CD = Free Fall?

[BasqueArch]

Hi all,

Quick question for you guys- this question came about from the WTC 7's "2.2 secs of free fall speed" concern raised by Richard Gage/Truther community at large...

Does a 'free fall' collapse automatically mean controlled demotions? In other words, can a building that has been controlled demolitioned NOT fall at free fall acceleration?

Regardless of your answer, do you have any proof that I can use for a discussion with Truthers....maybe a youtube video or other link? I looked and looked for an answer to this here but no luck.

Thanks,

-Case

For WTC1,2 the floors were 12 feet apart. The collapsing block from above encountered structural resistance every 12 feet. In between floors the top would free fall for 12 feet of air until the next floor's structure. So it's not surprising that for WTC1,2 the total collapse time was freefall + structural resistance every 12 feet, not freefall acceleration.

For WTC 7, the interior columns collapsed oh 6-8 seconds before the exterior collapsed, even slower than WTC1,2 for a total global collapse to grade. Since the interior structure had collapsed when the unsupported perimeter fell, it's not surprising the unsupported perimeter fell at freefall acceleration at that point.

2.2 seconds of freefall acceleration at the beginning = 2.2 seconds of unsurprising perimeter wall collapse whose floors supports had previously disappeared. Besides, why would Silverstein want to make a few extra bucks he didn't need and risk execution or whatever they do in NY state.

If the claim that free fall acceleration is evidence of CD, then the actual slower collapse times prove that WTC1,2,7 were not CD'd since all three fell at slower than free fall acceleration.

 

[Orphia Nay]

First, I think no answer in this thread actually halps you to answer the challenge - only to point out why the challenge is moronic.

So let me try to address the challenge.

But first, I need to ask: Did you carelessly add the word "immediate" , or is it a part of how the challenge is worded and presented?

I am asking, because the north face of WTC7 did not go into "immediate" freefall!

The true sequence is roughly this:
1. Building is already showing signs of creep for hours before the final collapse
2. Minutes before release, the roofline can be seen moving
3. Visible collapse release starts with the east penthouse falling into the core.
4. After a few seconds, the west penthouse follows
5. A fraction of a second later, the north and west face fall more or less in unison, at less than freefall, with increasing acceleration (for like 1.75 seconds, if I rememmber correctly).
6. Only after this period of increasing acceleration is freefall reached and roughly maintained for something like 2 seconds.

So there are 5 distinct phases of ongoing, progressive collapse before freefall is observed. It is easy to explain logically why freefall was possible: In particular during the 5th phase, increasing acceleration is caused by progressive loss of vertical support of the north face; in all likelihood, perimeter columns across the two faces snapped in rapid succession, till they provided no (or negligible) resistance.

Congrats to 1000 bucks

That's very good, but I suspect a bit more explanation about how this was firstly an internal collapse might be needed, focusing also on how the internal collapse caused the outer building to collapse as well.

 

[000063]

I thought the standard claim was that the buildings came down "faster than free-fall."

It's like one of those holograms; it changes depending on where you're standing when you look at it.

 

[A W Smith]

all the info you need

http://www.google.com/search?q=eule...w.,cf.osb&fp=b12f5e501efbd0e5&biw=939&bih=474

Your welcome

 

[Triterope]

In a nutshell, his challenge is this:
"I off[er] you $1,000 cash for 30 minutes of your time if you can logically explain

Newman v Schiff. Google it.

 

[alienentity]

Just had a guy show up posting this on one of my Chandler videos
http://www.youtube.com/watch?v=1rhY9c_iemA

Any comments?

'No object can have more than its gravitational potential energy

If any bit of its energy is used to crush any object or smash into this or that, it will not have a constant acceleration (greater than 0) for any significant period of time. This is the conservation of energy.

If there is any constant acceleration greater than 0 measured for any significant period of time

Pending approval
swu880 2 hours ago

His whole thesis was that ther was an outside force that persistently enacted on the wtc7 building to cause a significant time period of constant acceleration above 0

The buildin by itself sittin there can not have any more energy than its potential energy. And we know for a fact that the bottom of the building can support the top of the building. This is evidenced by well- the buildin existin prior to 9/11

swu880 2 hours ago '

 

[Grizzly Bear]

'No object can have more than its gravitational potential energy

If any bit of its energy is used to crush any object or smash into this or that, it will not have a constant acceleration (greater than 0) for any significant period of time. This is the conservation of energy.

This part doesn't really follow. You can still have an acceleration greater than zero (if you count gravity as a positive value) whilst having an opposing force provided that the net value is still "positive" when the opposing acceleration value is taken into account. I don't think the poster knows much about vector motion.

