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Getting back to the free fall acceleration, NIST said that the upper portion of the building moved down as a single unit at that the acceleration was 9.81 m/s2, equivalent to the acceleration of gravity. This is within 1/10 of 1% of the acceleration of gravity for New York City which is 9.802 m/s2 and that is as close as a measurement can be [actually minutely faster than FF]. The resistance from the supporting structure was as "negligible"[too small to be considered] as the air. There was NO measurable resistance.
As Shyam Sunder rightly said "a free fall time would be an object that has no structural components below it. . . . there was structural resistance that was provided in this particular case. And you had a sequence of structural failures that had to take place. Everything was not instantaneous."
In other words, the NIST progressive collapse hypothesis does not include a period of free fall acceleration because there is always structural resistance.
Maybe it was being pulled down by the inside. It depends if they blew up the core columns before detonating the perimeter columns. There would be some dynamic energy causing it to collapse fast, perhaps at g if the core columns were blown first.
For the rest of the towers you can generally see debris falling faster than the tower collapsing. But perhaps when the explosives went off that they pushed some of the debris down so that it is falling faster than g. Or it could be that they missed-time the explosives on every floor so that the columns gave some resistance.
It all leads to explosions doesn't it.? But perhaps there is a more obvious explanation and perhaps we should ask an engineer.
Maybe it was being pulled down by the inside. It depends if they blew up the inside columns before detonating the outside columns. There would be some dynamic energy causing it to collapse fast, perhaps at g.
For the rest of the towers you can generally see debris falling faster than the tower collapsing. But perhaps when the explosives went off that they pushed some of the debris down so that it is falling faster than g. Or it could be that they missed-time the explosives on every floor so that the columns gave some resistance.
It all leads to explosions doesn't it.? But perhaps there is a more obvious explanation and perhaps we should ask an engineer.
Jones found "nano-thermite", missed the nanobots eating the steel. I measured the video collapse, parts fell faster than free-fall. 911 truth is ... (undefined stupid)
Chris, I may be in the minority on this forum when I agree with you that free-fall means no structural resistance. Maddening though it is to spend time on 8 out of 47 floors in free-fall, I'm going through the exercise. So let's say you're right when you say " the NIST progressive collapse hypothesis does not include a period of free fall acceleration because there is always structural resistance."
I've disagreed with NIST before, and their explanation that "gravity takes care of it" was not enough for my mind. Ryan Mackey's explanation made a lot of sense to me. He shows how, for the short time of freefall, there can indeed be no resistance: At least One 8-story chunk of floors held onto the perimeter wall. We see an eight-story buckle, due to the eccentric loading in the corner. Those floors attached to the perimeter after the core fails literally pulls in eight stories of column.
And I wonder: could this yanking down have caused the building to collapse at slightly greater than free fall due to torquing, or is the "faster than freefall" simply a computational thing where the acceleration was so close it just measured a tiny bit faster without actually being faster?
Chris, I may be in the minority on this forum when I agree with you that free-fall means no structural resistance. Maddening though it is to spend time on 8 out of 47 floors in free-fall, I'm going through the exercise. So let's say you're right when you say " the NIST progressive collapse hypothesis does not include a period of free fall acceleration because there is always structural resistance."
I've disagreed with NIST before, and their explanation that "gravity takes care of it" was not enough for my mind. Ryan Mackey's explanation made a lot of sense to me. He shows how, for the short time of freefall, there can indeed be no resistance: At least One 8-story chunk of floors held onto the perimeter wall. We see an eight-story buckle, due to the eccentric loading in the corner. Those floors attached to the perimeter after the core fails literally pulls in eight stories of column.
And I wonder: could this yanking down have caused the building to collapse at slightly greater than free fall due to torquing, or is the "faster than freefall" simply a computational thing where the acceleration was so close it just measured a tiny bit faster without actually being faster?
The 21 core columns under the screenwall and west penthouse failed east to west in about 1 second as can be seen in the videos. The loads they carried were transferred to the exterior columns causing them to buckle in an irregular manner, which precludes their all failing at the same time. When 7 floors of the remaining 52 exterior columns were removed, the core columns which were already moving, may have momentarily increased the free fall acceleration of the exterior columns that were just going into free fall acceleration thus giving a slightly faster than free fall time for the 2.25 seconds. However, it is also possible that the discrepancy is due to the fact that they were looking at pixels which is very accurate but not perfectly accurate. In any case the 8/100ths of a second is negligible. [too small to be considered]
We are left with no measurable resistance for about 100 feet and that can only occur if there are no structural components below and that can only occur if all the supporting structure on 7 floors is removed in a synchronistic fashion within the 2.25 seconds.
