Physics of 9/11...

Originally posted by Joey Canoli

Originally posted by Azp420

But we did not see columns sticking up in the air above the wave of destruction.

This proves your ignorance.

Google WTC spire and let me know if you changed your mind.

If you cannot, then you are insane.

I googled it quickly and I could not find anything that contradicts the exact wording of my statement.

I think there's a consensus, even fromtruthers, that it was at about 70% of FFA.

If you think this is still too fast, present your evidence, not your incredulity.

70% free fall is what I would define as "anything close to" free fall acceleration. It is impossible to get 100% outside of a vacuum but the structure is supposed to provide massive resistance.

I will elaborate on why this is too "fast" if Bazant's model is to be taken as accurate. Bazant estimates that 70% of the kinetic energy is dissipated each time a floor impacts. The main problem is what I pointed out in my last post:

Originally posted by Azp420
Anyone with a basic understanding of physics (specifically conservation of energy principles) can see that if 70% of the kinetic energy is dissipated each time a floor impacts, there is no way near enough energy to maintain a free-fall (or anything close to) acceleration. To achieve a free-fall (or anything close to) acceleration, all the gravitational potential energy must be converted to kinetic energy and remain as kinetic energy. As soon as large amounts of kinetic energy are lost, the mass should decelerate (again, like in the OP video, this is where we should see jolts). This is a very basic concept and shouldn't need a link to a scientific paper full of calculations to prove it. Do you disagree with this concept?

Maybe you do not appreciate the significance of losing 70% of its kinetic energy each time a floor impacts. This means each time the falling mass impacts the next floor below, it retains only 30% of its kinetic energy (but it somehow still manages 70% free fall).

The formula for kinetic energy, E = 0.5*m*v^2

m=mass
v=velocity

Let the kinetic energy during an arbitrary point in the collapse be E1.

Let the kinetic energy during the point in collapse exactly one floor below the point in E1 be E2 (and the same for m & v).

E1 = 0.5*m1*v1^2
E2 =0.5*m2*v2^2

E2 = 0.3*E1

E2 = 0.3*(0.5*m1*v1^2)

This means one of the variables (or a proportional combination of both) is only 30% of what it was the floor above.

Lets take an ultra conservative assumption that the mass remains about the same, ie floors are being pulverized into dust at the same rate as they are collected. In reality, the falling mass would be increasing but that only helps my argument.

Say m1 = m2

therefore

v2^2 = 0.3*(v1^2)

v2 = 0.55*v1

Under even the most conservative assumption, with each floor impact the velocity of the downward falling mass should only be about half of what it was one floor higher. This is obviously not the case, therefore 70% free fall acceleration is far too high, and Bazant's model of the collapse is highly inaccurate, and that is the best the official story can link to.

And again, it was about 70% FFA.

Support your opinion with facts.

Done. Sorry, i thought I was pointing out the obvious to someone who claims to have a good understanding of physics.

An objection of 250C creep to failure in 1 hour should be accompanied by engineering support, not incredulity.

I was referring to the two hour fire proofing that existed in WTC7. I don't need a technical report to show how a two hour fire rating ensures a structures stability and integrity for two hours.









[edit on 26-7-2010 by Azp420]

Originally posted by Joey Canoli

The proof that this is exactly what happens in the real world, and your misapplication of physics is proven in verinage. The top part crushes down the bottom part, with virtually zero crush up until the top reaches the ground.

You cannot dispute this fact with anything but incredulity, for you have zero facts to support it.

What? Huge crush up occurs in almost all the examples. Certain structural members are also severed beforehand to ensure the desired mode of collapse is achieved.

Originally posted by weedwhacker

Gravity. Force. Mass. Acceleration. F = MA

The physics are undeniable.

You can't just yell out some physics words and an equation then claim the physics are undeniable.

Originally posted by Azp420

I googled it quickly and I could not find anything that contradicts the exact wording of my statement.

Then something is wrong with you.

There are core columns sticking up after the collapse wave passes for about 20-30 seconds.

It is impossible to get 100% outside of a vacuum but the structure is supposed to provide massive resistance.

Incredulity noted.

Zero support noted.