 

[Oystein]

I think the poster is missing a distinction between average acceleration of the assembly and local acceleration of each individual part at all times.

He also fails to appreciate the important concept of net forces. Energy is an important consideration, but not the only one.


Besides, hos wording isn't always fully grammatical and sensical.

If any bit of its energy is used to crush any object or smash into this or that, it will not have a constant acceleration (greater than 0) for any significant period of time. This is the conservation of energy

Unclear why he states that. If during a length of time delta-t of the fall the only force acting on the material is gravity, then acceleration is precisely 1g, and all of the potential energy is converted to kinetic energy.

If there is an upward force ("resistance"), and objects are crushed (inelastic deformation), then some of the kinetic energy gets converted to ... whaddayacallit ... fracture energy, for lack of better word (i haven't had breakfast yet ), and net acceleration will be less than 1g - how much less depends on the value of the upward force: could be >0, =0 or <0.

I think the poster is confusing something here: He read somewhere that acceleration can't be constant at 1g when energy is consumed by crashing stuff - it has to be <1g on average.

 

[Dave Rogers]

Any comments?

Let's see.

'No object can have more than its gravitational potential energy

OK so far, although it's a horribly vague form of words. In fact, it's tautological; it simply states that the gravitational potential energy of an object is not greater than the gravitational potential energy of that object. I would comment that it can't have less, either .

If any bit of its energy is used to crush any object or smash into this or that, it will not have a constant acceleration (greater than 0) for any significant period of time. This is the conservation of energy.

Rather, this is the conservation of scientifically illiterate ********. It has no basis whatsoever in any physical theory or observation. This statement, in fact, contradicts the law of conservation of energy; it implies that, if any amount of energy, however small, is subtracted from the potential energy of an object, the remaining potential energy is zero.

Your poster, quite simply, hasn't got a clue what he's talking about.

Dave

 

[sylvan8798]

Any comments?

'No object can have more than its gravitational potential energy

It seems like he could be trying to say that there are no other types of energy present, which is not technically true. For example, the structural framing (while intact) is loaded and therefore undergoing some deformation. Being elastic, once it is unloaded it will theoretically undeform. That energy is stored in the members kind of like energy in a loaded spring. While the effect during the collapse may be small, it is there nonetheless.

 

[nicepants]

In a nutshell, his challenge is this:
"I off[er] you $1,000 cash for 30 minutes of your time if you can logically explain---without the use of controlled demolition---the 2.2 seconds of gravitational free fall of WTC 7 that the National Institute of Standards and Technologies admitted to have occurred. Nothing fancy required. No calculus, no complicated formulas, just 8th-grade science class Scientific Method with the basic understanding of Newton's Laws of Motion that we started seeing in After School Special cartoons when we were five years old."

Why do I get the feeling that the goalposts will be continuously moved during those 30 minutes so as to make accomplishing this task impossible? "Nope, that wasn't logical". Then he'll start bragging about how no one could pass his challenge even for $1,000 (that he probably doesn't have anyway).

Call the bluff: Demand that the money be placed in escrow with a neutral third party (agreed upon by both) who will make the determination as to whether or not you should be awarded the money.

 

[Zeuzzz]

David Chandler (yes, THE David Chandler who, in truther speak, "forced" NIST to "admit" free-fall) has analysed a number of videos of actual explosive demolitions (those where you hear awesomely loud BANG BANG BANG BANG BANG BANGs just before collapse begins; but don't let me distract you...) and found that none exhibit free-fall.

Well that makes perfect sense doesn't it, presumably in standard controlled demolition the top section of the building still has some resistance to collapse from the building below? There will be non structural vertical supports and the fact that (depending on the particular CD) not every column is taken out, and not generally taken out 100% instantaneously (depending on the type of CD performed).

Free fall would indicate a special type of controlled demolition where for the duration of free fall the top section of the building above the damaged area encounters practically no resistance to its downwards acceleration of -9.81 m/s. The evidence shows that the gradient of the v/t graph is constant for the first ~2.5 seconds of collapse. That is to say that even if for the first 2.5 seconds of the collapse the top section of the building was in fact falling through thin air it would be falling at the same rate we see it falling on top of the steel structure below.

Since GPE is simply being converted to E_k in the collapse then basic Newtonian mechanics shows that any resistance will be shown as a reactionary deceleration of the ~9.8 value.

