line on measurements every 0.2 seconds, with no indication of the error in the measurements, cannot tell you with any accuracy that the acceleration was really constant.

Whether you know it or not -- whether you care or not -- that is a factual statement.

[wildbilln864]

25. he did not impose the line it...

was what the data points plotted.
what may I ask would have been the correct way?
No it is seger's opinion! Where is seger's corrected graph?

[OnTheOtherHand]

26. have you watched Chandler's video?

Chandler says, "as long as the top section of the building is in uniform downward acceleration, it cannot possibly be providing sufficient force to destroy the building."

But has Chandler proven that the top section of the building is in uniform downward acceleration? Hell, no. His points don't even form a straight line, although they're pretty close. (Of course Chandler imposed that line; if you connected different dots, you'd get a different line. Again, fact, not opinion.)

If Seger estimated Chandler's measurement error, you would say that was just opinion -- and you might even be right. But if you construe that those points are pretty much in a straight line, then you can start to get a feel for the problem by sketching (or imagining) lines connecting each pair of adjacent dots. For instance, in the screen shot I just took, one circle is about 14 pixels below the one to its left, and about 32 pixels above the one to its right. So, one line will be about twice as steep as the other.

For Chandler, apparently, an apparent doubling in acceleration is within the range of measurement error -- and it probably is. I'm certainly not convinced that the actual acceleration of his reference point changed in that fraction of a second; maybe it did, maybe it didn't. But if an apparent doubling in acceleration is within measurement error, then how could anyone say that the top section (or even his reference point) is in uniform downward acceleration?

[jesters]

39. general reply:

One need only view the videos of the tower's descent to understand the absence of the necessary deceleration. Mapping it out on a graph is basically just spelling it out in crayon for those who can't see that an under-15-second plummet to the ground with massive expulsion of matter all the way down is not possible gravitationally for a steel-framed, highrise superstructure.

The other point being entirely missed here is that in order for the upper portion of building to exert the kind of force that can destroy as well as completely pulverize the much taller, heavier and intact lower structure it would need to decelerate (to use the lay term). Visibly. You can't have that kind of force exerted without visible decelerations. This would be multiple punctuations in the building's descent, most likely resulting in collapse arrest before the ground is reached.

This isn't difficult, folks.

[OnTheOtherHand]

40. it's certainly more difficult than that

You can't actually rebut previous studies of the collapses by saying, nuh-uh. An under-15-second collapse "is not possible gravitationally"? Why not?

The upper portion of the building doesn't have to "destroy as well as completely pulverize the much taller, heavier and intact lower structure." The upper portion isn't the only thing that falls.

[jesters]

42. "The upper portion isn't the only thing that falls."

You apparently don't understand the collapses. Nor what the official collapse explanations are.

[OnTheOtherHand]

47. srsly?

You think that the upper portion is the only thing that falls? And you think I'm the one who doesn't understand the collapses and the official explanations?



Care to try again?

[cpwm17]

41. Expulsion of matter is much greater for larger, taller buildings

As you scale up the size of any object its strength to size (and mass) ratio goes down. This means that there is a lot of stress on large, tall buildings. So during a collapse of a large, tall building, depending on its construction, there is a lot of potential for a rather violent collapse. The towers weighed around 500,000 tons. There is a lot of potential energy being converted to kinetic energy during the collapse. That's the energy of a very large bomb.

The only way for there to be any deceleration during the collapse would be for the resisting force of the intact section of the lower block to be greater than the force of the falling upper block striking the lower block. That certainly didn't happen during the collapse. The lower block only slowed down the acceleration of the upper block's mass. The force after the upper block's mass fell a dozen feet between the floors is far greater than the resisting force of the intact section of the lower block. So it must accelerate all the way down, especially after the debris between the blocks increases during the collapse which provides more mass to accelerate the collapse.

[jesters]

43. "The lower block only slowed down the acceleration of the upper block's mass....

"...The force after the upper block's mass fell a dozen feet between the floors is far greater than the resisting force of the intact section of the lower block."

First of all, the upper portion was never in free fall. (In fact, haven't 9/11 "debunkers" spent ten years arguing this very point??) So that is a deliberate miscalculation right off the bat. Secondly, and this apparently needs to be repeated across the internet: For the upper portion to EXERT THAT FORCE would REQUIRE IT TO DECELERATE. IF IT'S NOT DECELERATING, IT'S NOT EXERTING A FORCE. Because there's nothing to exert it against.

"So it must accelerate all the way down, especially after the debris between the blocks increases during the collapse which provides more mass to accelerate the collapse."

You're just repeating Bazant's cartoon model which has largely been discarded by both sides of the debate now. No, it would not accelerate all the way down. There's no model that has been put forward anywhere that can explain a debris-driven, top-down destruction (and pulverization) of an intact steel-framed skyscraper. If you know otherwise, please refer us to it.

[Bolo Boffin]

44. "Bazant's cartoon model which has largely been discarded by both sides of the debate now"

Really? "Both sides"? Sounds like hyperbole to me.

[AZCat]

45. "IF IT'S NOT DECELERATING, IT'S NOT EXERTING A FORCE." Really?

Anything less than an acceleration equivalent to the local gravitational constant is an indication of an opposing force. After all, m*a = the net force on a body. Struggling with the concept? Try drawing a free body diagram of the upper portion.

[jesters]

48. Yes, really.

1) We are talking about the smooth motion of the upper block in its initial collapse stages. No visible decelerations as it meets the stronger, intact lower block. Indeed, it destroys itself. Where does the core structure go?

2) We are talking about a force that needs to destroy all the connections of 80 - 90 intact steel-framed stories, while pulverizing all contents at the same time, at the average rate of 0.17 seconds per floor. The upper portion of building does not have this energy through gravity. How could it? It did not free fall during collapse initiation. It did not free fall at any time. Right there, it does not have the energy to complete collapse, and it only loses energy through each successive floor gravitationally, as it must. On top of this, you are requiring it to pulverize all the building contents at the same time. This is never going to happen gravitationally. Further, the top portion has destroyed itself in the first three seconds of collapse. Where is the model for a debris-driven, top-down, total destruction of a steel-framed super highrise?

Please include in your reply an answer to the last question.

[AZCat]

49. I don't think you responded to my concern.

You haven't explained your claim that no visible decelerations means the upper portion is not exerting a force on the lower portion. This claim is not compatible with basic physics principles.

Your #2 is nonsensical. A rational reply is not available.

[jesters]

50. AZCat says:

"You haven't explained your claim that no visible decelerations means the upper portion is not exerting a force on the lower portion."

As I stated in the very post you are replying to:
[quote=jesters]... 2) We are talking about a force that needs to destroy all the connections of 80 - 90 intact steel-framed stories, while pulverizing all contents at the same time, at the average rate of 0.17 seconds per floor. [/quote]

You are attempting to suggest that the 30% resistance provided by the bulk of the intact structure, which, by standard engineering, was capable of providing 300%, is due to gravity acting on the upper block. This point of view apparently does not understand that the force exerted in this instance, as measured by the resistance seen, is not enough to destroy the building, even if it did initially drop in free fall (which it didn't). Not to mention that the upper block destroys itself in the first few seconds of collapse.

"Your #2 is nonsensical."

I've now explained it twice. What part don't you understand?

And can you point us to a credible model of a debris-driven, top-down total destruction of a steel-framed super highrise?

[OnTheOtherHand]

51. moving the goalposts?

It is not the case that the upper portion needs to "destroy all the connections... while pulverizing all contents." But even if it were, the question remains whether you stand by your assertion that "IF IT'S NOT DECELERATING, IT'S NOT EXERTING A FORCE." You can't explain that claim by repeating the other claim.

[AZCat]

52. OnTheOtherHand's post is correct - you still haven't supported your claim.

Please provide an explanation. A properly labelled free body diagram would be acceptable in lieu of a narrative.

[jesters]

53. What a cop out.

I've already asked you: What part of this don't you understand? Can you at least answer that?

Do you think the force you need to destroy the building can really be applied in a situation where the small top portion is sinking through a larger lower portion (using Bazant's piledriver model) that is providing only 30% resistance to free fall? How high are you dropping this block from, lol? And, oops, what happens to the upper block anyway? And why do you think that is?

I mean, what fantasy are you living in here? Answer my question.

[Bolo Boffin]

54. I don't see the problem with you providing a properly labelled free body diagram

to put numbers onto your point.

Can you do that?

[jesters]

55. Maybe.

Do you really need one to understand this concept?

Do you know of other kinds of collisions between similar bodies where decelerations do not occur?

[Bolo Boffin]

58. You "maybe" can provide one.

Well, if you can, please do.

I personally don't see the issue. Bazant Zhou (which, despite your assertion above, no one outside of 9/11 Truth has discredited) shows that the upper section would have had ~31 times the energy necessary to overwhelm all structural support below. Even you admit that the upper section is only accelerating at 70% of freefall. That other 30% is going somewhere - that energy is doing something.

Basically put, 9 times the energy to overwhelm the lower structure completely is not present in the descent of the lower section. My answer would be it's going to tear apart the lower structure and pulverize building contents. Your milage may vary.

Also, there is no reason to think that each individual collision between the upper and lower section would propagate to the top of the upper section. Since they are not rigid blocks but complex structures hitting each other off-center, any expected "jolt" would actually only be seen at the point of contact, ripping one or the other structural element loose. And after the center debris field was developed, no such jolt should even further not be expected.

[jesters]

59. "Bazant Zhou shows that the upper section would have had ~31 times the energy necessary

Because they assume free fall during collapse initiation, ignore Newton's third law in the subsequent collisions, and (later) invent a magic carpet of rubble that the fictional upper block rides all the way down to the ground before getting eaten by it at the end.

Are you seriously using this model?

[Bolo Boffin]

60. You seriously are not understanding what Bazant-Zhou is doing.

Bazant Zhou is a limiting case, using the best case scenario for WTC tower structure survival, and still the building falls. This is of immense importance to understanding why total collapse was inevitable after collapse initiation. It lays a framework for speaking about and understanding all similar types of collapse.

Where do you think the kinetic energy not being used to accelerate the upper sections is going and doing, jesters?

I take it you refuse to offer the properly labeled free body diagram that has been asked of you.

[jesters]

67. Absolute B.S.

"Where do you think the kinetic energy not being used to accelerate the upper sections is going and doing, jesters? "

This is a bizarrely phrased question. What extra energy are you referring to? The only energy available to pull the top section of building through the lower is through gravity. Bazant and Zhou assume a free fall initiating impact which did not occur, and then ignore the absorption of kinetic energy by the lower, much more intact, much larger structure. That's where they get their "inevitability", their "overwhelming" force. This is hardly a best case scenario. It's a fabrication. The best case scenario for collapse arrest is reality: the buildings remained standing after the plane impacts. Were it not for incendiaries, they would have remained standing or at most suffered partial collapses in the upper portions.