Lets take an ultra conservative assumption that the mass remains about the same, ie floors are being pulverized into dust at the same rate as they are collected.

Conservative how?

It only helps your arguement to make that unrealistic assumption.

In reality, the falling mass would be increasing but that only helps my argument.

Liar, it hurts your arguement.

This is obviously not the case, therefore 70% free fall acceleration is far too high, and Bazant's model of the collapse is highly inaccurate, and that is the best the official story can link to.

Nope. It shows that similar to the spire issue, you are ignorant of what Bazant says:

www.civil.northwestern.edu...&%20Did%20Not%20Cause%20It.pdf

" Eq. (21) indicates the dissipation of about 865 J per kg of pulverized concrete, which is a
realistic value.
The total gravitational potential energy g released by one tower is calculated as the tower
weight multiplied by the distance between the mass centroid of the tower and the mass centroid
of the rubble heap on the ground, and is approximately g = 8.25×1011 J. Eq. (21) represents
only about 7.65 % of 2g (both towers). So there is far more impact energy than necessary."

You've misread the ".7 gamma" quote you gave and what it represents. That is the factor for concrete breakage *only*, which as he explained above, takes 7.65% of the PE.

Sorry, i thought I was pointing out the obvious to someone who claims to have a good understanding of physics.

I do.

Which is how I caught your error.

I was referring to the two hour fire proofing that existed in WTC7. I don't need a technical report to show how a two hour fire rating ensures a structures stability and integrity for two hours.

Why are you now dodging?

You stated that steel can't fail at 250C. The point was being made about the towers, not 7. That clearly refers to the temp of the steel, not the air temp, nor whether or not insulation is present.

Now you're saying that steel can't fail cuz of the insulation in 7.

This is the third instance of proof of the lack of attention to detail from you: spires, .7 gamma, 250C.

I suggest you read carefully from now on.

Originally posted by Azp420

What? Huge crush up occurs in almost all the examples.

Nope.

Certain structural members are also severed beforehand to ensure the desired mode of collapse is achieved.

Nope.

There is typically zero prep work done below the initiation zone.

reply to post by Joey Canoli

Then something is wrong with you.

Ouch. Why can't you have a professional discussion with anyone who has an opposing viewpoint?

There are core columns sticking up after the collapse wave passes for about 20-30 seconds.

We do not see anything sticking up above the wave of destruction. It is only after the wave of destruction dissipates and the dust settles that we see the remaining columns sticking up. The video you posted doesn't even contain the wave of destruction. The point I was making was why don't we see columns sticking up near where the plane impacted after the floors have pancaked down (while the unbraced length of the columns are still not too high)?

Conservative how?

It only helps your arguement to make that unrealistic assumption.

Liar, it hurts your arguement.

Now you call me a liar? Either you are getting desperate and lying yourself, or you really are ignorant about the kinetic energy equation. I will explain why my assumption was conservative.

E = 0.5*m*v^2

We are decreasing E by a fixed amount. For the equation to remain true, m or v or both must decrease. For simplicity's sake I kept m constant (we both agree it would actually increase). If we increase m, for the equation to still equal a lower E, v must decrease by even more than it would have had m remained constant. In other words, if m increases, to keep the equation balanced v must decrease. Like I said, I made an ultra conservative assumption.

" Eq. (21) indicates the dissipation of about 865 J per kg of pulverized concrete, which is a
realistic value.
The total gravitational potential energy g released by one tower is calculated as the tower
weight multiplied by the distance between the mass centroid of the tower and the mass centroid
of the rubble heap on the ground, and is approximately g = 8.25×1011 J. Eq. (21) represents
only about 7.65 % of 2g (both towers). So there is far more impact energy than necessary."

You've misread the ".7 gamma" quote you gave and what it represents. That is the factor for concrete breakage *only*, which as he explained above, takes 7.65% of the PE.

I was not referring to equation 21, I was referring to equation 11. I am not arguing about whether enough potential energy existed to pulverize all the concrete into dust. I am arguing about the rate of acceleration of the falling mass when taking into account what Bazant claims is the amount of kinetic energy dissipation per unit height. This is a huge flaw in the model so stop directing attention away from it. I disagree that I have misread or misrepresented anything. I will quote to what I was referring straight from Bazant's paper.