I appreciate your honesty. I have noticed that very few people on either side of the debate are willing to admit that they are wrong. My philosophy is: I may not always be right but I'm never wrong for long. When faced with facts or sound logic that proves my position incorrect, I immediately change my position to fit the new data.
This is completely, hopelessly false, yet you say it with such confidence.
"...Thomas Cahill, a UC Davis professor emeritus of physics and atmospheric science and research professor in engineering..."
Is quoted in this LINK as saying:
"The debris pile acted like a chemical factory. It cooked together the components of the buildings and their contents, including enormous numbers of computers, and gave off gases of toxic metals, acids and organics for at least six weeks."
In their paper, Analysis of Aerosols from the World Trade Center Collapse Site, New York, October 2 to October 30, 2001, Cahill reports...
"we recorded the highest levels [of all classes of polutants] we have ever seen in over 7,000 measurements we have made of very fine air pollution throughout the world, including Kuwait and China,".
Chris, I may be in the minority on this forum when I agree with you that free-fall means no structural resistance. Maddening though it is to spend time on 8 out of 47 floors in free-fall, I'm going through the exercise. So let's say you're right when you say " the NIST progressive collapse hypothesis does not include a period of free fall acceleration because there is always structural resistance."
I've disagreed with NIST before, and their explanation that "gravity takes care of it" was not enough for my mind. Ryan Mackey's explanation made a lot of sense to me. He shows how, for the short time of freefall, there can indeed be no resistance:1 At least One 8-story chunk of floors held onto the perimeter wall. We see an eight-story buckle, due to the eccentric loading in the corner. Those floors attached to the perimeter after the core fails literally pulls in eight stories of column.2
And I wonder: could this yanking down have caused the building to collapse at slightly greater than free fall due to torquing,3 or is the "faster than freefall" simply a computational thing where the acceleration was so close it just measured a tiny bit faster without actually being faster?
Chris. You have three of the key elements there see my indexing as 1,2 & 3. Let me try to put across some of the frustrations that we structural engineers feel trying to explain why free fall of part of a collapsing structure is not an issue of concern to us. (That is of no concern other than when it comes to convincing lay persons who have doubts.
)
The overriding problem is that the truth movement has done a pretty good job selling the false meme that free fall == demolition AND they don't even debate it - simply take it as given in their posts/presentation. Sound propaganda technique I suppose. I think that you are now fully aware of that one.
Now next below that is their use of presumed or implied global settings. By that I mean the technique of presenting claims for free fall as if they applied to the whole structure and that the structure acted in a homogeneous way. That one also rarely stated and quite often only partially relied on. It appears to be implicit in your agreement with Chris7 where you say: "...when I agree with you that free-fall means no structural resistance..." There are two problems in that statement.
First is the presumed global application which you may or may not intend. I would prefer the statement if it said this: "...when I agree with you that free-fall means no structural resistance to the free fall of the specific element of structure we are considering..."
That partially resolves the problem with the statement as it originally stood. But it is not only "no resistance" we need to consider. That "no resistance" is usually set in a context which presumes no support because no connection whatsoever. It is used that way by most truthers and sadly by debunkers responding with less than full rigour in their comments.
Second is the reality that free fall acceleration occurs when there is zero net resistance. Ryan has identified and you have recognised that there could be "pull down". The free fall could in fact exceed g for part of an element or a subset of elements which were subject to pull down. Leveraged pull down is simplest illustrated by this clip which you may have already seen. http://www.youtube.com/watch?v=BV7TPvk__kE
And those complications apply to what is already a complex collapse scenario where we cannot know now and never could know with surety which bits did what to which other bits. So we have:
The possibility of bits falling at free fall for reasons of no resistance due to no connected structure.
The possibility of some bits falling faster than free fall due to leveraged pull down. AND
The possibility of leveraged pull down or other mechanisms exactly balancing the gravitational effect and resulting in net zero "resistance".
All three of those are possibles and even probables given the complexity of the overall collapse.
Hence the frustration of those of us who can with confidence not worry about proving free fall because our professional training supports the reasoning. But there is no simple way to pass that confidence to genuine enquirers like yourself. And it is still at least one big quantum leap away from giving you arguments to persuade those who do not want to be persuaded.
So your comment "...could this yanking down have caused the building to collapse at slightly greater than free fall due to torquing,..." I have no doubt that it could - whether or not it did I cannot comment. However another member here, femr2, specialises in measurements from video analysis and I understand that he has measured some aspects of the fall and found greater than free fall accelerations. I cannot recall the thread.