Bazant's model has been shown to be wrong by numerous independent analyses, on both sides of the debate.

[William Seger]

73. You have absolutely no idea what you are talking about.

Bazant's analysis IS an energy argument: It calculates how much energy the falling mass had and how much could be absorbed by the lower structure. I really don't understand why "truthers" think it's okay to slander one of the country's leading theoretical structural engineers without having the first fucking clue what he's even doing in that analysis.

And, btw, Bazant assumed one story of fall because that's the minimum possible. In fact, the initiating event was the floor pulling the perimeter wall in until it buckled, not buckling between floors, so the initial fall was really two stories rather than one. Furthermore, Bazant's calculations can be worked backwards to show that a fall of only about one foot would have put more impact energy on the lower structure than it could absorb. As Bazant says in a later paper, that's all a structural engineer needs to know.

> Bazant's model has been shown to be wrong by numerous independent analyses, on both sides of the debate.

Utter bullshit. Bazant's model has only "been shown to be wrong" by the kind of imaginary physics and hand-waving assertions that you're tossing around, and generally by people who know as little about the analysis as you. Out in the real world, it appears that Bazant's analysis is well accepted among those who actually understand the subject.

[jesters]

75. "Bazant's analysis IS an energy argument" ...

" It calculates how much energy the falling mass had and how much could be absorbed by the lower structure."

No, it does not.

And I love how you brush over his assumption of free fall in the initiating collapse.

"Bazant's calculations can be worked backwards to show that a fall of only about one foot would have put more impact energy on the lower structure than it could absorb."

And that would also be fantasy. It's astonishing that anyone would even try to make this claim.

[William Seger]

77. You have absolutely no idea what you are talking about.

> " It calculates how much energy the falling mass had and how much could be absorbed by the lower structure."

> No, it does not.

Utter bullshit; it does exactly that, as is perfectly clear to anyone who actually reads it and tries to understand at least the narrative if not the math. Do you really think you can bullshit your way around what's actually in that paper?

> "Bazant's calculations can be worked backwards to show that a fall of only about one foot would have put more impact energy on the lower structure than it could absorb."

> And that would also be fantasy. It's astonishing that anyone would even try to make this claim.

Well, it's not the least bit "astonishing" to claim that Bazant's calculations can be worked backwards to find the minimum fall that would produce an overload, nor is it a "fantasy" that the answer is about one foot, since those are just simple statements about the math. I assume what you mean is that your imaginary, factless, mathless physics says otherwise. The part you're leaving out, however, is any reason why a rational person should care about your imaginary, factless, mathless physics.

[OnTheOtherHand]

86. "Analysis of Inelastic Energy Dissipation" -- is that a clue?

Really, reading the section titles would seem to suffice.

It would be better, to be sure, if would-be rebutters read "we are not attempting to model the details of the real failure mechanism," and correctly inferred that they can't rebut the paper by complaining that it doesn't model the details of the real failure mechanism.

[William Seger]

89. Yup, that's a clue. The section "Elastic Dynamic Analysis" is a little less obvious, but...

... that's an analysis of how much gravitational energy had been converted to strain energy (and thus removed from the falling mass) when the columns reached their maximum elastic deformation. It shows that there was about 31 times more energy available than was necessary to push the columns through elastic deformation and into inelastic deformation, a.k.a permanent damage. If the structure had been able to absorb that excess energy by inelastic deformation, however, then the collapse would have halted at that point, so Bazant calculates that energy in the section you referenced. That analysis shows the maximum energy that could have been absorbed, best case, was only about 1/8th of the energy of the falling mass.

Anyone who wants to challenge Bazant's conclusion must do exactly one thing: Show that the structure should have been able to absorb the gravitational energy of the falling mass. The only person I know of who actually attempted to do that was Gordon Ross, and he seems to have disappeared from the "truther" scene after his "momentum transfer" analysis was shown to be fatally flawed.

[jesters]

90. ..

"It shows that there was about 31 times more energy available than was necessary to push the columns through elastic deformation and into inelastic deformation,"

No, it does not, and no there wasn't.

"Anyone who wants to challenge Bazant's conclusion must do exactly one thing: Show that the structure should have been able to absorb the gravitational energy of the falling mass."

This has already been done. First by engineers who design steel-framed highrises, second by those who point out the flaws in Bazant's analysis. Gordon Ross is one of them. Where has his analysis been shown to be flawed and by whom?

[William Seger]

122. That has NOT been done

> "It shows that there was about 31 times more energy available than was necessary to push the columns through elastic deformation and into inelastic deformation,"

> No, it does not, and no there wasn't.

That's exactly what the calculation shows, and your pretense of contradicting a leading theoretical structural engineer with nothing but naked assertion and imaginary physics would be laughable if it weren't so pathetic. Your arguments by assertion are getting tiresome. If that's all you've got, maybe you should stop and consider WHY you can't actually support any of the nonsense you're dumping all over the board.

> "Anyone who wants to challenge Bazant's conclusion must do exactly one thing: Show that the structure should have been able to absorb the gravitational energy of the falling mass."

> This has already been done. First by engineers who design steel-framed highrises, second by those who point out the flaws in Bazant's analysis. Gordon Ross is one of them. Where has his analysis been shown to be flawed and by whom?

Utter bullshit again. Nothing of the sort has been done by any qualified person, and "truthers" pretending to do so with imaginary physics and naked assertion don't even begin to count. In fact, if you know of any serious attempt besides Ross' then you really need to reference them, for a change. As for Ross, there were several minor problems with Ross' analysis that were noticed almost immediately, such as the fact that the columns were not continuous pieces of steel, and the joints every three stories would have caused some reflection of the elastic strain waves, so his strain propagation model was flawed. But the analysis lost any credibility when it was discovered that his "energy balance" had counted some energy twice: He had one line item for the energy lost in the inelastic collision and another line item for the energy required to fracture concrete. But those are the same thing: The energy lost in the inelastic collision IS the energy that breaks and deforms stuff. That's WHY it's lost, and that's the only energy available to do that work. With just that one error corrected, Ross' "energy deficiency" disappears. Some people hoped that Ross could re-do the analysis and find another "deficiency" but that entire enterprise seems to have come to an end when Bazant himself pointed out something that should have caused Ross the mechanical engineer to smack himself in the forehead at his own stupidity: A column cannot transmit more force than it takes to fail the column. It's like trying to push a car with a soda straw: No matter how much force you apply, and no matter if you do it slowly or quickly, the maximum force transmitted to the car is the force present just before the straw collapses. That meant that Ross' huge transfer of momentum through those failing columns was almost entirely imaginary, and Ross went MIA immediately thereafter.

Please don't bother responding if all you've got to say for yourself is "no it didn't." That's a pointless waste of time and bandwidth.

[jesters]

124. Some sources, please.

"With just that one error corrected, Ross' 'energy deficiency' disappears. "

I don't think so. But a source for this claim would be great. Thanks.

"Some people hoped that Ross could re-do the analysis and find another "deficiency" but that entire enterprise seems to have come to an end when Bazant himself pointed out something that should have caused Ross the mechanical engineer to smack himself in the forehead at his own stupidity: A column cannot transmit more force than it takes to fail the column. "

Who are the "some people" and in what paper did Bazant "point this out" re: Ross's analysis?

And then perhaps you can answer for us:

How the upper section has 31 times the energy that the lower section can absorb, while not assuming a free-fall initiating impact, using the correct mass value for the upper block, and calculating the energy loss in both colliding masses.

[William Seger]

155. This was discussed extensively on the JREF forum

Since I can easily predict your knee-jerk reaction to posting links to that site, I'm not much inclined to waste time digging them up -- go find it, if you're really interested. But anyway, Ross' paper itself is the only source necessary to prove that it includes both energy losses from pulverizing concrete and energy lost due to the inelastic collision, as if they were two different things. Remove that double-counting, and Ross' claimed energy deficiency disappears.

And Bazant's observation about the maximum force a column can transmit to the structure below was not a response to Ross' paper; it was part of his response to a Discussion (a letter to the editor) concerning his last paper published in the ASCE Journal of Engineering Mechanics. Since Ross apparently never made any attempt to get his paper published in a peer-reviewed journal, Bazant has never had any reason to pay any attention to it, but his observation nonetheless pulls the rug out from under Ross' momentum transfer analysis by exposing a fatal assumption.

[OnTheOtherHand]

98. yes, understanding the argument requires a bit more reading

It's pretty strange that we're not only debating Bazant and Zhou, but debating whether they offer an energy argument.

[Bolo Boffin]

74. "shown to be wrong by numerous independent analyses, on both sides of the debate."

SECOND time you've repeated this assertion. I don't care about any "shown to be wrong" from your side of the debate - show me the "numerous independent analyses" on my side.

I clearly stated what extra energy I was referring to. If the upper section is falling at 70% the acceleration rate of gravity, then the energy that would be creating the other 30% is going somewhere. Yes, it would be only available from gravity, but gravity doesn't accelerate at one rate sometimes and another rate at others. You know full well that gravity is a constant. Since the upper section is falling at an acceleration 30% slower than the acceleration of gravity, that 30% is going somewhere and doing something.

I'm asking you where and what you think that energy is doing.

[jesters]

76. 30% resistance

to a free fall acceleration is not only physically and mathematically impossible when you consider energy absorption by the columns, column deformation, pulverization of the concrete and other building contents, but you're forgetting that the upper block also could only then offer 30% resistance to the impact.

Why is it that so-called skeptics cannot see that an impact is shared equally by both colliding bodies? Why do you ignore this physical fact? How can you claim to speak for science or engineering with such nonsense?

[AZCat]

79. Please provide the proof of physical and mathematical impossibility of 30% resistance.

I prefer actual arguments, not hand-waving. Feel free to submit drawings and calculations, as these are typical methods for communicating technical arguments.

Or you could just admit your so-called impossibility is not necessarily so.

[Bolo Boffin]

80. This resistance of yours to simple requests is strange.

I've asked twice now for evidence of your assertion that independent analyses from both sides of the discussion have discredited Bazant Zhou. You've provided none. This is my third request, and if you ignore it again, I'll take from that you have no actual independent analyses from my side of the discussion and you're just asserting a falsehood.

You've also been asked for a properly labeled free body diagram, which would even help your attempt to explain to all of us "so-called skeptics" just what you mean in your description of the physics of this fall. And yet you will not do that either. I don't understand why you resist putting numbers and labels to a free body diagram.

