Why a one-way Crush down is not possible

[AndrewIlluminatus]

On the one hand we have your bare assertion, unsupported by any attempt at calculations, that there was not enough potential energy in the Twin Towers to produce the observable effects. On the other we have the painstaking and thorough calculations by Frank Greening, Gregory Urich, Newtons Bit and others - I've even reproduced them myself and reached the same conclusion - which demonstrate mathematically that there was ample potential energy to produce these effects. Oh, the dilemma - should I believe you, or my own lying maths?

Dave

Although the exact time of the collapse of WTC 1 and 2 cannot be determined with precision because of the growing dust cloud, each collapse took approximately 10-12 seconds. NIST NCSTAR "Within 12s, the collapse of WTC1 had left nothing but rubble." Only 2 seconds slower than the time for a reasonably dense object that was not overly influenced by air buoyancy at 1.2kg/cubic metre (and air drag), to fall from the WTC roof to the plaza. Therefore, air resistance alone will make it take longer than 10 seconds for gravity to pull an object to the ground from the former height of WTC1 or 2 (time would be about 9.2 seconds in a vacuum). That 12s represents extraordinarily insufficient resistance within the intact tower structure to have permitted the kind of impacts imagined to produce sequential kinetic energy impacts and kinetic energy explosions in a ripple down manner. The energy from gravity has to be used up and it cannot be expected to do two jobs at once. Either all the energy from gravity is used up to create imagined tonnes of TNT kinetic energy explosiveness in sequential one-off explosive ripple-down events or it is used up to get an already explosively disassembled (by other means) building to the ground in that sort of time frame.

Additionally it is clear from video of the WTC2 event that the top load tipped over to the East, so did not apply a symmetrical weight load to the tower below yet within about 2 seconds of the explosive collapse initiation, the top load was explosively disassembled in mid-air upwards. Moreover for the initial symmetrical explosive collapse process below the tipped over top, during the first few seconds the ripple down, explosive blow outs shot down the tower faster than the explosively ejected building material from the top could keep up. This means that in the initial stage of the "WTC2 collapse process" the symmetrical-ripple-down-explosiveness, purportedly from a top load exerting an asymmetrical weight load, since it had tipped over before it was explosively disassembled upwards, was faster than the time for a reasonably dense object to fall through air.

On page 305 of the 9/11 Commission Report, we are told, in the government's "complete and final report" of 9/11 that the South Tower collapsed in 10 seconds. Here is the exact quote: "At 9:58:59, the South Tower collapsed in ten seconds". Actually that is probably slightly too short a time period for the collapse to have been possible in air.

Considerable energy was used up in causing the observed massive high-speed sideways ejection of material (sometimes upwards) and much of the glass and concrete was pulverised and the ductile (not brittle) steelwork was shattered, twisted and mangled. The energy requirements to do anything even remotely like that rival the total amount of potential energy that the entire towers had to give when converted to kinetic energy, via gravity as the energy input. So while gravity is strong enough to cause reasonably dense objects to fall that far, through air, that fast, and while gravity is probably not strong enough to have so thoroughly disintegrated the towers under their own weight, gravity is certainly not strong enough to have done both simultaneously.

Why Did the WTC Towers fall, "fire and gravity" or something else?
In perfect conditions the maximum temperature that can be reached by hydrocarbons, like jet-fuel, burning in air is 825°C (1520°F) but these perfect conditions were not reached in the burning towers before collapse. There is absolutely no reason in the Bush-Cheney-PNAC-FEMA "truss theory" why there should have been any kind of fire in the basements at all to account for the molten steel found there. Thermal hotspots of around 1100°C (2000°F) were found in the basements on September 16th 2001. A thermite reaction (and explosives) generate extraordinarily high temperatures, greater than 2500°C (4550°F), and it provides a potentially credible explanation for the thermal hot spots and the molten steel around the basement level steel foundations. Construction steel has an extremely high melting point of about 1535°C (2800°F). Something other than gravity and fires melted the steel in the basements of the WTC complex.

The "Bush-Cheney razor blades and Saudi hijacker conspiracy theory" does not deal with the fact that we need to account for the molten steel in the basements through a hypothetical truss theory. A theory that implausibly speculates that fire high up in the building caused a "final straw" failure of a single truss support and gravity did the rest. Please remember that there is zero empirical evidence for this "truss theory" and it remains just a theoretical hypothesis.

Since buildings 1 and 2 survived the impact of the aircraft without collapsing (or signs of undue stress) and fire and gravity are claimed to have caused their collapse instead, then the aircraft are irrelevant as a mechanism for collapse except that they obviously caused some initial damage. In WTC7 aircraft are totally irrelevant to the mechanism of collapse since no aircraft ever hit the building. As the aircraft are irrelevant as the final mechanism of collapse, they are therefore simply a military deception "magician style visual pretext" for a collapse and not an ultimate cause of the collapse. Many eyewitnesses reported seeing and hearing explosions!