The energy per unit height, Fs, that is dissipated by comminution of concrete floor slabs, can be calculated from the comminution theory.

He then gives the equation for Fs as

Fs = (gamma)*(Kc/h)

where (Kc/h) is the kinetic energy of a single story divided by the inter-story height of that story.

Coefficient (gamma) has been inserted in Eq. (11) as an empirical coefficient of comminution effectiveness, specifying the fraction of Kc that is dissipated by the work of comminution.

gamma is estimated to be 0.7.

In Bazant's own words, he states the fraction of kinetic energy that is dissipated in each floor due to the work done by comminution is 0.7, or 70%.

A major concern is the amount of estimations and assumptions throughout the entire model. Each time an estimation or assumption is made the accuracy of the model decreases. Bazant has come up with a very nice approximate model but it is limited to just that. It does not prove the OS. The OS has not been able to be replicated with experimentation. We want to know precisely what happened.

reply to post by Joey Canoli

Sorry, i thought I was pointing out the obvious to someone who claims to have a good understanding of physics.

I do.

Which is how I caught your error.

We are yet to see your understanding of physics displayed. So far all you have done is direct people to Bazant's work. You made an error in catching my "error" (which as I've pointed out was not an error) and copy-pasted an irrelevant section of Bazant's paper.

Why are you now dodging?

You stated that steel can't fail at 250C. The point was being made about the towers, not 7. That clearly refers to the temp of the steel, not the air temp, nor whether or not insulation is present.

Actually, I stated on multiple occasions in this thread that steel can fail at any temperature. I never made the statement you are alleging (of-course unless you quote me out of context again). I am also not dodging anything, I was never in a discussion with you about temperature creep in the towers.

I suggest you read carefully from now on.

Is this another tactic because you are unable to debate me on the physics? I would take a look at yourself. Throughout this discussion you have been either intentionally or unintentionally misrepresenting what I have said, I'm not sure which is worse.

Nope.

Yes. If you look carefully you can see crush up. If you look carefully you will also see something else in each of the structures. After initiation the structure greatly accelerates through the weakened initiation zone (clearly visible in most cases, ~2 - 5 stories). Once the falling top mass encounters the stronger structure below the initiation zone it does not continue to accelerate (especially not at 70% free fall). It decelerates after the initial burst of near free fall acceleration. This deceleration is a lot more vivid in some of the examples than others. Keep your eye on the roof line. It will be at maximum velocity right before the top half impacts the structure below the initiation zone. In none of the structures is a higher velocity than this achieved (no downwards acceleration). In most of the structures you can see significantly lower velocities after impact (downwards deceleration).

The point I am making is that it is almost impossible for a portion of a properly designed and undamaged structure to accelerate through the rest of the structure (it would have to be a very unusual structure to do so), yet they want us to buy that that happened on 9/11 (and at 70% free fall!).

Nope.

There is typically zero prep work done below the initiation zone.

Yes. There is prep work done below the initiation zone. I'm not too concerned though, as the video you have provided does an excellent job at proving one of my points.



[edit on 28-7-2010 by Azp420]

Originally posted by ANOK
reply to post by weedwhacker

 

Again the evidence you all keep ignoring...

The tops did not do what the top did in that verinage demolition.

Yeap, this is damning evidence which they are ignoring.

This 15 story mass (which is supposed to crush down on the rest of the tower then crush up on itself once it has finished doing that) disintegrates itself on many floors at once, BEFORE the wave of destruction begins to destroy the intact structure below the aircraft impact zone. Bazant's model is extremely inaccurate because it does not describe this happening or how this happens.

reply to post by Azp420


He also ignores and fails to explain the top of WTC 2...



Even more damning than WTC 1.

Anyone who has had anything to do with engineering should know that to have something act as a piston, and crush something straight down symmetrically, it has to be sitting square (true) not at an angle.

Simple, no need to even go into 'angular moment' and the hows and whys. Common sense if you have not been a desk jockey all your life, like a journalist, or an attorney...

Originally posted by Azp420
Why can't you have a professional discussion with anyone who has an opposing viewpoint?

We do not see anything sticking up above the wave of destruction.