Please provide your evidence for your "both sides discredit Bazant" assertion and a properly labeled free body diagram, if only to facilitate the discussion.

I think I've explained my objection to your theory about this pretty well. The upper section is falling, but is only accelerating at 70% of freefall. Since gravity is the only factor in this collapse and it's a constant, a large chunk of energy is being siphoned off to do something. You now say that this diverted energy is not enough to account for "energy absorption by the columns, column deformation, pulverization of the concrete and other building contents". Your calculations on that, please? And you are taking into account the fact that the upper sections in both buildings have twisted and are not hitting the structure below dead on? Pushing columns away is a lot less energy consuming than forcing them to buckle.

[jesters]

82. .

I have already explained it several times, Boloboffin, in lay terms. The calculations have been done by many others. You are now also pretending the crush-down model is actually a floor failure model, which Bazant did not talk about. So you are introducing some new hybrid theory of your own which has not been tested or proven; it's simply hypothetical. Even if they were correct, you cannot use Bazant's false energy calculations for column-on-column impact and crush-down for now a floor failure model.

The fbd you seek is provided in the OP. And here's perhaps a better explanation for you:

I would add also that you've provided no calculations of your own, merely regurgitating a ridiculous model that is easily debunked, then applying it haphazardly to some personal conjecture of your own. What exactly do you think you're doing?

[Bolo Boffin]

85. "The calculations have been done by many others." Which you continue to omit to link to.

Last edited Wed Jan 4, 2012, 11:53 AM - Edit history (1)

At this point, all I can say is either a) your assertion of Bazant debunked by both sides is false because you actually have no links to provide or b) the instant you provide these links, you know full well the ridicule the links will justly inspire. So you just keep on saying Bazant's been debunked all you like, but until you give up some links to these debunkings, we will all know you're just whistling past the graveyard.

Bazant Zhou is a energy calculation. If the lower structure can't absorb the energy, something's breaking. When the upper section has 31 times the energy than the lower section can absorb, something's definitely breaking.

"you cannot use Bazant's... energy calculations for column-on-column impact and crush-down for now a floor failure model"

The hell I can't. Column-on-column is in the building's favor. If the Bazant Zhou limiting case of column-on-column impact can't absorb the resulting energy, do you think the motherlovin' floor connections could have? And you're calling my posts ridiculous? Give me a break.

[jesters]

92. Fortunately the lower section can absorb the energy. A miracle of highrise engineering.

"If the lower structure can't absorb the energy, something's breaking."

The lower structure can absorb the energy. That's what I've been saying for the last 18 posts.

Bazant's calculations are based on an initiating free fall impact which did not occur, apparently a doubling of the mass of the upper block, and completely ignoring the energy absorption by both colliding masses.

I've listed these points now three or four times. You have yet to address them, instead merely repeating false points from a single model you're relying on that doesn't work. How about addressing these points?

"When the upper section has 31 times the energy that the lower section can absorb, something's definitely breaking. "

Explain in lay terms how the upper section has 31 times the energy that the lower section can absorb, while not assuming a free fall initiating impact and calculating the energy loss in both masses. eta: And what mass value you are using for it.

[OnTheOtherHand]

93. saying it, perhaps, but on what basis?

Where did you raise a finger to demonstrate that the lower structure can absorb the energy?

I've listed these points now three or four times.

Who cares how many times you've listed them, if you don't have any evidence for them?

[jesters]

94. Just address the points

and stop trying to reverse the burden of proof.

[OnTheOtherHand]

97. srsly?

It isn't a matter of reversing anything. Unsupported assertions are unsupported assertions; you might as well be making things up as you go. No one should have to bear the burden of proving that they actually are wrong.

[jesters]

101. Has anyone else noticed

how so-called debunkers and skeptics never answer your questions?

It almost makes you wonder if it's because they can't actually defend their bizarre theories.

[zappaman]

102. No, but I have noticed so-called "truthers" assert amazing things without evidence

Then, when asked to back up that evidence they whine that the other side doesn't answer questions.

[OnTheOtherHand]

141. I could compile a list of questions you and gyroscope haven't answered

so-called debunkers and skeptics never answer your questions

...and I could add this to the list of your unsupported claims. Quite a performance.

[Bolo Boffin]

95. "The lower structure can absorb the energy. That's what I've been saying for the last 18 posts."

Well, so much for this discussion, as far as it went. Instead of providing the things and links you've been asked for, you've taken the asinine tactics of pretending I'm the one not answering questions and stating more and more ludicrous comments like the one I quoted above.

When you decide to get serious, I'd be happy to discuss these issues with you.

P.S. Anyone interested in the ~31 figure can find the calculation in Bazant Zhou.

http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/405.pdf

It is formula number (1).

[jesters]

96. That's interesting.

You're apparently replying to my post #92, but completely ignoring my request for you to:

Explain in lay terms how the upper section has 31 times the energy that the lower section can absorb, while not assuming a free fall initiating impact and calculating the energy loss in both masses. eta: And what mass value you are using for it.

Which would actually answer most of your questions.

[Bolo Boffin]

99. Hmm. No links, no properly labeled free body diagram. Goodbye, jesters. n/t

[jesters]

103. Bye bye, Bolo Boffin.

I'll take this to mean you can't explain how the upper section has 31 times the energy that the lower section can absorb, while using an accurate estimate of the upper block's mass, not assuming a free-fall initiating impact and calculating the energy loss for both building sections in the subsequent collisions.

Kind of as I suspected.

[hack89]

104. Since the uppers section gained mass and was accelerating as it fell

I don't see the problem.

The top section didn't have to crush the entire bottom section. It only had to crush the one floor below it. It gained that mass and proceeded to crush the very next floor. Rinse and repeat 80 times.

The bottom floor had the weight of 109 floors fall on it.

[jesters]

105. Lol.

I think you should stick to the cutter charges thread.

[hack89]

107. So explain how it was not gaining mass as it fell nt

[jesters]

109. It was crushing up at the same time it was crushing down.

As per Newton's third law. (Actually, it crushed up first, but even in that event, there are some problems with how it did.)

[hack89]

113. So where did that mass go?

at the time of the collapse you had the weight of 20 floors falling. Halfway through the collapse you had the weight of 60 floors falling. Looks like a gain of mass to me.


As for Newton's third law, you do understand don't you, that the action and reaction forces don't cancel each other? That's because they are each working on different objects.

[jesters]

119. 12 floors in WTC 1

Much of the mass spilled out the sides in the form of ejecting debris.

But like I asked all of you originally, can you provide a model for a debris-driven, top-down demolition of an intact 80 - 90-storey steel framed highrise? Because no one yet has.

[hack89]

123. So the WTC did not collapse in its own footprint?

like it would in a demolition?

[jesters]

126. Can you provide a model for a debris-driven,

top-down demolition of an intact 80 - 90-storey steel framed highrise? That was the question I asked.

[hack89]

129. Sure - read the NIST report

it's all there.

[jesters]

132. Proof that you really shouldn't be in this thread.

[AZCat]

134. I don't think you want to go there.

If we're going to start acting as gatekeepers (not that I'm promoting the idea), I think a competent grasp of physics fundamentals should be nominated as a criteria.

[jesters]

138. When a poster doesn't even understand that NIST never provided

a collapse progression model, what are they doing in this thread?

As for you, if you don't want to engage this discussion in lay terms maybe you shouldn't be here either.

[AZCat]

139. That's priceless.

Now you're making excuses for your lack of understanding of physics fundamentals. It's MY fault, right?

[jesters]

140. You're right. It's too funny.

AZCAt, can you explain how WTC1's upper section had 31 times the energy that the lower section could absorb, while using an accurate estimate of the upper block's mass, not assuming a free-fall initiating impact, and factoring in the energy loss for both building sections in the subsequent collisions? Thanks.

Sorry: in plain language. Thanks.

[AZCat]

142. "In plain language."

What's your point? That any argument not dumbed-down for laypeople is not valid? Is ignorance now a defensible position?

[jesters]

143. Part of it is verifying that you know what you're talking about.

There are too many so-called 9/11 "debunkers" on the internet who pretend to expertise where they have little or none. Merely referring to a model without addressing the flaws in it does not inspire confidence.

For your part, I notice you haven't answered a single question here or made any attempt to move the discussion forward.

Knowledge of physics and its terminology is great. Use it, but it should not preclude your ability to answer questions coherently. All your replies to me so far have been in plain language. What's the problem?

The points I'm raising are widely known criticisms of Bazant's model. The question I pose here should be easy to understand. If you don't want to "dumb it down" for me, that's fine, but can you answer the question?

Can you explain how WTC1's upper section had 31 times the energy that the lower section could absorb, while using an accurate estimate of the upper block's mass, not assuming a free-fall initiating impact, and factoring in the energy loss for both building sections in the subsequent collisions?

[Bolo Boffin]

145. "widely known criticisms of Bazant's model." Links, please. n/t

[AZCat]

146. Really? I don't think I have to prove anything to you.

I've been a poster on DemocraticUnderground for far longer than you have. My posting history is extensive. I'm not going to present any other credentials, nor do I feel the need to repeat the exercise of proving myself for every new poster. I've answered plenty of questions (including a few in this thread, which you apparently haven't noticed) and have spent my fair share of time explaining basic physics. It is, however, not always worth doing so. You've displayed a poor grasp of physics fundamentals and an unwillingness to engage in productive dialog. So perhaps you'll understand (or not - I don't care either way) if I decide not to accede to your demands.

[jesters]

147. Okey doke.

But don't be presenting the Bazant model as if it doesn't have fatal flaws. Because I will bring that question back to you every time.

Same with anyone else who derides valid criticism about this ridiculous, anti-science, unworkable model.

If you're going to defend such utter b.s. then you need to answer the questions. Otherwise, don't bring it up. Isn't that fair?

[Bolo Boffin]

148. "don't be presenting the Bazant model as if it doesn't have fatal flaws" Links, please.

"valid criticism about this ridiculous, anti-science, unworkable model"

Links, please.

"such utter b.s."

Links, please.

[jesters]

149. Links?

Do you deny that Bazant assumes free fall in the initiating collapse impact? Do you deny that he has doubled the mass of the upper building portion? Can you point to where he factors in the energy dissipation on both colliding masses?

Try this one: http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/476%20WTC%20collapse.pdf

[Bolo Boffin]

150. You seem to be confused.

When asked to provide links to papers that discredit Bazant Zhou, you provided a link to Bazant Le Greening Benson which builds on the framework of Bazant Zhou. That's not discrediting it.