Turning to the video of where the collapse starts in all three buildings the timing sequence for the demolition appears to start around the area of the fires high up in buildings 1 and 2. However in the case of building 7, this building appears to have been demolished in a more conventional manner from the bottom, below the rather small fires that were in that building. Explosives used in the controlled demolition of buildings have to be detonated in precisely the correct order to achieve the desired collapse effect. When you carefully view the video of the collapse of buildings 1 and 2, (and 7) you will see "squibs" (or puffs of smoke shooting out sideways from the building). These squibs were several floors below the falling dust cloud and these slightly early detonations are an indication that explosives were used in the demolition of the buildings, not gravity alone.

The observed near free-fall times of the Twin Towers (and WTC7) were a dramatic signature of a controlled demolition. US (war criminal) regime measured times are around 10 to 12 seconds for WTC 1 & 2 and 6.6 seconds for the shorter WTC 7, which is close to calculated free-fall time in air, indicating the tower floors fell without much impediment. They essentially fell into air because the buildings had already lost all structural integrity. The collapse of WTC 7 in 6.6 seconds is just 0.6 of a second longer than it would take an object dropped from the roof to hit the ground so where is the delay that must be expected due to conservation of momentum, one of the foundational laws of physics? That is, as upper-falling floors strike lower floors and intact steel support columns the fall must be significantly impeded by the impacted mass. How do the upper floors fall so quickly and still conserve momentum in the collapsing buildings? The implausible theory put forth by "establishment" engineers is that while no steel members actually melted or failed in WTC 1 & 2, it was the "floor assemblies", bolted at their joists to the outer walls and inner core structures, that did fail. The floor joist attachment bolts were weakened by heat and gave way, twisting sideways and allowing the initial truss and then initial floor to "instantly unzip" itself all the way round the building and collapse onto the floor below. The remaining floors then "pancaked" all the way down at a speed of around 10 floors per second. Never mind that floor joist cross members, placed to resist twisting, and additional support structures were not included at all in the MIT/FEMA/NOVA/NIST calculations and presentations nor was a collapse mechanism for the very robust inner core of columns explained at all. Building WTC 7 has been totally ignored in the TV propaganda "expert documentary explanations" provided for the plebeian masses purporting to reassure us all that Saudis (mainly) and razorblades caused 9/11.

But consider the following; if the "pancaking" effect caused the total building failure, why is it that no video of either of the WTC 1 and 2 collapses shows any sign of stutter between floor collapses? Stutter should have been very apparent, especially in the first few floors of collapse when the speed of gravitational collapse had not accelerated for long. The first "unzipped" floor would only have fallen around 12 feet before hitting the next floor below. The exterior of the building should have been sliding down around the inner core, which should have remained largely sticking up in the air after the collapse. Consider also that apologists for the official Bush-Cheney conspiracy theory propose that 30% of the gravitational collapse energy was necessary to create the "pyroclastic" cloud of debris. That is, in the "official" analysis, this pulverising energy came out of the gravitational energy. This means that the time of fall would have been slowed further than what was observed. When a body of mass m falls from a height h, acted upon by gravitational acceleration g, it converts its potential energy PE = m x g x h into kinetic energy KE = (1/2) x m x (v exp2). Here h = (1/2) x g x (t exp2), t = time of fall, and v =g x t, where v = velocity. Removal of 30% of the PE to turn the concrete and asbestos into fine powder essentially reduces the amount of energy available from falling, effectively reducing the gravitational acceleration to something less than g. Substituting, in the above equations we have (1.0 - 0.3) x PE = 0.7 x PE = m x g' x h, where PE, m and h are as before and g' = the effective gravitational acceleration. Hence, comparing terms for PE, g' = 0.7 g. The time of collapse under g' will also increase. If we let the effective collapse time be t', then comparing terms for constant h, (1/2) x g x (t exp2) = (1/2) x g' x (t' exp2) = (1/2) x 0.7g x (t' exp2). Hence, (t exp2) = 0.7 x (t' exp2), or (t/t') = SQRT (0.7) = 0.837. Or, t' = 1.195 t. Now the observed time t = 10 seconds, a free fall time, the fastest possible time under g = 9.8m/sec/sec. For the dust cloud debris creation to absorb 30% of the gravitational energy, the observed time of fall would be 10s x 1.195, or almost 12 seconds, but on page 305 of the 9/11 Commission Report, we are told, in the government's "complete and final report" of 9/11 that the South Tower collapsed in 10 seconds. Here is the exact quote: "At 9:58:59, the South Tower collapsed in ten seconds". Clearly, there are serious flaws in the "official" explanation/conspiracy theory. The implication from the above is that there were major energy sources other than gravitational forces involved in the WTC tower collapses. In any event "common-sense" should tell us that gravity causing all the damage and providing the energy could not possibly propel steel beams out of the building sideways and even upwards towards space and away from the planet generating the gravity. In conclusion, the buildings could not possibly, following the laws of physics, have collapsed like that without explosives and/or the use of something like a thermite reaction. Nineteen disaffected Muslims (nine reportedly still strangely alive) armed with razorblades could not possibly have been involved in preparing WTC 1, 2 and 7 for demolition by those means and so perhaps we still need to catch and bring to justice the real terrorists of 9/11.

 

[bill smith]

Yea. Whom to believe. Whom to believe...