Because of the obvious lack of professionalism in these statements. You're dodging the obvious errors in your statements to keep yourself from looking stupid when you make statements like : 7 didn't have a core, despite all literature disagreeing with you; or dodging 250C creep as described in the towers by Bazant; etc.

He then gives the equation for Fs as

Fs = (gamma)*(Kc/h)

where (Kc/h) is the kinetic energy of a single story divided by the inter-story height of that story.

gamma is estimated to be 0.7.

In Bazant's own words, he states the fraction of kinetic energy that is dissipated in each floor due to the work done by comminution is 0.7, or 70%.

Another lack of attention to detail.

Read it again. It is not a single story. It is a single slab. IOW, 70% would be accurate if a single slab was hitting a single slab. This is most definitely NOT an estimate of the KE from the entire descending upper block absorbed by a single floor.

Since that didn't happen, your objections are discarded as mere rantings from another truther trying to spin engineering to suit his/her predispositions.

Here's what he says in that paper about determining the coefficient for concrete breakage, showing that concrete breakage is a very small part of the totl KE absorbed.

"It must nevertheless be emphasized that calculations prove the velocity
of crush-down not to be very sensitive to the value of
. For all
2 [0.5, 1], the calculated z(t)
matches the video and seismic observations considered later quite well (although
< 0.6 would
not give a close match of the observed particle distribution)."

It does not prove the OS.

Only to truthers, it doesn't, for they live in denial of the fact that despite their objections about the "OS", nobody listening to them cares about their objections, and smoking guns, etc.

Same for you.

We want to know precisely what happened.

You ain't gonna get it.

Originally posted by Azp420

This 15 story mass (which is supposed to crush down on the rest of the tower then crush up on itself once it has finished doing that) disintegrates itself on many floors at once, BEFORE the wave of destruction begins to destroy the intact structure below the aircraft impact zone. Bazant's model is extremely inaccurate because it does not describe this happening or how this happens.

Do you actually believe your own statements? If so, then you are viewing this through your truther glasses, and not realistically.

The red line, that is supposed to represent the initiation point, is in the wrong spot. It needs to be higher. This has been debunked LONG AGO.

This is so 2006, it ain't funny.

Originally posted by Joey Canoli
The red line, that is supposed to represent the initiation point, is in the wrong spot. It needs to be higher. This has been debunked LONG AGO.

This is so 2006, it ain't funny.

LOL you're funny.

Move the red line up Joey, see if it makes any difference.



The red line isn't the issue, remove it all together if you wish it doesn't change what the top is doing.

Originally posted by Joey Canoli
You ain't gonna get it.

But Joey I thought we already had it?

Are you admitting the NIST report, or any other pro OS report, is not precisely what happened?

Very interesting statement you make and you sound so sure, how would you know and why do you care so much? If it happened as you claim then why would you worry about knowing 'precisely what happened'?

BTW I've been here since 04, who were you in 06? How many accounts have you had? I know a lot of debunkers have had many aliases, coming back around with the same arguments. Mostly from jref coincidentally.

[edit on 7/28/2010 by ANOK]

reply to post by Joey Canoli

Because of the obvious lack of professionalism in these statements. You're dodging the obvious errors in your statements to keep yourself from looking stupid when you make statements like : 7 didn't have a core, despite all literature disagreeing with you; or dodging 250C creep as described in the towers by Bazant; etc.

I said 7 had columns throughout, which it did, but that is hardly an important point to argue about and proves nothing. I also don't care to argue about about creep, there are far more important points to be made, please stop badgering me about the creep, I haven't looked into it and don't have the time. What happened after initiation is the obvious smoking gun. I have remained professional throughout this discussion. You on the other hand have continuously resorted to personal attacks, arguing semantics instead of the physics, quoting out of context and other dishonest tactics in your emotionally charged posts.

Read it again. It is not a single story. It is a single slab. IOW, 70% would be accurate if a single slab was hitting a single slab. This is most definitely NOT an estimate of the KE from the entire descending upper block absorbed by a single floor.

I know it is a single slab. Is there not one slab per story?

Since that didn't happen, your objections are discarded as mere rantings from another truther trying to spin engineering to suit his/her predispositions.