We keep asking you for links to papers that discredit Bazant Zhou. Personally I'm tired of listening to your assertions about it. Back them up. Present some papers, jesters. Now would be good.

[jesters]

151. I would be happy to

except that you already know about them.

And you haven't any answered any questions I've asked you -- ever.

So forget it.

The flaws I've pointed out are the common critiques of Bazant that can be readily found in any internet search. Do your own work.

[Bolo Boffin]

152. "except that you already know about them." Oh, no, you did not.

Never misrepresent me again ever, jesters.

You want to play games? Fine. But don't you dare lie about ME in your game playing. Don't you dare cite ME as pretending not to know about these false papers you keep pretending to have to back up your fantasies about Bazant Zhou.

NEVER LIE ABOUT ME AGAIN.

Got it?

Good.

[AZCat]

153. I'm with Bolo - where is the refutation of Bazant's model?

Until you provide such a document (or write it up yourself), your argument is unsupported. Any sidestepping you try to perform (like requiring we spoon feed information to you because you aren't competent to understand technical arguments) isn't going to change that.

[jesters]

156. It hardly matters, AZCat,

Since you're not even engaged in the debate.

Meanwhile, look what happens when I ask one of you to back up your claims:

http://www.democraticunderground.com/11351018#post155

[jesters]

158. From: "Not so clever Trevor"

http://gordonssite.tripod.com/id5.html

"A few people have written to me over the past few months regarding an article by Mr. Trevor Self, from Albuquerque I believe, styling himself Newton’s Bit. Rather than continue to answer these individually it will save time and effort if this reply is placed on the web and freely available. I have not previously bothered to answer this article because I did not believe that anyone would be taken in by his rubbish, riddled as it is with very basic errors, but for those who have not studied the subject it may prove beneficial to have some of these errors explained. Firstly I will deal with the arithmetical errors, then I will explain the engineering errors.

First of all the conversion from degrees to radians used by Mr Self is incorrect. There are pi (3.142) radians in 180 degrees, except apparently in New Mexico. This introduces an error of 200%.

There are four rotations in a three point buckle except in the mind of Mr Self who believes there are only three. A further error of 133%.

Mr Self uses a slenderness ratio which assumes that the columns in the towers were fitted with hinges on every storey. A casual glance at the towers proves this false, and the very fact that they stood for many years would help to confirm the non existence of these hinges. The error in slenderness ratio is 200%.

Mr Self chooses to call himself Newton’s bit for some reason but his refusal to accept Newton’s laws would have that famous man turning in his grave. Isaac Newton, or “whirling Isaac” as he is now known told us that each action has an equal and opposite reaction, but Mr Self chooses to ignore this fact conveniently allowing him to understate the energies involved by half. An error of 200%.

Mr. Self ignores the strengthening and bracing effect of the spandrel plates, core bracing, etc. The error is more difficult to quantify but is clearly significant. Why else would they have been included in the original design?

These errors when combined add up to ridiculous. It is easy to see therefore why I have previously dismissed this article without much comment. The only interesting part of this episode has been the manner in which supporters of the official story have latched onto it. There are those without the specialised knowledge to judge, who have betrayed their own unthinking bias by adopting Mr Self’s article without question. More importantly there are those who are or claim to be engineers and who do or should have that specialised knowledge and yet they have allowed the article to stand and allowed Mr. Self to continue to embarrass himself, even when these most basic errors have been pointed out.

I hope that this clears up a few issues for some people, but if questions continue then please do not hesitate to contact me."

[William Seger]

160. From Self's response

Open letter to Gordon Ross
To Mr. Ross:

I haven’t done any debunking in about a year. But imagine my surprise when I visited your website recently and found that you had finally crafted a “response” to my refutation of your “Moment Transfer in WTC1" “paper”. Please note the words that I have in quotations: response and paper. This is because I hold these items in contempt, not because they’re imaginary. I also find your lack of testicular fortitude contemptible. When in a lively internet discussion such as the one that we have had, try to have necessary courage to actually inform your opponent that you’ve said something. Otherwise it would appear (as it does now) that you’re afraid of a real response. Let’s take a look at what you’ve written and I’ll respond to it paragraph by paragraph.

If only you could investigate 911 as thorough as you investigated my name.

Quote:
A few people have written to me over the past few months regarding an article by Mr. Trevor Self, from Albuquerque I believe, styling himself Newton’s Bit. Rather than continue to answer these individually it will save time and effort if this reply is placed on the web and freely available. I have not previously bothered to answer this article because I did not believe that anyone would be taken in by his rubbish, riddled as it is with very basic errors, but for those who have not studied the subject it may prove beneficial to have some of these errors explained. Firstly I will deal with the arithmetical errors, then I will explain the engineering errors.

You’ve outed me! You have done a wonderful investigation and examined all the various clues I’ve left of myself over the internet and figured out my real name! I fear the massive unwashed hordes of Truthers hounding my every step. Or maybe I would, if I wasn’t sure that the hygiene-challenged Truthers were huddled in their parent’s basements playing the latest Halo game.

Quote:
First of all the conversion from degrees to radians used by Mr Self is incorrect. There are pi (3.142) radians in 180 degrees, except apparently in New Mexico. This introduces an error of 200%.

You got me, an arithmetic error. I intended to use 30 degree angles (pi/6) but incorrectly used 15 degrees (pi/12). Unfortunately for you, 15 degrees still falls within the bounds of my “fudging”. You see, steel columns have ruptured by 8-12 degrees anyways. Let’s just call this one a wash. I made an error, but it doesn’t matter.

Quote:
There are four rotations in a three point buckle except in the mind of Mr Self who believes there are only three. A further error of 133%.

Incorrect. This should be self-explanatory to an engineer, but I guess you didn’t have to take any Mechanics of Materials classes. Under an arbitrary amount of work, the top and bottom buckle points will rotate X degrees, however the middle one will rotate an angle of 2*X. Each buckle point absorbs the same amount of energy. Let me know if you need me to explain this further, it’s a tad bit complicated (I’m lying here: I’m trying to protect your feelings, it’s really not complicated at all).

Quote:
Mr Self uses a slenderness ratio which assumes that the columns in the towers were fitted with hinges on every storey. A casual glance at the towers proves this false, and the very fact that they stood for many years would help to confirm the non existence of these hinges. The error in slenderness ratio is 200%.

Do not put words into my mouth, HVAC designer. I never said that the tower was fitted with hinges. I can only surmise that you are making the same basic mistake that Tony Szamboti made regarding the effective length factor “K”. Please see my response to him, I’m really getting tired of having to correct this insanely basic concept of engineering. Here’s the link.

Educate yourself.

Quote:
Mr Self chooses to call himself Newton’s bit for some reason but his refusal to accept Newton’s laws would have that famous man turning in his grave. Isaac Newton, or “whirling Isaac” as he is now known told us that each action has an equal and opposite reaction, but Mr Self chooses to ignore this fact conveniently allowing him to understate the energies involved by half. An error of 200%.

Hmm. I’m not sure how my handle has anything to do with what I write. Nor do I see where this “error” occurs as my paper only deals with recalculating things you did incorrectly.

Quote:
Mr. Self ignores the strengthening and bracing effect of the spandrel plates, core bracing, etc. The error is more difficult to quantify but is clearly significant. Why else would they have been included in the original design?

The spandrel plates do not brace from buckling in a direction perpendicular to their length. They provide stiffness to in-plane forces (thus a moment frame) to deliver shear forces to the bottom of the structure. This is basic engineering mechanics. There is no excuse for not understanding this.

Quote:
These errors when combined add up to ridiculous. It is easy to see therefore why I have previously dismissed this article without much comment. The only interesting part of this episode has been the manner in which supporters of the official story have latched onto it. There are those without the specialised knowledge to judge, who have betrayed their own unthinking bias by adopting Mr Self’s article without question. More importantly there are those who are or claim to be engineers and who do or should have that specialised knowledge and yet they have allowed the article to stand and allowed


Mr. Self to continue to embarrass himself, even when these most basic errors have been pointed out.
I hope that this clears up a few issues for some people, but if questions continue then please do not hesitate to contact me.

As an aside, I have always thought that the custom on the web of allowing everyone to choose their own nickname is a little bit strange. If this were the case in real life then all the Porkys and Kiffys of this world would be calling themselves Ace or Tiger. Mr Self, or Newton’s Bit, as he appears to prefer, is a definite case in point.
You managed to find an arithmetic error (that's posted on the JREF forums) that doesn't actually change any results. You also showed how ignorant you are of structural design. Anyhoo, this has been pretty dang entertaining for me. When you have more “problems” (this quotation is both for contempt and because it’s imaginary), please actually grow a pair and let me know about them instead of hiding it on your website.

Cheers!
Trevor Self

P.S. My middle name is Newton. And my blog is my bit. Hence: Newton's Bit. Do you get it?

And of interest here is that Ross ducked out on explaining his double-counting of the concrete pulverization energy.

[jesters]

162. Probably because he doesn't do that.

I wonder if you've even read Ross's paper. You don't seem to be aware that it was Ross who points out that "the columns in the upper section could not deliver a force greater than they themselves were able to transmit."

In any case, it appears Newton's Bit's reply was not even worth a response.

From what I can tell, the main point Ross contributes here, and one that is observed by many others, is Bazant's failure to account for energy absorption and dissipation in both colliding masses. That is still true, along with the other mistakes that have been pointed out. Still fails.

[William Seger]

163. Yes, that's exactly what he does

Yes, jesters, I have read and understood Ross' analysis. You apparently have not, just as we found with the Bazant analysis.

The major item in Ross' "energy summary" loss column is "Momentum losses 1389 MJ". He got that number from these two calculations:

If we assume that the upper section comprising 16 storeys falls under a full gravitational acceleration through a height of one (removed) storey, a distance of 3.7 metres we can calculate that its velocity upon impact will be 8.52 metres per second and have a kinetic energy due to its mass and velocity of 2.105 GJ. (Using the figure of 58000 tonnes as detailed in the report by Bazant & Zhou.[1])

...

K. E. of falling sectionfiltered= 16 floors moving at (8.5 m/sec)
K. E. of falling sectionfiltered= 17 floors moving at (4.8 m/sec)
Percentage loss of K.E. = 1-(17 * 4.8/ (16 *8.5) * 100% = 66%

What Ross is doing in that last line is calculating the kinetic energy present in the masses and velocities before and after the collision, showing a loss of 66% of the kinetic energy due to the inelastic collision. So 66% of 2.105 GJ is 1389 MJ, which Ross takes as "momentum losses."