Who knows which way you will spring ? lol

 

[ozeco41]

...Imagine you have a 100 lb. metal weight being supported with 30 legs which together can support 300 lbs. This means 10 legs can just support the 100 lb. weight....

Please take care that this simplification does not mislead the non-engineers because it depends on which legs are removed. It is only true under some very specific situations.

Now remove 27 of the legs and what happens? The 100 lb. weight falls at 0.7g.

...so "ditto"

The 0.3g less than gravitational acceleration is not deceleration in the sense of effecting a transfer of momentum of the moving upper block to the lower structure. It is just minor resistance to the upper block's full acceleration due to gravity. To transfer momentum you need negative velocity change. With a 0.7g acceleration the velocity of the upper block continues to increase.

...the point we clarified yesterday.

Aside from the above, at a bare minimum a 3g deceleration of the upper block would be necessary to overload the core columns.

..if it was effectively loaded onto those columns which is highly unlikely. The probable result of the falling tilting block is an eccentric loading or glancing "miss" Even a total miss is possible but at that first fall most columns would still be joined - and bent either as part of the group that cascade failed to allow the initial collapse to start OR be the ones that were left with insufficient strength to hold the total and bent/buckled as a failure mode (plus the few already cut by aircraft). So the chance of columns carrying anything resembling original capacity is nearly non existent given that the start of the initial collapse would already have bent or buckled them. So lets not lose track of the sequence of events to postulate stages as if they were isolated from their context.

This deceleration or jolt just isn't there, and this proves something else was causing the lower structure columns to fail to support their load.

False dilemma - you are still missing the third option "OR the columns were not taking the load"

The upper block simply could not overload them without a negative velocity change due to a high deceleration of at least 3g.

...therefore this is a false assumption based on the false premise

...You couldn't be any more wrong about how you are stating this.

...well that is a "bit strong" why not say "wrong" or "in error" Surely there are many ways to be "more wrong"

 

[Tony Szamboti]

Yes, I saw it, but it's such an absurd fantasy that it's a little difficult to know how to respond to someone who could believe something so ridiculous. We have three legs each capable of supporting 10lbs and a weight of 100lb, so one or more of the legs will break. When they've broken, the weight will fall at 1g. That's assuming, of course, that the legs are made of some material with similar yield behaviour to steel. You seem to be suggesting that the remaining legs will continue to exert the same upward force after they've broken. I wonder what world you live in.


Exactly. If the resistance to the collapse gives less than 1g upward force, there will be no overall deceleration. If the upper block is falling at an angle, then the effective force from breaking individual structural elements will be averaged over a number of collisions, and will appear as a resistance to collapse, visible as a downward acceleration less than 1g. To see an absolute deceleration, you need a single impact across the entire block, which would only happen if all the columns collided simultaneously. Since we know the upper block fell at an angle, we know this didn't happen, so we don't expect a jolt. The resistance to collapse you claim not to see is just the difference between 1g and the actual downward acceleration. It's there, you just don't recognise it when you see it.

You've been told this a hundred times by many different people, all of whom understand exactly what's wrong with your paper. It's your failure to understand that's the problem.

Dave

Let's assume the columns were short. In that case they have to yield and fail by compressive rupture. The net effect is a downward acceleration of 0.7g.

The decleration which is needed to cause a transfer of momentum and amplified load of the statically insufficient load above the columns needs to come from a velocity change to the upper block velocity accumulated due to the 0.7g acceleration.

I am not misunderstanding anything. Now, in addition to your tortured "we don't expect a jolt" ramblings, you are just parsing words and throwing names around.

Dave, please tell us why Dr. Bazant thought it necessary for a jolt to have occurred to explain a natural mechanism for the collapses. Most shouldn't need it as it is painfully obvious, and you are now simply twisting words to eliminate that as a requirement for a natural collapse.

The game is over Dave. Those towers were taken down by controlled demolitions and the only reason we don't have a new investigation is political, not because there is no scientific proof of it.

 

[Dave Rogers]

I asked for mathematics, not a foaming-mouthed, disjointed rant. Maybe I wasn't clear. However, there were one or two numbers to be found.

Although the exact time of the collapse of WTC 1 and 2 cannot be determined with precision because of the growing dust cloud, each collapse took approximately 10-12 seconds.

So you're starting by stating that the collapses could have taken as long as 12 seconds. OK, although most informed observers would say more like 12-16; but let's take 12 seconds as your upper bound.

When a body of mass m falls from a height h, acted upon by gravitational acceleration g, it converts its potential energy PE = m x g x h into kinetic energy KE = (1/2) x m x (v exp2). Here h = (1/2) x g x (t exp2), t = time of fall, and v =g x t, where v = velocity. Removal of 30% of the PE to turn the concrete and asbestos into fine powder essentially reduces the amount of energy available from falling, effectively reducing the gravitational acceleration to something less than g. Substituting, in the above equations we have (1.0 - 0.3) x PE = 0.7 x PE = m x g' x h, where PE, m and h are as before and g' = the effective gravitational acceleration. Hence, comparing terms for PE, g' = 0.7 g. The time of collapse under g' will also increase. If we let the effective collapse time be t', then comparing terms for constant h, (1/2) x g x (t exp2) = (1/2) x g' x (t' exp2) = (1/2) x 0.7g x (t' exp2). Hence, (t exp2) = 0.7 x (t' exp2), or (t/t') = SQRT (0.7) = 0.837. Or, t' = 1.195 t. Now the observed time t = 10 seconds, a free fall time, the fastest possible time under g = 9.8m/sec/sec. For the dust cloud debris creation to absorb 30% of the gravitational energy, the observed time of fall would be 10s x 1.195, or almost 12 seconds,

So now you're saying that the collapse times would be expected to be almost 12 seconds.