You have completely ignored the comments I made about the video you posted. Don't have a link to Bazant's work to explain it away? Seems my observation that you are unable to argue for yourself on the physics was accurate. This is a huge point I made so I will elaborate on it:

WTC1, WTC2 and WTC7 all did what none of the explosive-less demolished buildings did - accelerated at close to free fall through through the undamaged portions of their structures. Huge red flag right here for anyone that can see the implications. It is counter-intuitive to most people but I will do my best to explain.

The top portion of the structure (above the initiation zone) is the falling mass. For the falling mass to produce a force on the lower part of the structure which is larger than if it were stationary, the lower structure must decelerate the falling mass. If the lower structure does not decelerate the falling mass (the falling mass continues to accelerate at any rate between zero and free fall) then the falling mass is actually applying less force to the lower structure than if it were not moving (something else is getting the lower structure out of the way). This is the reason a normal structure cannot accelerate through itself. This is the reason all of the structures in the explosive-less demolition video performed as expected. The falling masses all decelerated into the lower structures, producing larger forces than if the top masses were stationary, overcoming the capacities of the lower portions.

Assuming a pancake collapse, in an unusual structure with extremely high inter-story heights you could have overall acceleration if the downwards acceleration gained between floors were greater than the deceleration as each floor impacted but again, there needs to be deceleration at some point (jolts at the impact of each floor). None of the WTC buildings had unusual inter-story heights, and significant decelerations cannot be observed at the impact of each floor.

I will explain my point more mathematically next post.

reply to post by Joey Canoli


In other words,

Before initiation the stationary top mass is producing a force equal to 1.0W on the bottom structure, where W is the weight of the top mass. The lower structure is holding up the top mass with an equal and opposite force of 1.0W, therefore the net force acting on the top mass is zero and we have no acceleration of the top mass, as F=ma.

After initiation there is a fairly constant acceleration of the top mass to the ground, lets say at 70% free fall (but any acceleration greater than zero proves the point, so it does not matter). Once the mass starts falling, what prevents it from reaching 100% free fall? Mainly the upwards force provided by the building. If the falling mass is accelerating at 70% free fall, the net force acting on the mass is 0.7W (a 1.0W net force produces free fall). The downwards gravity force acting on the mass is 1.0W, therefore the upwards building resistance force acting on the mass is 0.3W. So the lower portion of the structure is producing a force on the falling top mass of 0.3W.

Every action has an equal and opposite reaction.

Therefore if the lower structure is producing an upwards force of 0.3W on the falling mass, the falling mass is now only producing a downwards force of 0.3W on the lower structure.

0.3W < 1.0W, therefore the top mass is now producing a lower force in the bottom structure than when it was stationary. We must see some sort of deceleration force the falling mass to produce a force larger than 1.0W.

It is the reason no experiment has so far been able to replicate the behaviour of the collapse of the towers, and the reason the collapse propagation does not get much of a mention in the OS.

You ain't gonna get it.

At-least we know what didn't happen. I agree that we will probably never get the whole truth.

Do you actually believe your own statements? If so, then you are viewing this through your truther glasses, and not realistically.

The red line, that is supposed to represent the initiation point, is in the wrong spot. It needs to be higher. This has been debunked LONG AGO.

This is so 2006, it ain't funny.

Of-course I believe my statements, I have many years of engineering education as well as logic, physics and reasoning on my side to back them up. You calling me names does not make my statements less true.

Once again, the only 'argument' you manage to produce is an irrelevant copy-paste from Bazant and more of the same personal attacks and dirty tactics. This is the Physics of 9/11 thread, I have been presenting my argument with credible physics, yet you remain unable to do the same.

Like ANOK said, move the red line where ever you want or remove it completely. I watched a slow motion video of that gif without the red line before I made my comment.




[edit on 28-7-2010 by Azp420]

Originally posted by Azp420

I know it is a single slab. Is there not one slab per story?

Was the entire upper part descending, or just a single slab?

Once you admit the entire upper part was descending, you render your statement that 70% of the KE should be absorbed by every slab impacted to be a lie.

The top portion of the structure (above the initiation zone) is the falling mass.