An inelastic collision is one in which the bodies deform and move off together at the same velocity. Momentum is conserved, but kinetic energy is not, because some of the kinetic energy is used to deform the bodies. Now, the specific numbers Ross used for that calculation represent his dubious notion that a huge amount of momentum was transferred to the lower structure, and his dubious low "after" velocity because of that means his calculated kinetic energy loss is dubiously high, but that doesn't matter at all here. It's only necessary to note that Ross is claiming energy losses due to the inelastic collision.

Then, in his "energy summary," Ross lists "Pulverisation of concrete on impacting floor 304 MJ" and "Pulverisation of concrete on impacted floor 304 MJ."

Does that help you to see the problem? As I said before, the kinetic energy lost in an inelastic collision IS the energy that goes into deforming and breaking stuff, including any "pulverisation" of the concrete. That's WHY the kinetic energy is lost. And importantly, because we know momentum must be conserved, we also know that's the ONLY energy available to do that work. Ross can't arbitrarily decide that the concrete is not being pulverized enough and magically direct more kinetic energy there. Furthermore, there isn't any purpose in trying to find more energy sinks like the concrete cracking, some of which Ross alludes to but does not include, because we already KNOW precisely what the total of all those losses would be -- or at least we would IF we did the momentum calculation correctly -- and Ross already showed what he's taking for that.

So, Ross counted 604 MJ of energy twice in coming up with a "Minimum Energy Deficit -390 MJ." And now he has nothing to say about it?

> In any case, it appears Newton's Bit's reply was not even worth a response.



No comment.

> From what I can tell, the main point Ross contributes here, and one that is observed by many others, is Bazant's failure to account for energy absorption and dissipation in both colliding masses.

When Ross says things like that, I can't help but think he doesn't really understand the argument. Ross claims that Bazant "assumes" that all of the energy of the falling mass was present on the impacted floor, and only there, and since that's obviously not true then Bazant's analysis must be flawed. Bullshit; Bazant "assumes" no such thing. He simply calculates how much energy would be required to fail the columns on that floor -- the floor that needs to halt the collapse if it can be halted -- and compares it to the total available. Bazant's answer is that less than 1/8th of the available energy is sufficient to lead to total collapse, even in this best-case scenario. Despite Ross' claim about Bazant's "assumption," that pretty much says to me that all of the energy does NOT need to be there! You want to include the energy that destroyed the falling floor? Fine, then there was four times more than enough to destroy both floors. You want to guess that Bazant got the mass and falling distance so wrong that his available energy was, what -- would half of Bazant's estimate make you happy? Okay, as doubtful as that is, there would still be twice as much energy available than required to fail those two floors. You want to get nit-picky and see if you can reduce it further with a host of minor details? Well, okay, but then it would only be fair to get nit-picky about such things as the fact that the fall probably involved two floors instead of one and that not all of the columns were pushed into buckling so the real collapse required less energy than Bazant's limiting case.

Contrary to your claim, despite all the nit-picking, "truthers" have so far failed to come up with VALID technical criticisms of Bazant's analysis that can quantitatively be shown to reverse Bazant's conclusion.

[jesters]

168. Here's the complete context

for those confused.

William Segar says, "Then, in his 'energy summary,' Ross lists 'Pulverisation of concrete on impacting floor 304 MJ' and 'Pulverisation of concrete on impacted floor 304 MJ.'..."

Here's what Ross wrote:

http://gordonssite.tripod.com/id1.html

"....Energy required:

Momentum losses 1389MJ

Plastic strain energy in lower impacted storey 244MJ

Plastic strain energy in upper impacted storey 215MJ

Elastic strain energy in lower storeys 64MJ

Elastic strain energy in upper storeys 126MJ

Pulverisation of concrete on impacting floor 304MJ

Pulverisation of concrete on impacted floor 304MJ

Total Energy required 2646MJ

Minimum Energy Deficit -390MJ ...."


Do you know why those items are listed twice?

Because he's accounting for Newton's third law.

[William Seger]

169. Bullshit

So far, you are the only one demonstrating any confusion.

You either didn't read what I wrote or you simply don't understand it. I'm not talking about him have two lines for "pulverisation"; I'm telling you that BOTH of those energies are NECESSARILY already included in the "Momentum losses 1389MJ" line, so he's over-counting by 608 MJ.

[jesters]

170. I see what you're saying,

but I would prefer someone who knows more about these matters to comment on why it would be included as a separate value. Considering he goes into a fair amount of detail regarding the concrete, and refers to Greening's calculations, I would guess there's a pretty good reason for it. You can certainly have momentum loss without pulverization. The fact that the concrete was pulverized does seem to warrant additional energy expenditures.

As Ross states right in his paper:

"The analysis shows that the energies expended during the time period of the plastic shortening of the first storey height of the vertical columns is sufficient to exhaust the energy of the falling section and thereby arrest collapse. ...This also shows that collapse arrest is not dependent upon an expenditure of energy in concrete pulverisation, since even if this expenditure were disregarded, the input energy would be exhausted during plastic shortening of the second storeys affected. "

Either way, you're still ignoring the fact that Ross uses both Bazant's erroneous inputs and erroneous model and still comes up with an energy deficit that he considers to be a minimum value.

[William Seger]

171. No, it seems you don't see what I'm saying

... and here's the proof:

> The fact that the concrete was pulverized does seem to warrant additional energy expenditures.

Clearly, you do not see how Ross is counting the same energy twice, but there doesn't seem to be any point in explaining it again.

And no, you have done nothing but assert over and over that Bazant uses "erroneous inputs and erroneous model" and ignored every request to substantiate that claim. After demonstrating that you don't even understand the purpose of Bazant's analysis, much less what's in it, but you're willing to blindly accept nonsense Ross put in his, even though you don't understand that one, either, I think it's clear we're not going to get anything substantive from you. So I do believe we're finished here.

[jesters]

172. You're right. I don't see it.

Because you haven't demonstrated how he's counting it twice. First you said that he made two line entries for pulverization of concrete, and that was double counting. Now it's some vague assertion that concrete pulverization would already be included in the momentum losses from the impacts through each floor, but without bothering to explain why or how, nor why an energy analysis for a building failure would automatically include concrete pulverization.

[William Seger]

173. We're finished, dude

Either you're not even reading what I write, or... well, doesn't matter.

[jesters]

174. * sniff *

The timing's just never been right for us...

[OnTheOtherHand]

175. how do you think kinetic energy is dissipated in "momentum loss"?

Go back, read post #163, and see if you can join the discussion.

First you said that he made two line entries for pulverization of concrete, and that was double counting.

Including pulverization of concrete is double counting, no matter how many line entries there are. If you're confused about that, it isn't Seger's fault.

Now it's some vague assertion that concrete pulverization would already be included in the momentum losses from the impacts through each floor, but without bothering to explain why or how,

srsly? What exactly is your problem with #163? Could it be tl;dr?

[jesters]

176. Okay I misunderstood about the double entry

But here was Seger's original statement:

"He had one line item for the energy lost in the inelastic collision and another line item for the energy required to fracture concrete."

The line item for concrete is for energy required to pulverize concrete. Pulverization and fracturing are not the same thing.


Greening seems to make a difference between fracture energy and that required to pulverize:

"...Because a single particle crushed into smaller particles exhibits a larger surface area, we need to multiply the fracture energy of 100 Joules/ m2 by the total surface area of the crushed particles to determine the minimum energy required to produce the crushed
particles. It is a minimum energy because we are neglecting any possible kinetic energy of the crushed particles in cases where particles are violently ejected from the original sample by the impact."

He also distinguishes between fracture and yield energy:

"...Ee(steel) is the elastic strain energy stored by the structural steel up to its yield point.
Ee(concrete) is the elastic strain energy stored by the concrete up to its yield point.
Ep(steel) is the plastic strain energy dissipated by buckling of the structural steel.
Ef(concrete) is the fracture energy associated with the crushing of the concrete...."

http://www.911myths.com/WTCONC1.pdf

Perhaps it's the yield energy that is found in the initial momentum loss and fracture energy needs to be accounted for on top of this.

"... As expected, the plastic strain energy dissipated by the buckling of columns (284 MJ) is confirmed to be the largest drain on the kinetic energy driving the collapse but clearly the energy to pulverize the concrete is comparable in magnitude..."

[OnTheOtherHand]

177. it isn't apparent to me that you addressed my question

Where do you think the kinetic energy in "momentum loss" goes?

Do you think that some of it might go into fracturing the concrete, but not into pulverizing the concrete?

ETA: I strongly suspect that pulverization can be characterized as extreme fracturing -- but, for the larger questions, I'm not sure it really matters whether that is true.

[jesters]

178. I don't know what Ross is factoring in to momentum loss.

However I'm pointing out to you that Greening makes a similar distinction. Can you address that point?

[William Seger]

179. Stop it, you're fracturing me

PULVERIZE. transitive verb. 1. : to reduce (as by crushing, beating, or grinding) to very small particles.

I do believe that crushing, beating, or grinding concrete reduces it to very small particles by fracturing it. If you believe something different, then yeah, I can see why you didn't understand what I was talking about.

I also believe that the initial collision fractured the concrete into pieces of all sizes, which certainly included some pulverization but surely not all of the concrete was pulverized, so I do believe Ross is the one who is being misleading by calling all of it "pulverisation" (which I keep putting in quotes because of the exaggeration, not because of the British spelling).

I also believe there was a hell of a lot of crushing, beating, and grinding going on after that collision, before that concrete hit the ground, so a guess about how much fracturing there was in the initial collision by looking at what was on the ground is not going to be very accurate. But it really doesn't matter for Ross' argument, because he already made a guess about the velocity of the mass after the collision and used that guess and the momentum conservation law to calculate a kinetic energy loss.

I was indeed wrong to say that Ross had "another line" for concrete fracturing, er, I mean "pulverisation" when there were actually two lines, but it's been a few years since I looked at it. However, the point remains that Ross can't have his cake and eat it too: either he can claim an energy loss due to the inelastic collision or he can claim energy losses for specific deformation processes, but he can't do both.

[jesters]

180. As I point out in post #176,

Greening himself makes a distinction between fracturing and pulverization, stating that pulverization does indeed require further expenditure of energy, although he uses a framework to suggest that only 10% of the concrete could have been pulverized into the fine particles, which he defines using specific measurements. Ross uses Greening's 10%, and comes up with a slightly higher energy expenditure.

Greening as well makes a further distinction for elastic strain of the concrete. So this presumably is also not factoring into the momentum loss estimates. Nor are the elastic and plastic strains for the columns. So these are all factored outside of the original momentum loss, yet you don't seem to have a problem with any of the others. Why are you picking on the concrete pulverization?