Let's get this straight. The collapses should have taken just under 12 seconds, whereas they actually took between 10 and 12 seconds.

Gosh, now I'm suspicious.

Dave

 

[Shrinker]

Additionally it is clear from video of the WTC2 event that the top load tipped over to the East, so did not apply a symmetrical weight load to the tower below yet within about 2 seconds of the explosive collapse initiation, the top load was explosively disassembled in mid-air upwards. Moreover for the initial symmetrical explosive collapse process below the tipped over top, during the first few seconds the ripple down, explosive blow outs shot down the tower faster than the explosively ejected building material from the top could keep up. This means that in the initial stage of the "WTC2 collapse process" the symmetrical-ripple-down-explosiveness, purportedly from a top load exerting an asymmetrical weight load, since it had tipped over before it was explosively disassembled upwards, was faster than the time for a reasonably dense object to fall through air.

I feel explosively strange after explosively reading this explosive paragraph. Like some explosively subliminal process has explosively affected me. Do I seem explosively okay?

 

[Disbelief]

It was accepted? Well great. I noticed the thread was closed because Parky showed up and began the derailment as is standard fare for him/her.

1. So someone here decided to take on the challenged then backed out because Heiwa didn't answer some questions?
If I recall, they demanded part of the money be put into escrow, correct? But that wasn't part of Hewais challenge, correct? Model it and he will pay. Quite simple really. By changing the challenge that is simply a passive-aggressive way of avoiding the challenge all together. Which means the challenge still stands and is still completely avoided by engineers, scientists, etc.

Would you pay a substantial amount of your own money with no proof that the challenger actually has the money? This is a smart thing to do, since Heiwa really hasn't proven he has any substantial portion of the million he claims.

2. Strange to avoid science when it is so easy to do, eh? Why do people at JREF fear science, Disbelief?

Science is all over this forum, with only the TM that fails to read. How many calculations has the TM provided to real peer reviewed journals for publishing? Why does the TM get ripped apart by the posters here whenever they do post their calculations?

3. So let me get this straight, someone will do it for money, but not do it to support the WTC 1 official collapse scenario?

Are you spending your own money to try and support your silly ideas? Why should someone else do so, when the math proves the widely accepted belief in how the towers collapsed from fire and structural damage?

4. Don't you think, Disbelief, NIST would have modeled it if an anonymous poster on this site could easily model the collapse to prove Hewia wrong?

Maybe, as pointed out in the challenge thread, Heiwa's challenge is not really truly representative of what happened. Therefore, the person accepting the challenge is doing so, just to prove Heiwa is wrong on what he is stating.

5.If so, doesn't this make NIST look just a tad bit incompetent?

Once again, since Heiwa's challenge does not really represent the collapse of the towers, NIST is in no way shown incompetent. The only incompetence displayed is the TM who is thinking this challenge really represents reality.

 

[twinstead]

Please don't tell me anybody thinks Heiwa's "Challenge" has anything to do with what actually happened at the WTC on 9/11. To me it's just an abstract exorcise, something engineers would do for fun at parties or something.

 

[Dave Rogers]

Let's assume the columns were short. In that case they have to yield and fail by compressive rupture. The net effect is a downward acceleration of 0.7g.

It's like trying to argue with someone who truly believes the sky is yellow - there's simply no point of contact between you and reality. At some point the columns break, and if they're made of steel that fracture occurs at a shortening that's at most less than 1% of their original length. After they break, they're not as strong as they were before they broke. I can't believe I'm trying to explain this.

Dave, please tell us why Dr. Bazant thought it necessary for a jolt to have occurred to explain a natural mechanism for the collapses.

He didn't. The jolt is your fantasy. Bazant calculated a limiting case, which was not intended to describe the actual details of the collapse.

The game is over Dave. Those towers were taken down by controlled demolitions and the only reason we don't have a new investigation is political, not because there is no scientific proof of it.

A convenient excuse for why your ramblings will never be taken seriously, to be sure. So is the Obama administration part of the conspiracy too now?

Your supposed scientific proof is laughable. No informed and unbiased observer takes any of it seriously for a moment. Whatever the political situation, that's why you don't have your new investigation.

Dave

 

[ozeco41]

I asked for mathematics, not a foaming-mouthed, disjointed rant. Maybe I wasn't clear. However, there were one or two numbers to be found......

Dave be assured that your descriptions are good enough - certainly "headed in the right direction" and Tony is using debating tricks in his attempt to throw you.

His model is flawed - it has a similar flaw to Greenings work and I suspect Bazants work exccept that Bazant is a past master of writing "Academic Speak Gobledegook" to look impressive whilst obscuring what he is really saying. Greening at least makes his wrong assumption explicit and open.