The 21 core columns under the screenwall and west penthouse failed east to west in about 1 second as can be seen in the videos. The loads they carried were transferred to the exterior columns causing them to buckle in an irregular manner, which precludes their all failing at the same time. When 7 floors of the remaining 52 exterior columns were removed, the core columns which were already moving, may have momentarily increased the free fall acceleration of the exterior columns that were just going into free fall acceleration thus giving a slightly faster than free fall time for the 2.25 seconds. However, it is also possible that the discrepancy is due to the fact that they were looking at pixels which is very accurate but not perfectly accurate. In any case the 8/100ths of a second is negligible. [too small to be considered]
We are left with no measurable resistance for about 100 feet and that can only occur if there are no structural components below and that can only occur if all the supporting structure on 7 floors is removed in a synchronistic fashion within the 2.25 seconds.
I appreciate your honesty. I have noticed that very few people on either side of the debate are willing to admit that they are wrong. My philosophy is: I may not always be right but I'm never wrong for long. When faced with facts or sound logic that proves my position incorrect, I immediately change my position to fit the new data.
In the current thread "Chandler and constant speed"
Eric C
Edit PS femr2 has been regular here in recent months - together with two colleagues. All three are seen as "truthers" by many members here. I make no judgement on that. They are regulars also on http://the911forum.freeforums.org/scientific-and-technical-forums-f36.html which is seen as truther friendly - again I make no judgement. That forum has a fair bit of detailed technical discussion and free of the high noise of "truther v debunker" polarisation. I am not a member there fwatitswurth.
You had previously stated that free fall acceleration is not unexpected or words to that effect.
There was a period of free fall acceleration that lasted for about 100 feet and that means that all the supporting structure on 7 or 8 floors was removed in a synchronized manner, that is; all the supports on each floor were removed simultaneously in order for the entire upper portion of the building to fall straight down as a single unit as is noted on page 45 of the final report.
The comparison of Figure 12-63 showing the buckling columns which provide resistance, and below is the same graphic with the columns removed as is required for FFA, begs the question - What removed them? http://img851.imageshack.us/img851/1647/bucklingvnothing.jpg
The columns could be removed in a synchronistic manner with the use of explosives or a combination of incendiaries and explosives but not in a progressive collapse.
True but there is no evidence to suggest such use, arguably no strategic valid reason for anyone (either "side" - Terrorists OR GW Bush conspirators) to use same; AND well nigh impossible - enough to satisfy me- that there could not have been any demolition assistance. I am military engineer qualified and my approach to WTC collapses has been strongly influenced by "How would I do it if the General gave me the task?" I couldn't do it without leaving evidence and getting caught.
..as an engineer I cannot accept this global claim. There are many potential mechanisms, some which I could possibly suggest, many more that are beyond my ability to reasonably predict given the paucity of direct and relevant information.
My personal "bottom line" for the two critical anti-demolition stages of WTC 9/11 collapse (those are the collapse initiation for WTC1 and WTC2 and the equivalent stage for WTC7) is that I, on the publicly available evidence cannot technically prove "no demolition". However the strategic - or "why do it" arguments plus the stronger "it could not be achieved without discovery" AND "it was ridiculously close to impossible" arguments carry the day for me. That is "no demolition".
For WTC Twin Towers the only "viable" demolition without discovery scenario required charges placed in the middle of the fire zone by fire proof suited suicide squads. Not likely by my summation. When WTC7 became the priority discussion event I saw it as the "truth movement" grasping a straw because the evidence against demolition was not readily and visibly available as it is with the twin towers. So the cynic in me doesn't debate WTC7.
...
There was a period of free fall acceleration that lasted for about 100 feet and that means that all the supporting structure on 7 or 8 floors was removed in a synchronized manner, that is; all the supports on each floor were removed simultaneously in order for the entire upper portion of the building to fall straight down as a single unit as is noted on page 45 of the final report.
...
The columns could be removed in a synchronistic manner with the use of explosives or a combination of incendiaries and explosives but not in a progressive collapse.
I would like to disagree. Acceleration increased during the 1.75 (or so) seconds leading up to the free-fall phase. There wasn't much of a discontinuity in the a values there, which means support wasn't removed simultaneusly but rather over a (short) period of time. Free fall simply means that all support was removed by then, and not necessarily exactly then.
However,. if you have a period during which supports fail, then we are talking progressive collapse. Remember, load redistribution happens at the speed of sound.
We have agreed that WTC 7 fell at free fall acceleration for about 100 feet and that Shyam Sunder has rightly stated that means there was no supporting structure below the falling upper portion of the building.