As it is explained to me, the momentum loss that Ross calculates is simply the energy expended bringing the lower mass up to the speed of the impacting mass.

[OnTheOtherHand]

181. after further review, Greening is NOT distinguishing between fracturing and pulverization

That's a relief, since I couldn't think what the distinction could be.

Above you wrote:

Greening seems to make a difference between fracture energy and that required to pulverize:

"...Because a single particle crushed into smaller particles exhibits a larger surface area, we need to multiply the fracture energy of 100 Joules/ m2 by the total surface area of the crushed particles to determine the minimum energy required to produce the crushed
particles. It is a minimum energy because we are neglecting any possible kinetic energy of the crushed particles in cases where particles are violently ejected from the original sample by the impact."

Look, he just defined "fracture energy":

In order to further quantify impact fragmentation of concrete we need to consider its fracture energy, Gf , defined as the energy needed to create a unit area of fracture surface.

He isn't distinguishing between "fracture energy and that required to pulverize."

Hell, we don't even have to refer to the definition: in the portion that you quoted, he is applying the definition of fracture energy to particles of various sizes. I submit that he introduces the concept of fracture energy because pulverization is a kind of fracturing, not because it isn't.

[jesters]

182. Your post is non-sensical.

Regardless, Greening himself sees the energy expended in fracturing or pulverizing as additional to momentum transfer. That is the main point you need to take home. Plus the point that Ross already states, that even removing those estimates still puts the energy needed for collapse propagation in deficit.

Besides, as I already asked above, why would fracture of concrete be considered part of momentum losses if column strain is not?

[OnTheOtherHand]

183. wow, tact is so wasted on you

In the passage you quoted, Greening doesn't distinguish between fracture and pulverization; he shows how fracture energy is applied to pulverization. What part of that is sailing over your head?

If you refuse to get the simple stuff right, how can you get anything else right?

I assume you know that in an elastic collision, momentum transfer occurs without any loss of kinetic energy. So I'm trying to figure out whether you have any clue what "energy expended in... momentum transfer" could possibly be. Do you?

[jesters]

185. OTOH off the deep end?

"In the passage you quoted, Greening doesn't distinguish between fracture and pulverization"

Read his paper.

"he shows how fracture energy is applied to pulverization."

He shows how to calculate energy loss for pulverization.

"What part of that is sailing over your head? "

The part where you think you have some kind of argument here but cannot articulate it, and refuse to address the points that make these nonsensical arguments irrelevant anyway.

"I assume you know that in an elastic collision, momentum transfer occurs without any loss of kinetic energy."

Why are you talking about elastic collisions?

You are making less and less sense. I don't think you've made one relevant point on this subject.

[OnTheOtherHand]

189. nope, just OTOH over your head, apparently

If you could cite a passage where Greening distinguishes between fracture and pulverization, I assume that you would. You quoted a passage about fracture energy. Fracture energy is applicable to pulverization. How could you read Greening's paper and then assert that this is not only wrong but incomprehensible?

Why are you talking about elastic collisions?

Because if you really understood the difference between elastic and inelastic collisions, you would also understand why talking about kinetic energy lost in momentum transfer is so, umm, inadequate.

[William Seger]

184. No!

As OTOH notes, you are misunderstanding Greening. There is no "distinction between fracturing and pulverization" which is exactly WHY Greening can use fracturing energy per unit area to calculate pulverization energies, by simply multiplying that fracturing energy by the surface area of the pulverized particles.

> Greening as well makes a further distinction for elastic strain of the concrete. So this presumably is also not factoring into the momentum loss estimates. Nor are the elastic and plastic strains for the columns. So these are all factored outside of the original momentum loss, yet you don't seem to have a problem with any of the others. Why are you picking on the concrete pulverization?

(Sigh.) I'm "picking on the concrete pulverization" because Ross included it in his "energy summary" even though he had already taken "momentum losses." As I have repeatedly (but futilely) pointed out to you, the kinetic energy in Ross' "momentum losses" number is ALL of the kinetic energy present before the collision but gone SOMEWHERE else after the collision. There IS no other source of energy to pulverize the concrete. A relative small amount of energy was converted to sound, vibration, and heat energy, but most of it was used in "deforming" stuff. Greening is attempting to directly calculate how much kinetic energy was dissipated by fracturing concrete, so he isn't concerned with momentum losses at all. I don't know what "distinction" you think you see, but he talks about the strain energy in the concrete only because that's where the fracturing energy really comes from: Some of the kinetic energy from the collision is converted into strain energy in the concrete and at some level of strain energy, you get fracturing.

> As it is explained to me, the momentum loss that Ross calculates is simply the energy expended bringing the lower mass up to the speed of the impacting mass.

No, the impacted mass gets velocity from direct momentum transfer. In an elastic collision, there is no kinetic energy lost and yet the impacted mass gets velocity. How could that possibly happen according to your understanding?

(Edit: OTOH types faster )

[jesters]

186. You seem to have completely ignored post #182

Why are you complaining that concrete fracturing gets a separate energy loss calculation when column strains also do? Do you think one happens in the impact and not the other?

[cpwm17]

187. I haven't really followed your complete discusion

But from looking at this link: http://forums.randi.org/showthread.php?s=ac4ce500cb601aac6743cd26bb658b3f&t=97584

I assume that the column strain energy is what is required to actually cause the structure to fail. So until the column fails, there will be no momentum transfer. So this energy doesn't contribute to the momentum of the collapse.

The energy that fractures and pulverizes the concrete before the structure hits the ground all comes from the inelastic momentum transfer. This energy is not required to collapse the building, but this energy doesn't just go away. Some of this energy will fracture and pulverize the concrete. In the calculations, there is no other source of energy to fracture the concrete.

This is my interpretation.

[William Seger]

188. You're right! Ross double-counted that energy too!

What a coincidence. I just realized that myself in looking at Greening's paper again and I just now came back here to comment on it. Greening shows an equation similar to Ross' "momentum losses" equation, then breaks down those "losses" to include all of the elastic strain energy in the steel and the concrete (which doesn't cause deformation and can be converted back to kinetic energy when the stressing force is removed), and all of the energy that buckled the steel and fractured the concrete, because it is indeed the only source for any of that energy. So you are correct; Ross screwed up even worse than I realized. Good job!

[OnTheOtherHand]

190. just to mention

I can't keep track of who posted which rebuttal of Ross when, but one reason for focusing on the energy to fracture the concrete might be that it's enough to rebut Ross's conclusion even without addressing any other problem in the paper.

I've been stuck in this loop many times on election issues. Some arguments are riddled with errors and not-even-wrongnesses. If you rebut just one, people accuse you of ignoring the rest of the argument. The further you go into the details -- which often entails conceding some whoppers for the sake of argument -- the muddier the discussion gets.

[jesters]

191. With posts 187 and 188,

the debate devolves into something like a debris-driven, top-down destruction of 80 to 90 storeys of intact steel-framed highrise. I thought I'd let you folks continue hashing it out, before I explain (again) why it's irrelevant.

Although I'm a little surprised that Seger is allowing post 188 to stand. 8-o

[OnTheOtherHand]

192. your swagger is impressive, no doubt

You've repeatedly insisted that Greening makes a distinction that he doesn't make; you've offered no explanation of where you think the kinetic energy "lost in momentum transfer" actually goes; but it doesn't seem to dampen your confidence that you know what the debate is really about.

[jesters]

193. Post 182

contains my reply to you, OTOH.

[OnTheOtherHand]

194. ROFL

You're wise to attempt to use as few words as possible.

I think your understanding of Greening's opinions on momentum transfer is on a par with your grasp of what he has to say about pulverization and fractures.

[William Seger]

195. Post 182 is bullshit

> Regardless, Greening himself sees the energy expended in fracturing or pulverizing as additional to momentum transfer. That is the main point you need to take home.

Greening EXPLICITELY shows that energy in his formula as being part of the kinetic energy lost in the inelastic collision. That EXPLICITELY contradicts the way Ross counts it as some mysterious "additional" energy. That is the main point that seems to be beyond your grasp.

> Plus the point that Ross already states, that even removing those estimates still puts the energy needed for collapse propagation in deficit.

Removing which estimates? He's showing a total of 608 MJ of energy for "pulverisation" and a "deficit" of only -390 MJ.

[jesters]

196. Are you now reversing what you said in post 188, Seger?

I don't think you've quite explained yourself on that one

[William Seger]

197. WTF are you yammering about now?

Post 188 is perfectly clear and perfectly consistent with what I just said about the bullshit in your post 182: Contrary to your assertion, Greening clearly recognizes in his formula that there was no magic energy pulled out of thin air -- the energy that did all the deforming WAS energy lost in the inelastic collision -- whereas you and Ross do not. It appears to me you're trying to bluff you way out of being caught clueless.

[jesters]

198. According to Seger's post 188,

I just debunked not only Ross, but also Seger himself, Newton's Bit, and everyone else who has analyzed Ross's paper since 2005. Apparently NO ONE has had the insight that I DID to question column strain as separate from momentum losses. I ALONE, as a COMPLETE AMATEUR, figured that out...! And William Seger had the intelligence to recognize it when I did! Wow!

[William Seger]

199. LMFAO! Have you been drinking?

But sorry; as clearly seen in the formulas they used, Newton's Bit and Greening both recognized Ross' error in counting "momentum losses" as additional to concrete and steel deformation losses, as I'm sure many people did soon after the nature of that error was noticed. I lost interest in Ross after someone pointed out the concrete pulverization thing and I hadn't given it much thought since, but the Greening paper makes it clear that the energy lost in the inelastic collision is the energy that compresses and deforms both columns and concrete slabs. Ross is absolutely debunked, no thanks to you or me, and I'm not sure where you get the delusion that you debunked anyone except yourself by refuting your own argument and not even realizing it, but thanks for the laugh. That's a classic.

[jesters]

200. No, William, you're wrong. :D

Momentum loss is not the same as kinetic energy loss. Nor does Greening try to claim this.

You stepped in a big pile of poo and you don't even know it.

[William Seger]

201. Not momentum loss; "momentum losses," Ross' term for the kinetic energy lost

Let's recap: You have repeatedly demonstrated that you don't really know what's in Bazant's, Greening's, Ross', or Newton's Bit's papers, yet you continue to make false claims about what's in them to people who do know. When confronted with what's actually in those papers, you have blithely denied it, as if you believe that reality is subjective. You have successfully resisted multiple efforts to help you understand the issues and arguments, and you appear to be completely unable to engage in any intelligent discussion of them. Instead, you continue to toss out denials and naked assertions that you refuse to even attempt to justify. In the end, you debunked your own nonsense and didn't even realize it.