The difference for Greening, Bazant and probably others is that there was so much energy available that they still proved "collapse" even though the method was wrong.

Tony is still playing word games with "Jolt" when he means a big Jolt to support his explanation. Of course there were jolts. But not the big ones his expalanation needs. He would be better of correcting his modeling but with his current political alliance that path is probably not viable for him.

The old saying "choose your friends wisely"

His legs model plays deliberately or accidentally on the lay persons expectation that removing one quarter of legs would add an additional one third load to the other remaining legs. Not necessarily so. I can draw a simple arrangement where removing 1/4 of the legs doubles the load on some of the remaining legs. And that by the way is a key factor often misunderstood in the initial collapse cascade.

Remember also that legal practitioners maxim "When you have no case attack the witnesses" AND the corollary "When they attack the witnesses they probably have no case."

Cheers.

Eric C

 

[ozeco41]

Please don't tell me anybody thinks Heiwa's "Challenge" has anything to do with what actually happened at the WTC on 9/11. To me it's just an abstract exorcise, something engineers would do for fun at parties or something.

OK I won't tell you that.

It has no resemblance to what happened at WTC on 9/11.

It has a superficial appearance of being true but even that has flaws.

He defines it with ambiguity to allow "escape holes".

I have challenged him several times BUT refused to take on the technical side of the challenge because of the ambiguity of definitions (plus it is a waste of time)

 

[Tony Szamboti]

It's like trying to argue with someone who truly believes the sky is yellow - there's simply no point of contact between you and reality. At some point the columns break, and if they're made of steel that fracture occurs at a shortening that's at most less than 1% of their original length. After they break, they're not as strong as they were before they broke. I can't believe I'm trying to explain this.



He didn't. The jolt is your fantasy. Bazant calculated a limiting case, which was not intended to describe the actual details of the collapse.



A convenient excuse for why your ramblings will never be taken seriously, to be sure. So is the Obama administration part of the conspiracy too now?

Your supposed scientific proof is laughable. No informed and unbiased observer takes any of it seriously for a moment. Whatever the political situation, that's why you don't have your new investigation.

Dave

Dave, you couldn't get a model to do what you propose in a million years and you are just playing games.

What I am saying could be replicated everytime, and anyone here who has a high speed camera could build a two story model with a weight at the top and remove the columns from the second story and prove the weight will decelerate when it impacts the first story columns. However, if the first story columns are removed also, the weight will not decelerate. This is what really happened in those towers and you can try and trick all the people you want, but anyone with a scientific background will see through your false argument.

Bazant said there needed to be a jolt because that is the only way a statically insufficient load above can overcome a structure below, which is designed to support several times that load.

 

[Dave Rogers]

Dave be assured that your descriptions are good enough - certainly "headed in the right direction" and Tony is using debating tricks in his attempt to throw you.

Oh, don't worry, I've argued with Tony before, and I'm fairly resigned to the fact that I'll never be on his Christmas card list. I just find it incredible that anyone can believe the things he claims to believe and still be able to count to five.

Dave

 

[Grizzly Bear]

THe obsession with a visible jolt is as bizarre as Psybillyhackrs' (can't get the spelling of his name right if my life depended on it) obsession with the mass of concrete and steel inside the building's...

 

[AndrewIlluminatus]

So now you're saying that the collapse times would be expected to be almost 12 seconds.

Let's get this straight. The collapses should have taken just under 12 seconds, whereas they actually took between 10 and 12 seconds.

Gosh, now I'm suspicious.

Dave

Why did you dishonestly stop and clip half way through the sentence?

"For the dust cloud debris creation to absorb 30% of the gravitational energy, the observed time of fall would be 10s x 1.195, or almost 12 seconds, but on page 305 of the 9/11 Commission Report, we are told, in the government's "complete and final report" of 9/11 that the South Tower collapsed in 10 seconds. Here is the exact quote: "At 9:58:59, the South Tower collapsed in ten seconds". Clearly, there are serious flaws in the "official" explanation/conspiracy theory."


So let's just say, for the sake of simplicity, that our falling object has a mass of 1. (The object's mass will affect its energy, and its momentum, but not its rate of free-fall.)

The potential energy given up by falling 3 seconds (144 ft) is 1 x 32 x 144 = 4608

The kinetic energy gained after falling 3 secs is 1/2 x 1 x 96(squared) = 1/2 x 9216 = 4608

So, all of the available potential energy was converted to kinetic energy. Seeing that energy was, in fact, conserved is how we know that the answer in The Simplest Case, above, was correct. We've checked our work, using an independent analysis, based upon the sound principle of conservation of energy. Now, and only now, we can be certain that our answer was correct.


One Little Complication

Air resistance.

The free-fall equations reflect a perfect, frictionless world. They perfectly predict the behaviour of falling bodies in a vacuum. In fact, some of you may have seen a science class demonstration in which the air is pumped out of a tube and then a feather will fall, in that vacuum, as fast as will a solid metal ball.