Agreed.

For the falling mass to produce a force on the lower part of the structure which is larger than if it were stationary, the lower structure must decelerate the falling mass.

Not necessarily decelerate. It may also only have enough resistance capacity to slow the acceleration, but never actually decelerate it

This is an important point..

If the lower structure does not decelerate the falling mass (the falling mass continues to accelerate at any rate between zero and free fall) then the falling mass is actually applying less force to the lower structure than if it were not moving

Wrong again.

The lower structure can apply resistance that can be described as a deceleration vector, while gravity is applying the acceleration vector.

If the d.v. is less than the a.v., then there is STILL acceleration, but at less than freefall acceleration.

This is elementary physics.

This is the reason a normal structure cannot accelerate through itself.

Wrong. It absolutely can, and once you correct your views on the above error you will agree.

Any normal structure can accelerate through itself at less than ffa when the KE of the moving structure is more than the impact point can absorb. This will result in less than ffa.

This is the reason all of the structures in the explosive-less demolition video performed as expected. The falling masses all decelerated into the lower structures

Wrong again.

They accelerated at less than free fall into the lower structure. If they were to decelerate, they would stop. This is called a failed demolition, and has happened.

producing larger forces than if the top masses were stationary, overcoming the capacities of the lower portions.

Agreed.

significant decelerations cannot be observed at the impact of each floor.

Tony Szamboti thinks this too. Once again, I'll point out that truthers have found "jolts" that resulted in lesser acceleration, but still not deceleration.

the911forum.freeforums.org...

If you care to read that rather lengthy thread, you'll se what they have found for themselves, and that it renders your statement false.

Originally posted by Azp420
Before initiation the stationary top mass is producing a force equal to 1.0W on the bottom structure, where W is the weight of the top mass. The lower structure is holding up the top mass with an equal and opposite force of 1.0W, therefore the net force acting on the top mass is zero and we have no acceleration of the top mass, as F=ma.

Agreed. But keep in mind that the upper structure has a PE state of 1.0W. This is important for you to learn, so that you may correct your misunderstanding.

After initiation there is a fairly constant acceleration of the top mass to the ground, lets say at 70% free fall

Agreed.

(but any acceleration greater than zero proves the point, so it does not matter).

Yes, it proves the point that the lower structure did not have the capacity to decelerate the moving structure.

It proves that it only had enough KE absorption capacity to keep the acceleration at 70% of ffa.

Once the mass starts falling, what prevents it from reaching 100% free fall? Mainly the upwards force provided by the building.

I'd say resistance to KE, not upwards force. But ok.

If the falling mass is accelerating at 70% free fall, the net force acting on the mass is 0.7W (a 1.0W net force produces free fall). The downwards gravity force acting on the mass is 1.0W, therefore the upwards building resistance force acting on the mass is 0.3W. So the lower portion of the structure is producing a force on the falling top mass of 0.3W.

Completely wrong.

The lower structure is providing 1.0W of upwards force at all times. It does not need to change for the enrgy balance to be correct and acquire 70% ffa..

Since the upper structure is now moving, it no longer is producing 1.0W of force downwards. It HAS changed its energy state from PE to KE. Once it starts moving, the 1.0W of PE is converted into another form, KE, and velocity gives it 1.7W of energy.

You cannot deny that a moving object has a higher energy state than a stationary one. This is key for you to understand the energy balance between the 2 parts of the structure.

The lower structure hasn't changed, and can absorb 1.0W of KE. But the upper, moving part has 1,7W of KE. That leaves 0.7W to accelerate the mass.

This results in acceleration of 70% of ffa.

Every action has an equal and opposite reaction.

Only in a closed system.

Therefore if the lower structure is producing an upwards force of 0.3W on the falling mass,

It wasn't.

the falling mass is now only producing a downwards force of 0.3W on the lower structure.

Abysmally wrong, on many levels.

0.3W < 1.0W, therefore the top mass is now producing a lower force in the bottom structure than when it was stationary.

Wrong again.

the lower structure could absorb 1.0W of KE, but the upper moving mass was producing 1.7Wof KE.

Its energy state has changed from 1.0W of PE into 1.7W of KE.

Again, this is elementary physics.