Pile of poo, indeed, but I'd say I've managed to step over it.

[jesters]

203. William Seger,

your posts have displayed great inconsistencies in your own understanding. Nor have you ever "explained" anything to anyone. If anything, your posts must be deciphered through all the blather. If by some chance you do understand what you're talking about, you're utterly incapable of articulating it.

Perhaps you would like to tell the class what Ross meant by momentum losses. Ten bucks says you'll make some excuse not to.

[William Seger]

205. WTF?

It's really annoying to try to interact with someone who either doesn't even read what I write or utterly fails to understand it but then calls it "blather." I explained EXACTLY what Ross' "momentum losses" number was and how he calculated it in post #163, when you first decided to share your ignorance with us, and I'll bold the most relevant part so you can't miss it again:

The major item in Ross' "energy summary" loss column is "Momentum losses 1389 MJ". He got that number from these two calculations:

If we assume that the upper section comprising 16 storeys falls under a full gravitational acceleration through a height of one (removed) storey, a distance of 3.7 metres we can calculate that its velocity upon impact will be 8.52 metres per second and have a kinetic energy due to its mass and velocity of 2.105 GJ. (Using the figure of 58000 tonnes as detailed in the report by Bazant & Zhou.)

...

K. E. of falling sectionfiltered= 16 floors moving at (8.5 m/sec)
K. E. of falling sectionfiltered= 17 floors moving at (4.8 m/sec)
Percentage loss of K.E. = 1-(17 * 4.8/ (16 *8.5) * 100% = 66%

What Ross is doing in that last line is calculating the kinetic energy present in the masses and velocities before and after the collision, showing a loss of 66% of the kinetic energy due to the inelastic collision. So 66% of 2.105 GJ is 1389 MJ, which Ross takes as "momentum losses."

If you do not understand that simple, clear explanation of Ross' "momentum losses" then you should have bowed out of the discussion many, many posts ago. How could you possibly think that anyone would be interested in your opinions about an issue which you simply do not understand? Have you really deluded yourself into thinking nobody else understands it either, so you can just spew nonsense?

You owe me ten bucks, and I'll thank you to contribute it to DU. That would be a cheap lesson, but I have to doubt that you've really learned anything from it.

EDIT: I'll bet you another $10, also payable to DU, that you cannot find a single "inconsistency" in what I've said on this subject that isn't also a product of your own lack of understanding.

[Bolo Boffin]

202. "Momentum loss is not the same as kinetic energy loss."

I would love to hear your explanation on how these two are different.

[jesters]

204. ...kinetic energy loss through strain and fracturing. Yes.

I would love to hear your explanation on William Seger's distinction between momentum loss and momentum losses.

[Bolo Boffin]

206. That's not an explanation of the difference in your mind between

momentum loss and kinetic energy loss... or is it? Perhaps you didn't understand the question.

When explaining the difference between two things, you need to mention both, define both, and then show how one is different from the other. You didn't do that.

Feel free to try again.

[OnTheOtherHand]

207. often it would be helpful for jesters to define terms

It's true, of course, that elastic collisions preserve both momentum and kinetic energy, whereas inelastic collisions preserve momentum but not kinetic energy.

It's also true that Gordon Ross uses the phrase "momentum losses," by which he apparently means a loss of kinetic energy.

When we find ourselves trying to distinguish between "momentum loss" and "momentum losses," things are in a bad way.

[William Seger]

159. LOL, what a bullshitter

You asked for sources, and I told you precisely where I first read about the faults in Ross' analysis. I just didn't waste time digging up links for you to ignore. But let's remove that from your list of excuses for ignoring those faults, just to see what you try next:

http://bit.ly/wpqn2Z

Information overload, huh. Well, let's remove that from you list of excuses, too, and link to one extensive analysis by a structural engineer (which Ross is not) who posts on JREF:

http://newtonsbit.blogspot.com/2007/05/failure-of-truth-movements-engineer.html

So now, let's attempt once again to focus on what I claimed: There is a serious flaw in Ross' analysis that isn't easy to spot, but it's impossible to ignore once you know it's there (presuming you understand it, of course): He counts some energy twice, and correcting that removes his claimed energy deficiency. If all you can do is fart in the general direction of anyone who points it out, then that's the same as conceding the issue.

My other claim is that Ross' entire approach is undermined by the observation that a column can't transmit more force than it takes to fail the column. I believe it was Bazant who first pointed that out in the context of WTC collapses, and I told you where you could find it if you think it matters, but again it's irrelevant who first noticed that problem with Ross' analysis. The only thing that matters is whether or not Ross can still transfer enough momentum away from the collapse front to halt the collapse, given that the columns don't have the unlimited ability to do that which his analysis assumes. I admit, however, that I'm merely speculating that Ross' inability to do that is the reason he disappeared from the "truther" front several years ago -- maybe he had other reasons -- but it seems none of Gage's "architects and engineers" can do it either.

Now, please stop the games and address the issues, if you can.

(I deleted a version of this post that I edited because it ended up with a bunch of backslash characters in front of apostrophes and quote marks, and it just got worse when I tried to edit again to remove them. Seem to be a bug in the new software.)

[AZCat]

161. And that post by William Seger means?

What's interesting is that you seem to think my asking you to support your claim means you can blame your failure to do so on my refusal to play "whack-a-mole" with you. Quite amusing, too.

[Nuclear Unicorn]

154. Wait. What?

If I'm understanding correctly -- you're saying that the debris collapsing downward would have more energy than normally attributed for its mass when factoring in such variables as the engineered structural support etc. If you'll indulge my poor analogy --

It would be akin to saying a 100 pound weight dropped from a height sufficient enough to give it 250 pounds of force was dropped on a structure engineered to sustain 500 pounds of pressure, ergo the structure should not have collapsed, ergo an outside force was introduced to compel the supporting structure to collapse.

My rounded, unrealistic numbers notwithstanding, is that a fair summation of your assertion?

[hack89]

135. You are member of a tiny internet fringe group - lets not forget that simple fact

even the Birthers have more visibility than Truthers. Think about that next time you think you are a special person with special abilities to see truths that 99.9 % of your fellow citizens can't see.

Have a wonder life - you are fortunate to have a lifetime hobby.

[Bolo Boffin]

128. "intact 80 - 90-storey steel framed highrise" - just popping in to point out

The lower section was NOT an intact 80-90 story building. It was the part of a 110-story building that had just had an airplane flown into it. Part of the design of the building were the hat trusses topping off each building. The part below the impacts did not have the design benefit of the hat truss and could not in any conceivable sense be described as "intact."

Goodbye, jesters.

[jesters]

131. Bye bye, Bolo Boffin.

http://www.democraticunderground.com/11351018#post103

[AZCat]

56. I don't understand the part where you failed to support your claim.

Back upthread (post #43) you said "Secondly, and this apparently needs to be repeated across the internet: For the upper portion to EXERT THAT FORCE would REQUIRE IT TO DECELERATE. IF IT'S NOT DECELERATING, IT'S NOT EXERTING A FORCE. Because there's nothing to exert it against."

I have questioned this claim and have asked you to explain your reasoning, even suggesting you produce a free body diagram if you find it difficult to explain in words. None of your subsequent posts have done so. I would prefer we resolve this issue before moving on to your other arguments, since it appears they are at least partially based on the contended claim.

[jesters]

57. Newton's third law -- apparently deeply perplexing to 9/11 so-called debunkers

AZCat, do you know of any collisions between similar bodies that don't produce decelerations?

To drive a nail into hard wood, for example, can you rest the hammer on top of it and gently push it down? Or do you have to hit the nail? And if you have to hit the nail, what happens to the hammer? Does it continue its work in one smooth, gentle motion until it meets wood? How does it impart that force to the nail?

[AZCat]

61. Of interest to me is the second law.

That is what your claim appears to violate. Let's address that issue before moving on to your other concerns.

[jesters]

68. It would help if

It would help if you would articulate how "my" claim (Newton's third law) violates Newton's second law. If that's what you want addressed, go ahead.

[AZCat]

69. It's quite clear to me.

You stated "IF IT'S NOT DECELERATING, IT'S NOT EXERTING A FORCE." (post #43, in case you've forgotten) This is a violation of the second law. An object in a gravitation field is most certainly exerting a force on another object (or set of objects) when it is not decelerating. A simple example is an object at rest. The gravitational field exerts a force on the object, and the object exerts an equal and opposite force on the restraining system. The same is true of an object traveling at a constant velocity (i.e. not decelerating). The object must exert a force equal and opposite to that exerted on it by the gravitational field.

[jesters]

70. You took my statement as a universal.

We're talking about collisions between two bodies, as in the Bazant WTC collapse model.

[AZCat]

71. It doesn't matter what we're talking about, it's still wrong. n/t

[jesters]

72. No, it isn't.

Nor have you explained why you think it violates Newton's second law.

[AZCat]

78. Apparently you didn't read post #69.

I can't help you there - I can only post, not force you to read (or comprehend).

[jesters]

81. Lol.

The funny thing is, the fbd you're looking for is provided right in the video in the OP.

Yet you claim to not like handwaving...?

Anyone else notice how defenders of the fire n' gravity theory never actually answer the questions that naturally arise from their bizarre models?

They always, always try to turn the questioning back on you.

[William Seger]

83. What I've noticed is that post #5 is still sitting there, unanswered. (n/t)

[AZCat]

88. Well, yeah.

You didn't break it up into paragraphs. You can't expect them to read through your whole post.

[AZCat]

87. Then why didn't you say so many posts ago?

It would have saved us a lot of back and forth.

Now - looking at Chandler's FBD, can you see that the upper block is still accelerating (according to Chandler, at about 2/3G) while applying a force? This is counter to your claim that "IF IT'S NOT DECELERATING, IT'S NOT EXERTING A FORCE."

[jesters]

91. I answered this in posts 48 and 50.

You know, the ones you didn't understand?

[AZCat]

100. No, you didn't.

You sidestepped the question. Here it is again - do you still claim that "IF IT'S NOT DECELERATING, IT'S NOT EXERTING A FORCE"?

[jesters]

106. Wow.

When we're talking about collisions between two similar bodies, yes.

It is the same thing as saying that "as long as the top section of the building is in uniform downward acceleration, it cannot possibly be providing sufficient force to destroy the building.." quoted in post #26.

I notice you didn't jump all over this statement.

[AZCat]

108. It isn't the same thing at all.

You are arguing against the second law itself, while Chandler is arguing about the magnitude of the force (but acknowledges that the upper portion is still applying a force to the lower even though it isn't decelerating).