That's how parachutes work: much of the falling object's potential energy gets expended doing the work of pushing a lot of air out of the way in order for the object to fall. As a result, not all of the potential gravitational energy can go towards accelerating the object downward at gravity's maximal rate of 32 ft/sec/sec.

In other words, only when there is zero resistance can any falling object's potential energy be completely converted into kinetic energy. Anything which interferes with any falling object's downward acceleration will cause its acceleration to be reduced from the maximum gravitational acceleration of 32 feet per second per second, as some of gravity's potential energy is consumed doing work overcoming resistance.

That's why you may have heard the term "terminal velocity". The free-fall equations predict that a falling object's velocity will continue to increase, without limit. But in air, once a falling object reaches a certain speed, it's propensity to fall will be matched by air's resistance to the fall. At that point the object will continue to fall, but its speed will no longer increase over time.

A Quick Recap

Earth's gravity causes objects to fall. They fall according to precise, well-known equations. The equations assume no (air) resistance. Any resistance at all will cause the object to fall less rapidly than it would have without that resistance.

It is that last sentence which bears repeating.

There is a maximum possible rate at which objects fall, and if any of gravity's potential energy is consumed doing anything other than accelerate the object downward -- even just having to push air out of the way -- there will be less energy available to accelerate the object downward, and so that object's downward acceleration will be diminished.

And if an object's downward acceleration is diminished, it will be going slower along the way, and thus it will take longer to fall a given distance.

Free-falling from WTC heights

The towers were 1350 and 1360 feet tall. So let's start by using our trusty free-fall equation to see how long it should take an object to free-fall from the towers' former height.

Distance = 1/2 x Gravity x Time(squared)

or

Time(squared) = (2 x Distance) / Gravity

Time(squared) = 2710 / 32 = 84.7

Time = 9.2

So our equation tells us that it will take 9.2 seconds to free-fall to the ground from the towers' former height.

Using our simpler equation, V = GT, we can see that at 9.2 seconds, in order to reach the ground in 9.2 seconds, the free-falling object's velocity must be about 295 ft/sec, which is just over 200 mph.

But that can only occur in a vacuum. Not in air at about 1.2Kg per cubic metre density.

Since the WTC was at sea level, in Earth's atmosphere, you might be able to imagine how much air resistance that represents. (Think about putting your arm out the window of a car moving half that fast!) Most free-falling objects would reach their terminal velocity long before they reached 200 mph. For example, the commonly-accepted terminal velocity of a free-falling human is around 120 mph. The terminal velocity of a free-falling cat is around 60 mph.

Therefore, air resistance alone will make it take longer than 10 seconds for gravity to pull an object to the ground from the former height of WTC2.

There is essentially no resistance from the intact structure shown and so no sequential kinetic energy collisions could have taken place in the official number of 10 seconds for WTC2 (12 seconds for WTC1). What is the sound of one hand clapping? No sequential and mutually annihilating explosive impacts took place in towers offering essentially no resistance to the collapse process, so the towers evidently exploded by some other method than gravity supplying any energy. The steel frame towers below (the already explosively disassembled tops) offered less resistance to the "collapse process" than if they had been made out of wood and chewing gum. They offered no more resistance than air and less resistance than if the already explosively disassembled tops had been falling through water instead of through a highly robust steel frame structure.

 

[Dave Rogers]

Bazant said there needed to be a jolt because that is the only way a statically insufficient load above can overcome a structure below, which is designed to support several times that load.

No, he didn't. There only has to be a measurable jolt if the entire structure is overwhelmed at the same time. If individual structural elements are fractured separately at different times, then the series of very small jolts will be seen as an overall reduction in the downward acceleration, as everyone keeps trying to tell you.

As for your bizarre claim about the 0.7g acceleration of the weight with only three legs, it contradicts Hooke's law for a start, and everything that's ever been known about plastic deformation to continue. In fact, it's absurd enough for an award.

Dave

 

[dtugg]

Why did you dishonestly stop and clip half way through the sentence?

"For the dust cloud debris creation to absorb 30% of the gravitational energy, the observed time of fall would be 10s x 1.195, or almost 12 seconds, but on page 305 of the 9/11 Commission Report, we are told, in the government's "complete and final report" of 9/11 that the South Tower collapsed in 10 seconds. Here is the exact quote: "At 9:58:59, the South Tower collapsed in ten seconds". Clearly, there are serious flaws in the "official" explanation/conspiracy theory."

The collapse clearly took longer than 10 seconds. I couldn't care less about a minor mistake in a report that had nothing to do with explaining the collapses.

 

[Dave Rogers]

Why did you dishonestly stop and clip half way through the sentence?

"For the dust cloud debris creation to absorb 30% of the gravitational energy, the observed time of fall would be 10s x 1.195, or almost 12 seconds, but on page 305 of the 9/11 Commission Report, we are told, in the government's "complete and final report" of 9/11 that the South Tower collapsed in 10 seconds. Here is the exact quote: "At 9:58:59, the South Tower collapsed in ten seconds". Clearly, there are serious flaws in the "official" explanation/conspiracy theory."

Because it's idiotic. You're trying to claim that the collapse time was something other than what it should have been, yet you end up proving that it's exactly what it should have been. The fact that the 9/11 Commission Report approximates the collapse time is irrelevant. If the towers fell in 12 seconds, they fell in 12 seconds.