This is puzzling (to me) as the onset of the collapse should be the part of the collapse with the most resistance and thus have a much smaller acceleration compared to the rest of the collapse, as a lot of the supports at the initiation floors will be not be damaged enough to provide no resistance at all. Thus the value of acceleration at the beginning of the collapse should be less than at later stages of the collapse as it progresses.

Instead it starts off at the very maximum level of a and then only starts to decelerate much later.

 

[Oystein]

Well that makes perfect sense doesn't it, presumably in standard controlled demolition the top section of the building still has some resistance to collapse from the building below? There will be non structural vertical supports and the fact that (depending on the particular CD) not every column is taken out, and not generally taken out 100% instantaneously (depending on the type of CD performed).

I wouldn't go so far with my speculation.
Chandler's observation merely negates the AE911T claim that free fall is a characteristic of CD.

Free fall would indicate a special type of controlled demolition

Why special type of controlled demolition and not, for example, special type of natural collapse?

where for the duration of free fall the top section of the building above the damaged area encounters practically no resistance to its downwards acceleration of -9.81 m/s.

Well, pedantic as some are around here, that would be net resistance, but okay.

The evidence shows that the gradient of the v/t graph is constant for the first ~2.5 seconds of collapse. That is to say that even if for the first 2.5 seconds of the collapse the top section of the building was in fact falling through thin air it would be falling at the same rate we see it falling on top of the steel structure below.

No, this is FALSE.
The evidence shows that acceleration of the top gradually increases from 0 to close to g during the first x^(*) seconds of the collapse, which is slower than it would have fallen through thin air.

Since GPE is simply being converted to E_k in the collapse then basic Newtonian mechanics shows that any resistance will be shown as a reactionary deceleration of the ~9.8 value.

This is puzzling (to me) as the onset of the collapse should be the part of the collapse with the most resistance and thus have a much smaller acceleration compared to the rest of the collapse, as a lot of the supports at the initiation floors will be not be significantly damaged.

But this is what we see: Initially, acceleration is closer to 0 than to g, which means some of the GPE gets converted into buckling structural elements. This goes on for x^(*) seconds before free-fall is attained. By then, apparently perimeter columns across the north face have completely buckled around the 8th floor.

Thus the value of acceleration at the beginning of the collapse should be less than at later stages of the collapse.

And it is

Instead it starts off at the very maximum level and then only starts to decelerate much later.

No. Please revisit NIST's, Chandler's or femr2's tracing of the north wal decent and find that it does not begin at a=g.



^(*) I do not know at this time the value of x. Something like 1.75 seconds? 1 second? Too lazy to look it up. At any rate, g was reached only some time after the roofline started to decent.

 

[GlennB]

Free fall would indicate a special type of controlled demolition where for the duration of free fall the top section of the building above the damaged area encounters practically no resistance to its downwards acceleration of -9.81 m/s. The evidence shows that the gradient of the v/t graph is constant for the first ~2.5 seconds of collapse. That is to say that even if for the first 2.5 seconds of the collapse the top section of the building was in fact falling through thin air it would be falling at the same rate we see it falling on top of the steel structure below.

Since GPE is simply being converted to E_k in the collapse then basic Newtonian mechanics shows that any resistance will be shown as a reactionary deceleration of the ~9.8 value.

This is puzzling (to me) as the onset of the collapse should be the part of the collapse with the most resistance and thus have a much smaller acceleration compared to the rest of the collapse, as a lot of the supports at the initiation floors will be not be damaged enough to provide no resistance at all. Thus the value of acceleration at the beginning of the collapse should be less than at later stages of the collapse as it progresses.

Instead it starts off at the very maximum level of a and then only starts to decelerate much later.

Do yourself a favour. Read Oystein's reply to this post.

 

[Zeuzzz]

Why special type of controlled demolition and not, for example, special type of natural collapse?

A special type of natural collapse would seem far more unlikely, purely as in a CD you know that most of the support is being taken out intentionally, and the support of the other parts of the building will be taken out by the weight of the falling section. To assume that nearly all of the supports fail, nearly simultaneously, by a natural collapse seems much more unlikely as these are the same supports that have been keeping that building standing for years. To fail so catastrophically implies an extremely major design fault, in every one of the major supports, that should be extremely obvious to point out in the buildings designs.

No, this is FALSE.
The evidence shows that acceleration of the top gradually increases from 0 to close to g during the first x^(*) seconds of the collapse, which is slower than it would have fallen through thin air.

Interesting, I'd like to know the value of x^*. The smaller the more suspicious still but i'm prepared to accept that could be true.

But this is what we see: Initially, acceleration is closer to 0 than to g

Well if true the v/t graph might not be missing the beginning portion I thought it was then, that's the impression I got from watching Chandlers video.