Your lack of understanding of basic physics does not bode well for a productive conversation. Perhaps you could take some time away from discussion forums to learn the fundamentals? Then we could possibly get somewhere. Until then, I don't see any point in going round-and-round with someone who says "Secondly, and this apparently needs to be repeated across the internet: For the upper portion to EXERT THAT FORCE would REQUIRE IT TO DECELERATE. IF IT'S NOT DECELERATING, IT'S NOT EXERTING A FORCE" and continues to make the claim even when challenged.

[jesters]

110. So a hammer can smoothly push a nail into hard wood, AZCat?

No impulse force is needed?

[AZCat]

111. You don't get it, do you?

No examples that you can think of will contradict the fundamental notion that an object can apply a force even if it is not "decelerating".

[jesters]

112. In two colliding bodies ?

Of the same or similar composition?

Can you provide one example? Then I can at least see why my wording might be incorrect.

[AZCat]

114. I don't know why you insist on perpetuating this argument.

The second law is pretty simple to understand. And it applies in all cases, including two colliding bodies of the same or similar composition. I think it would be quite spectacular if you could provide an example where it DIDN'T apply. Spectacular enough to possibly earn a Nobel prize.

[jesters]

117. AZCat, all it would take is one example to put me in my place

You can't do that??

I fear you perhaps don't even understand Newton's second law, let alone the third.

You have unable to articulate your objection in approximately fifteen posts.

ONE EXAMPLE of how force is applied without a deceleration in two colliding bodies of the same or similar composition.

ONE example, and I will humbly reword my original statement that is causing so many problems for you.

[AZCat]

118. No, I don't think it would do anything of the sort.

I've spent plenty of time arguing fundamental physics with people like you. Even if I provided an example, you would either move the goalposts or just dance on to the next item in your list of misunderstood topics. It's like that "whack-a-mole" game - never is there any conclusive resolution. Even if you concede on this single point, chances are pretty high I'd see it raised again (whether by you or some other poster).

What's amusing is that I've provided an example already - see post #69. An object resting on another object is the simplest example I can produce of a collision that results in no deceleration yet still has a force applied.

[jesters]

120. An object resting on another object is the simplest example

Well then my terminology is obviously incorrect. Because I wouldn't have known that an object resting on another object is considered a collision.

http://encyclopedia2.thefreedictionary.com/collision

So sticking with your unlikely and obscure technical definition, you can chalk up a physics "gotcha!" for yourself. Yay, AZCat!

So now, do you disagree with Chandler's statement that "as long as the top section of the building is in uniform downward acceleration, it cannot possibly be providing sufficient force to destroy the building." ?

[AZCat]

125. A physics "gotcha"? No, you'd have to hand that to the guy who figured it out in the first place.

Newton was a whole lot smarter than me. I just provided a simple example of the effects of his second law.

Yes, I disagree with Chandler's statement. He, however, is not arguing that "uniform downward acceleration" does not apply any force to the lower section. He is simply arguing that the magnitude of that force is insufficient to perpetuate the movement of the collapse front. He's wrong, but not as wrong as you were.

[jesters]

130. Which is what I already stated in posts 48 and 50.

We're at post 125 now.

Has anyone noticed how so-called debunkers and skeptics never answer your questions? Is it because they're unable to credibly defend the model they're relying on?

[AZCat]

133. You didn't respond to my questioning of your statement contradicting the second law.

I wanted to address that first. Considering it took us this many posts for you to acknowledge the error in your claim, I think you should probably be mindful of your own faults before claiming to see them in others.

[jesters]

136. Yeah. OR, you could have just said

"collision" in physics means other things than what you think it does.

But that would have been too quick and simple, I guess.

When you're ready to move forward the discussion, I'll engage.

[AZCat]

137. It doesn't matter if the bodies are moving or not, the second law still applies.

The example I gave is far quicker and simpler than crunching numbers on a more specific example, and I'm not sure it would be worth it.

[William Seger]

165. Again: Why Chandler is wrong

> So now, do you disagree with Chandler's statement that "as long as the top section of the building is in uniform downward acceleration, it cannot possibly be providing sufficient force to destroy the building." ?

There are three problems, actually:

1) Chandler merely assumes that the top section of the building was in uniform downward acceleration, without proof and without ever explaining how that could possibly happen even in a controlled demolition. His logic is that it can't happen in a "natural" collapse so it must have been an assisted collapse -- his desired conclusion -- thereby missing the most obvious and more likely explanation: uniform downward acceleration is just not what was really happening.

2) Local decelerations could be happening in the collapse front without being noticeable at the roof because they are very brief and the flexibility in the structure doesn't allow the deceleration to propagate all the way to the roof. Szamboti says that if that were the case, then the flexibility would also mean that not all of the kinetic energy of the top section could be applied to the lower structure in the collision because some would go into flexing the structure. That's quite true but it misses the point that we are talking about a situation where the top had much more energy than was necessary to collapse the impacted columns, so it wasn't necessary for all of the energy to be transmitted at the collision zone.

3) It IS in fact possible for the top to destroy the bottom without any deceleration, by attacking the supporting columns individually or small groups rather than all at once. This was the point about Szamboti's "missing jolt" that he refused to see: If all the columns were reacting to the collision at the same time, then yes there should be a jolt because some "load amplification" would be necessary to collapse the columns, which would be seen as a deceleration. But if the top was tilted when it impacted the floor below, then the columns would not be attacked all at once. If the effective mass bearing down on one column or small group of columns is greater than they could handle as a static load, then no "load amplification" is necessary to collapse those columns, and there would be reduced acceleration but no deceleration. It is conceivable (although unlikely) that with a tilted top, such a condition could progress across the building, sequentially collapsing columns without ever encountering enough resistance at any one time to decelerate the falling top. As unlike as that scenario is, the effect of the tilt is that any "jolts" would be much less than what Szamboti calculates by assuming all the columns resisted at once, and they could be small enough that they would be undetectable by the fairly crude method used (measuring pixel displacements in fairly low resolution videos.)

[jesters]

166. You're talking about processes,

sequential column failures which would have to happen in the time between the first detectable movement and the theoretical impact when upper meets lower. What is that time period? One second?

Or would these would have to be happening "inside" (i.e., the core columns) with nothing visible on the outside until the beginning of descent. I'm sure even you would agree this is stretching your argument beyond its credible limits.

[William Seger]

164. Example: Anything falling through air or water

A brick falling through air or water will accelerate at some rate less than g until it reaches some terminal velocity, and the entire time it will be exerting force on the air or the water to push it out of the way. There are collisions between the brick and individual molecules of air or water and energy is transferred to them, but the brick does not decelerate; the collisions just reduce the acceleration.

[jesters]

167. Sure,

but these are not comparable analogies. We are talking about two masses of the same composition. In fact, the upper block is slightly lighter in weight, smaller, and far more fire damaged than the lower.

[cpwm17]

121. Perhaps you don't understand the definition of decelerate

Decreasing the acceleration doesn't necessarily mean deceleration. It means there was a decreasing of the total forces acting on the body in the direction of motion.

In the case of an object experiencing the constant force of gravity, if another force then acts on the object in the opposite direction, the acceleration will decrease, but the body may not necessarily experience deceleration. It depends on the force applied. If the opposing force is greater than the force of gravity, then it will decelerate. Obviously not all opposing forces that can potentially act on the falling object have to be greater than the force of gravity - that would be a ridiculous claim. So your problem must be some type of misunderstanding.

[AZCat]

127. It's a pretty common misunderstanding, apparently.

I've seen similar arguments here on DU and elsewhere.

[cpwm17]

62. What happens depends on the relative forces on impact

If you drop an object it will accelerate downward due to the force of gravity. But it will also experience an opposing force trying to slow it down: air resistance. If you shoot the object downward fast enough, you can possibly give it an initial velocity above the terminal velocity such that it will decelerate until it reaches its terminal velocity. So here, as in all cases, it depends on the relative forces to determine whether an object accelerates or decelerates.

If you drop a relatively heavy object on a poorly supported small object, the heavy object will accelerate through the impact (depending on their relative masses and their abilities to withstand the impact forces). This is similar to dropped objects accelerating through the impacts with air. If you increase the size of the smaller object above some threshold, there will be a point where the large object will decelerate on impact (but only at the point of impact).

Newton's Third Law is not violated.

[gyroscope]

65. Wasn't Newton persecuted by the church?

then again, this is the Bush administration we're talking about.

the most religious anti-science nutball administration in history.

[William Seger]

84. No, he wasn't

... and the "truth movement" is just as anti-science as the Intelligent Designers. Both start with conclusions and turn the scientific method upside down trying to validate them.

[hack89]

115. Which is why we see debris falling faster than the collapse zone

there was a slight deceleration.

[AZCat]

116. Not really.

The collapse zone just has to be accelerating less than the falling debris. There is an opposing force to the collapse, but not necessarily a deceleration.

[cpwm17]

63. You're assuming the buildings had a normal ability to withstand forces after collapse initiations

Once a collapse had started, its structural integrity had been severely damaged. The buildings may have had the ability to support three times (or whatever the actual number is) their normal mass when undamaged, but certainly not after a collapse had started.

Plus during a collapse, the strongest parts of the upper and lower sections probably don't strike each other, so the resistance to collapse is minimal once started. After the top sections had mostly disintegrated, the loose rubble wouldn't just strike the strongest parts of the lower sections either.

[OnTheOtherHand]

64. also, "support" here seems equivocal

You know, static versus dynamic.

[cpwm17]

66. Yes, one could come up with more reasons why the building was guarenteed to collapse once started

- Including how rapidly the force was applied. Also the striking angles of the top sections weren't flat, so a large force was applied to a small area.

[cpwm17]

46. I didn't say they fell at free-fall speed

There was some resistance to the collapse from the strength of the structures themselves. The buildings absorbed some of the energy of the collapses. There was less resistance between the floors.

As the towers fell they collected more mass from the lower sections. This mass contributed to the collapse further down the building. But this mass collected from the lower sections started from a zero velocity, so this mass slowed down the collapse due to conservation of momentum.

For the upper portion to EXERT THAT FORCE would REQUIRE IT TO DECELERATE. IF IT'S NOT DECELERATING, IT'S NOT EXERTING A FORCE. Because there's nothing to exert it against.

The towers would only be guaranteed to decelerate if gravity disappeared during the floor collisions. Gravity is always there, and gravity is what is accelerating the towers downward in the first place. You have to analyze the relative forces to determine if the collapse decelerates or continues accelerating downward.

Dropping an object from a dozen feet (approximate distance between floors) exerts many time the force than if you just placed the object gently. The towers weren't design to support a force many times the static weight of a multi-floor section of the buildings. A complete collapse was guaranteed once it began.