Still, enjoy your ranting. Someone should.

Dave

 

[ozeco41]

And the NIST Brief stopped at the point where "global collapse was inevitable" - which every competent engineer who is aware of how it collapsed would agree.

So it really is a not so clever trick to pretend otherwise.

My focus (one of them) for 18 months has been on explaining how the global collapse occurred for genuinely interested lay persons. Not trying to convert the believers - most are beyond recovery with some mix of limited understanding/intellect OR political alliance ties and loyalties to "honour" if that is correct word for untruthfulness.

 

[tsig]

Although the exact time of the collapse of WTC 1 and 2 cannot be determined with precision because of the growing dust cloud, each collapse took approximately 10-12 seconds. NIST NCSTAR "Within 12s, the collapse of WTC1 had left nothing but rubble." Only 2 seconds slower than the time for a reasonably dense object that was not overly influenced by air buoyancy at 1.2kg/cubic metre (and air drag), to fall from the WTC roof to the plaza. Therefore, air resistance alone will make it take longer than 10 seconds for gravity to pull an object to the ground from the former height of WTC1 or 2 (time would be about 9.2 seconds in a vacuum). That 12s represents extraordinarily insufficient resistance within the intact tower structure to have permitted the kind of impacts imagined to produce sequential kinetic energy impacts and kinetic energy explosions in a ripple down manner. The energy from gravity has to be used up and it cannot be expected to do two jobs at once. Either all the energy from gravity is used up to create imagined tonnes of TNT kinetic energy explosiveness in sequential one-off explosive ripple-down events or it is used up to get an already explosively disassembled (by other means) building to the ground in that sort of time frame.

Additionally it is clear from video of the WTC2 event that the top load tipped over to the East, so did not apply a symmetrical weight load to the tower below yet within about 2 seconds of the explosive collapse initiation, the top load was explosively disassembled in mid-air upwards. Moreover for the initial symmetrical explosive collapse process below the tipped over top, during the first few seconds the ripple down, explosive blow outs shot down the tower faster than the explosively ejected building material from the top could keep up. This means that in the initial stage of the "WTC2 collapse process" the symmetrical-ripple-down-explosiveness, purportedly from a top load exerting an asymmetrical weight load, since it had tipped over before it was explosively disassembled upwards, was faster than the time for a reasonably dense object to fall through air.

On page 305 of the 9/11 Commission Report, we are told, in the government's "complete and final report" of 9/11 that the South Tower collapsed in 10 seconds. Here is the exact quote: "At 9:58:59, the South Tower collapsed in ten seconds". Actually that is probably slightly too short a time period for the collapse to have been possible in air.

Considerable energy was used up in causing the observed massive high-speed sideways ejection of material (sometimes upwards) and much of the glass and concrete was pulverised and the ductile (not brittle) steelwork was shattered, twisted and mangled. The energy requirements to do anything even remotely like that rival the total amount of potential energy that the entire towers had to give when converted to kinetic energy, via gravity as the energy input. So while gravity is strong enough to cause reasonably dense objects to fall that far, through air, that fast, and while gravity is probably not strong enough to have so thoroughly disintegrated the towers under their own weight, gravity is certainly not strong enough to have done both simultaneously.

Why Did the WTC Towers fall, "fire and gravity" or something else?
In perfect conditions the maximum temperature that can be reached by hydrocarbons, like jet-fuel, burning in air is 825°C (1520°F) but these perfect conditions were not reached in the burning towers before collapse. There is absolutely no reason in the Bush-Cheney-PNAC-FEMA "truss theory" why there should have been any kind of fire in the basements at all to account for the molten steel found there. Thermal hotspots of around 1100°C (2000°F) were found in the basements on September 16th 2001. A thermite reaction (and explosives) generate extraordinarily high temperatures, greater than 2500°C (4550°F), and it provides a potentially credible explanation for the thermal hot spots and the molten steel around the basement level steel foundations. Construction steel has an extremely high melting point of about 1535°C (2800°F). Something other than gravity and fires melted the steel in the basements of the WTC complex.

The "Bush-Cheney razor blades and Saudi hijacker conspiracy theory" does not deal with the fact that we need to account for the molten steel in the basements through a hypothetical truss theory. A theory that implausibly speculates that fire high up in the building caused a "final straw" failure of a single truss support and gravity did the rest. Please remember that there is zero empirical evidence for this "truss theory" and it remains just a theoretical hypothesis.

Since buildings 1 and 2 survived the impact of the aircraft without collapsing (or signs of undue stress) and fire and gravity are claimed to have caused their collapse instead, then the aircraft are irrelevant as a mechanism for collapse except that they obviously caused some initial damage. In WTC7 aircraft are totally irrelevant to the mechanism of collapse since no aircraft ever hit the building. As the aircraft are irrelevant as the final mechanism of collapse, they are therefore simply a military deception "magician style visual pretext" for a collapse and not an ultimate cause of the collapse. Many eyewitnesses reported seeing and hearing explosions!