 

[Miragememories]

"Free fall would indicate a special type of controlled demolition where for the duration of free fall the top section of the building above the damaged area encounters practically no resistance to its downwards acceleration of -9.81 m/s. The evidence shows that the gradient of the v/t graph is constant for the first ~2.5 seconds of collapse. That is to say that even if for the first 2.5 seconds of the collapse the top section of the building was in fact falling through thin air it would be falling at the same rate we see it falling on top of the steel structure below."

"Why special type of controlled demolition and not, for example, special type of natural collapse?"

A special type of natural collapse?

"Special" seems like a contradiction to natural?

natural = "occurring as a matter of course and without debate; inevitable"

special = "different from what is usual"

So you are suggesting that the collapse of WTC7 was a "an unusual type of inevitable collapse"?

Interesting.

MM

 

[GlennB]

Well if true the v/t graph might not be missing the beginning portion I thought it was then, that's the impression I got from watching Chandlers video.

The graphs showing acceleration v. time are the important bit, not watching videos.

The classic CD theory requires instant removal of all support leading to freefall. So why should there be period of < g collapse before that? Was the building getting a bit creaky and feeble just before CD kicked in?

 

[alienentity]

To assume that nearly all of the supports fail, nearly simultaneously, by a natural collapse seems much more unlikely as these are the same supports that have been keeping that building standing for years. To fail so catastrophically implies an extremely major design fault, in every one of the major supports, that should be extremely obvious to point out in the buildings designs.

Well, that's the thing: Only truthers make the assumption that all the supports fail simultaneously, because they clearly don't!
Since you already had the partial destruction of the building for several seconds prior to the exterior columns buckling, these assumptions are incorrect.

Furthermore, 9/11 conspiracists require, doctrinally, that ALL the exterior columns were blown with cutter charges simultaneously. Yet this clearly did not happen! There is NO evidence of cutter charges, as required, on the exterior columns - not on video, still photographs, eyewitness accounts or on the steel columns examined and sorted at Freshkills.

This theory is a massive failure on many levels. I think it's a natural collapse due to flawed reasoning, but some might call it a controlled demolition, an inside job - which destroys 9/11 conspiracy theories.
(if so, WHO is trying to destroy 9/11 Truth from the inside, and WHY? )

 

[Oystein]

A special type of natural collapse would seem far more unlikely, purely as in a CD you know that most of the support is being taken out intentionally, and the support of the other parts of the building will be taken out by the weight of the falling section.

And you base this assessment on what? Personal imagination? Intuition?

To assume that nearly all of the supports fail, nearly simultaneously, by a natural collapse seems much more unlikely as these are the same supports that have been keeping that building standing for years.

Well, they didn't all fail nearly simultaneously, so that problem is taken care of
Ok, but these supports were designed to hold up an intact building. But as you probably know, collapse of the building core was already ongoing for for several (on the order 5-6) seconds before the north wall roof started to decent. Once columns start to fail, load distribution happens at the speed of sond in steel, and it isn't really all that surprising if collapse propagates quite rapidly.

To fail so catastrophically implies an extremely major design fault, in every one of the major supports, that should be extremely obvious to point out in the buildings designs.

You base this assessment on what - your thorough education as a structural engineer? Years of experience investigating strutural failures? Your layman's intuition?

Interesting, I'd like to know the value of x^*. The smaller the more suspicious still but i'm prepared to accept that could be true.


Well if true the v/t graph might not be missing the beginning portion I thought it was then, that's the impression I got from watching Chandlers video.

Hm I suggest you find and show that graph here, so we can all see what we are talking about. Okay?

 

[Zeuzzz]

Well, that's the thing: Only truthers make the assumption that all the supports fail simultaneously, because they clearly don't!

Please note that I said nearly simultaneously.

Since you already had the partial destruction of the building for several seconds prior to the exterior columns buckling, these assumptions are incorrect.

What do you mean by "partial destruction of the building for several seconds"

The fact that some columns may have been damaged prior to collapse initiation I cant see making a whole lot of difference, unless somehow the majority of the main core columns happen to have failed in an extremely similar way.

Furthermore, 9/11 conspiracists require, doctrinally, that ALL the exterior columns were blown with cutter charges simultaneously. Yet this clearly did not happen! There is NO evidence of cutter charges, as required, on the exterior columns - not on video, still photographs, eyewitness accounts or on the steel columns examined and sorted at Freshkills.

I never mentioned cutter charges.

I think it's a natural collapse due to flawed reasoning

So do many people round here.