It is beyond merely ludicrous to suggest the a moving body is in the same energy state as it was when it was stationary. It borders on irrational.

the reason the collapse propagation does not get much of a mention in the OS.

If you mean NIST, then as I've stated before, it's because it's not necessary to reproduce it to the rational. We understand the physics that you do not, as displayed in your post here.

You have no grasp at all.

You make the same elementary mistakes/misleading statements as David Chandler. Frank Greening had an email exchange with him, where he pointed out his charlatan ways/poor education:

the911forum.freeforums.org...

"First of all, Chandler measures a uniform downward acceleration of 6.31 m/s^2 for the upper block of WTC 1 and correctly states that this is equal to 64 % of g. From this observation Chandler concludes that during the collapse of WTC 1 there was an upward, resistive force of 36 % of W, where W is the weight of the falling section of the building.

At this point in his presentation Chandler gives a diagram of the upper block showing a force W acting downwards together with a force equal to 0.36W acting upwards. This diagram therefore correctly indicates that there was a net downward force of 0.64W acting on the upper block.

I would say that this diagram should have ended Chandler’s presentation but instead he now pulls a sleight of hand by showing a new diagram of the upper block resting on the lower section of WTC 1 with a force of 0.36W acting upwards (ok!), AND a force of 0.36W acting downwards, (not ok!). I say this downward force is not ok because Chandler has already shown that the downward force was W, not 0.36W. The net force of 0.64W explains why the upper section was accelerating relative to the lower, immovable section at 64 % of g.

But let’s be very clear on this one point: if Chandler’s new diagram correctly represented the forces acting inside WTC 1 during its collapse, the upper section would not have been capable of motion relative to the lower section since there would have been no net force acting between the sections. This, of course, is the situation in a stable, undamaged building. However, WTC 1 was not stable but quite severely damaged! Furthermore, only if the entire building was accelerating at 36 % of g, (somewhere in outer space perhaps!), would the forces between the upper and lower sections be 0.36W.

I think Chandler’s confusion, (or deliberate obfuscation!) arises from the fact that he is only considering forces acting within a tower where no parts are moving relative to one another. "



So, are you in fact David Chandler, or merely love his flavor of koolaid?


Or Frank Legge?

Posted by Hambone: (site owner Greg Urich)

"A member at STJ911 used a similar line of argument (based on not understanding basic physics)with me regarding the conservation of momentum. I suggested that this member check with Tony Szamboti, Greg Jenkins or Frank Legge (all members) whom I assumed could help explain. To my amusement I found out that the member WAS Frank Legge."

[edit on 29-7-2010 by Joey Canoli]

[edit on 29-7-2010 by Joey Canoli]

[edit on 29-7-2010 by Joey Canoli]

reply to post by Joey Canoli

Any normal structure can accelerate through itself at less than ffa when the KE of the moving structure is more than the impact point can absorb. This will result in less than ffa.

How come we didn't see that in any of the example structures in the video you posted? You are wrong, as I will explain mathematically.

They accelerated at less than free fall into the lower structure. If they were to decelerate, they would stop. This is called a failed demolition, and has happened.

I'm not sure you understand the concept of acceleration. None of the structures in the video achieved a higher velocity than right before the upper impacted the lower. They decelerated, but that doesn't mean they had to stop before they reached the ground. Why do you say they would stop? They simply decelerate at a rate which doesn't have them stopping before complete demolition. I didn't put a value on the rate of deceleration.

Agreed. But keep in mind that the upper structure has a PE state of 1.0W. This is important for you to learn, so that you may correct your misunderstanding.

Your post gets quite comical from here. I'm still trying to work out if it is a deliberate tactic and you are pretending to miss the entire point or misrepresent the entire point (to avoid having to debate the equations) or if you genuinely are that confused about the equations I produced.

You seem to have gone off on this big tangent about energy. I clearly defined W as the weight of the top section (you later appear to start confusing it with the unit for watts or something). Weight is different to mass and is different to energy. Weight is a force.

I'd say resistance to KE, not upwards force. But ok.

This is a classic quote. It seems you are a bit confused about the concept of force equilibrium and how forces relate to energy. To help your understanding I'll give you an example of a skydiver.