C7 said:
The columns could be removed in a synchronistic manner with the use of explosives or a combination of incendiaries and explosives
but there is no evidence to suggest such use, arguably no strategic valid reason for anyone (either "side" - Terrorists OR GW Bush conspirators) to use same; AND well nigh impossible - enough to satisfy me- that there could not have been any demolition assistance. I am military engineer qualified and my approach to WTC collapses has been strongly influenced by "How would I do it if the General gave me the task?" I couldn't do it without leaving evidence and getting caught. ..as an engineer I cannot accept this global claim.
So your position is: "I could have not done it without leaving evidence so therefore it cannot be done." That is because you are not thinking "outside the box". Have you seen this video by Jon Cole? He invented a device that cuts columns using regular thermite. http://www.youtube.com/watch?v=5d5iIoCiI8g&feature=related
People have been claiming that it could not be done because they have no imagination and will not accept that the military has demolition devices and techniques that we don't know about. The main point Jon makes is that just because the public doesn't know all that is possible doesn't mean it isn't possible.
There are many potential mechanisms, some which I could possibly suggest, many more that are beyond my ability to reasonably predict given the paucity of direct and relevant information.
The only known mechanism that can remove all the supporting columns in a synchronistic manner that will allow for implosion is some form of explosives. Implosion is a fine art and could not happen as the result of the failure of a single column or demolitions companies would not go to all the trouble of rigging most or all the support columns.
My personal "bottom line" for the two critical anti-demolition stages of WTC 9/11 collapse (those are the collapse initiation for WTC1 and WTC2 and the equivalent stage for WTC7) is that I, on the publicly available evidence cannot technically prove "no demolition". However the strategic - or "why do it" arguments plus the stronger "it could not be achieved without discovery" AND "it was ridiculously close to impossible" arguments carry the day for me. That is "no demolition".
"It can't be because . . . ." is a denial position and requires ignoring the reality that the only explanation for building 7 imploding and/or falling at free fall acceleration is removing all the supporting structure on 7 to 8 floors in a controlled sequence using some kind of explosive and/or incendiary device.
Sorry Chris,
I thought you were talking about WTC1 and 2
WTC 1 & WTC 2
Clearly the bombs in WTC 1 and 2 were carefully placed at the impact zone. And must have been well insulated to prevent the fire from interfering with the detonators. Since it was a quiet flashless explosion it must have been thermite, but there was some steel blanketting or some protective screen on the perimeter columns so that the flashes would not be seen.
The thermite bombs were combined with a few ordinary bombs that would go of during the collapse to enable steel to be hurled 500ft. The collapse noise covering up the explosions.
On WTC 1 they blew up the inner columns first and then had a set of super-fast thermite bombs at every level to give nominal resistance and nearly free-fall.
While on WTC 2 they decided to blow up the perimeter columns first followed by a series of super fast thermite bombs to give a nearly free fall.
And much of the thermite failed to explode, about 160 tons, according to our calculations at ae911truth. That must have been the main ignition material that they placed at all levels just in case the plane hit at some other level.
WTC 7
WTC 7 was not quite as obvious. But they certainly blew up the inner columns before the outer ones. We know that from the collapsed penthouse.
I guess they then used flashless hidden thermite bombs on all the perimeter structure. I think that was only 80 columns. And they exploded them at every level for over 100 ft to provide no resistance so that we got free-fall speed.
The government then supervised the debris removal so that there was no evidence of this and no-one saw anything suspicious. That's why we need subpoenas so that we can find out what they are not telling.
The only known mechanism that can remove all the supporting columns in a synchronistic manner that will allow for implosion is some form of explosives. Implosion is a fine art and could not happen as the result of the failure of a single column or demolitions companies would not go to all the trouble of rigging most or all the support columns.
A patently false statement and an equally false conclusion regarding demolition companies.
"It can't be because . . . ." is a denial position and requires ignoring the reality that the only explanation for building 7 imploding and/or falling at free fall acceleration is removing all the supporting structure on 7 to 8 floors in a controlled sequence using some kind of explosive and/or incendiary device.
We have agreed that WTC 7 fell at free fall acceleration for about 100 feet and that Shyam Sunder has rightly stated that means there was no supporting structure below the falling upper portion of the building.
Not necessarily. If the load is many times greater than the load that the structure below is able to resist, the acceleration of the collapse can be very close to the acceleration of gravity.
The only known mechanism that can remove all the supporting columns in a synchronistic manner that will allow for implosion is some form of explosives.
Implosion is a fine art and could not happen as the result of the failure of a single column or demolitions companies would not go to all the trouble of rigging most or all the support columns.
Are you saying "progressive collapse" doesn't exist?
The art of implosion is not only to bring down buildings, but also make it so that there is no risk of damage to the buildings nearby. That's why demolition companies put explosives in multiple columns of multiple floors.
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