Turning to the video of where the collapse starts in all three buildings the timing sequence for the demolition appears to start around the area of the fires high up in buildings 1 and 2. However in the case of building 7, this building appears to have been demolished in a more conventional manner from the bottom, below the rather small fires that were in that building. Explosives used in the controlled demolition of buildings have to be detonated in precisely the correct order to achieve the desired collapse effect. When you carefully view the video of the collapse of buildings 1 and 2, (and 7) you will see "squibs" (or puffs of smoke shooting out sideways from the building). These squibs were several floors below the falling dust cloud and these slightly early detonations are an indication that explosives were used in the demolition of the buildings, not gravity alone.

The observed near free-fall times of the Twin Towers (and WTC7) were a dramatic signature of a controlled demolition. US (war criminal) regime measured times are around 10 to 12 seconds for WTC 1 & 2 and 6.6 seconds for the shorter WTC 7, which is close to calculated free-fall time in air, indicating the tower floors fell without much impediment. They essentially fell into air because the buildings had already lost all structural integrity. The collapse of WTC 7 in 6.6 seconds is just 0.6 of a second longer than it would take an object dropped from the roof to hit the ground so where is the delay that must be expected due to conservation of momentum, one of the foundational laws of physics? That is, as upper-falling floors strike lower floors and intact steel support columns the fall must be significantly impeded by the impacted mass. How do the upper floors fall so quickly and still conserve momentum in the collapsing buildings? The implausible theory put forth by "establishment" engineers is that while no steel members actually melted or failed in WTC 1 & 2, it was the "floor assemblies", bolted at their joists to the outer walls and inner core structures, that did fail. The floor joist attachment bolts were weakened by heat and gave way, twisting sideways and allowing the initial truss and then initial floor to "instantly unzip" itself all the way round the building and collapse onto the floor below. The remaining floors then "pancaked" all the way down at a speed of around 10 floors per second. Never mind that floor joist cross members, placed to resist twisting, and additional support structures were not included at all in the MIT/FEMA/NOVA/NIST calculations and presentations nor was a collapse mechanism for the very robust inner core of columns explained at all. Building WTC 7 has been totally ignored in the TV propaganda "expert documentary explanations" provided for the plebeian masses purporting to reassure us all that Saudis (mainly) and razorblades caused 9/11.

But consider the following; if the "pancaking" effect caused the total building failure, why is it that no video of either of the WTC 1 and 2 collapses shows any sign of stutter between floor collapses? Stutter should have been very apparent, especially in the first few floors of collapse when the speed of gravitational collapse had not accelerated for long. The first "unzipped" floor would only have fallen around 12 feet before hitting the next floor below. The exterior of the building should have been sliding down around the inner core, which should have remained largely sticking up in the air after the collapse. Consider also that apologists for the official Bush-Cheney conspiracy theory propose that 30% of the gravitational collapse energy was necessary to create the "pyroclastic" cloud of debris. That is, in the "official" analysis, this pulverising energy came out of the gravitational energy. This means that the time of fall would have been slowed further than what was observed. When a body of mass m falls from a height h, acted upon by gravitational acceleration g, it converts its potential energy PE = m x g x h into kinetic energy KE = (1/2) x m x (v exp2). Here h = (1/2) x g x (t exp2), t = time of fall, and v =g x t, where v = velocity. Removal of 30% of the PE to turn the concrete and asbestos into fine powder essentially reduces the amount of energy available from falling, effectively reducing the gravitational acceleration to something less than g. Substituting, in the above equations we have (1.0 - 0.3) x PE = 0.7 x PE = m x g' x h, where PE, m and h are as before and g' = the effective gravitational acceleration. Hence, comparing terms for PE, g' = 0.7 g. The time of collapse under g' will also increase. If we let the effective collapse time be t', then comparing terms for constant h, (1/2) x g x (t exp2) = (1/2) x g' x (t' exp2) = (1/2) x 0.7g x (t' exp2). Hence, (t exp2) = 0.7 x (t' exp2), or (t/t') = SQRT (0.7) = 0.837. Or, t' = 1.195 t. Now the observed time t = 10 seconds, a free fall time, the fastest possible time under g = 9.8m/sec/sec. For the dust cloud debris creation to absorb 30% of the gravitational energy, the observed time of fall would be 10s x 1.195, or almost 12 seconds, but on page 305 of the 9/11 Commission Report, we are told, in the government's "complete and final report" of 9/11 that the South Tower collapsed in 10 seconds. Here is the exact quote: "At 9:58:59, the South Tower collapsed in ten seconds". Clearly, there are serious flaws in the "official" explanation/conspiracy theory. The implication from the above is that there were major energy sources other than gravitational forces involved in the WTC tower collapses. In any event "common-sense" should tell us that gravity causing all the damage and providing the energy could not possibly propel steel beams out of the building sideways and even upwards towards space and away from the planet generating the gravity. In conclusion, the buildings could not possibly, following the laws of physics, have collapsed like that without explosives and/or the use of something like a thermite reaction. Nineteen disaffected Muslims (nine reportedly still strangely alive) armed with razorblades could not possibly have been involved in preparing WTC 1, 2 and 7 for demolition by those means and so perhaps we still need to catch and bring to justice the real terrorists of 9/11.

Are you being paid by the word?