A skydiver experiences resistance to his KE via air resistance which has him accelerate at less than free fall. The air resistance is an upwards force acting on him, just as gravity is a downwards force acting on him. Throughout his dive, gravity is producing a constant downwards force on the skydiver of 1.0W, where W is the WEIGHT of the skydiver. Air resistance is different to structural resistance because the higher the skydivers velocity, the more resistance is provided (proportional to velocity squared). So unlike in a structure, the air provides no resistance when the skydiver is not moving. This means the initial net force on the skydiver is 1.0W downwards (1.0W from gravity minus 0.0W from air resistance). So the skydiver initially accelerates at free fall. The faster he goes, the more air resistance he experiences, therefore his rate of acceleration drops. At some point in his jump the net force on him is 0.5W downwards (1.0W downwards from gravity minus 0.5W upwards from air resistance). At this point he is accelerating at 50% free fall. Later in the jump the skydiver reaches terminal velocity (no acceleration or 0% free fall). For there to be no acceleration the net force acting on him is 0.0W (1.0W downwards from gravity minus 1.0W upwards from air resistance). Are you with me so far Joey? Do you need me to go into more depth as to how I arrived at any of these numbers or do you dispute any of them?

The lower structure is providing 1.0W of upwards force at all times.

Incorrect. The force produced by the lower section which acts on the top section is equal and opposite to the force produced by the top section acting on the lower section. If it did provide a 1.0W upwards force at all times, we would have a net force of 0.0W acting on the top section (1.0W downwards gravitational force minus 1.0W upwards lower structure support force).

(continued next post)

[edit on 29-7-2010 by Azp420]

reply to post by Joey Canoli


This is only true when the top mass is stationary. For there to be an acceleration, there MUST be an imbalance of forces (some net force). This is an indisputable fact. Another indisputable fact is that the force due to gravity (the 1.0W downwards) remains constant at all times. So how can we have an acceleration? The only other significant force acting on the top mass in the vertical direction is the upwards force provided by the lower structure (which is initially holding the top mass up with an equal and opposite force of 1.0W).

As the initiation zone gives way, the lower structure is now producing less than 1.0W of upwards force in the top section, resulting in a net downwards force acting on the top section. If the top section is accelerating at 70% free fall, the net force acting on the top section is 0.7W (1.0W downwards gravitational force minus 0.3W upwards lower structure resistance force). Remember, for there to be an acceleration there has to be an imbalance of forces, the gravitational force is constant, and the only other significant vertical direction force is the upwards structural resistance. 0.3W upwards is less than 1.0W upwards but we can explain this by assuming that after jet impacts and fires once the columns etc started to buckle the largest upwards resistance force the initiation zone was able to act on the upper section was now only 0.3W instead of 1.0W. Fair enough so far (I've not really looked into the validity of the OS version of initiation but the events so far are plausible enough from this force-acceleration point of view).

After the falling top section meets the undamaged bottom section is where things get interesting. It is understandable and logical that the heavily damaged initiation zone buckles and only produces an upwards force acting on the top section which is less than 1.0W but not in the undamaged lower structure. Once the top section impacts the lower section one would expect deceleration to occur because the lower structure should have been able to produce an upwards force acting on the upper section of 1.0W or greater. If it was 1.0W upwards, then the net force on the upper section would have been zero, and neither acceleration nor deceleration would have occurred. If it was greater than 1.0W (which it should have been easily capable of) then the net force is upwards and deceleration would occur, as expected. This was not the case however. It was measured that the falling top section continued to accelerate. For the top section to continue to accelerate there MUST be an imbalance of forces acting on it, so lets take a look at what we know and what is unknown at this point, then try to balance the equation.

Downwards forces acting on the top section:
Gravitational, with a magnitude of 1.0W (W was defined earlier)

Upwards forces acting on the top section:
Upwards resistance force provided by lower structure, magnitude unknown at this point.

To obtain that unknown we need the acceleration of the falling top section, which has been measured by various people using various methods. I will continue to use the value of 70% free fall suggested by Joey in a previous post, but like I said earlier, the exact value does not matter as any value between zero and free fall would prove my point.

Recall when the skydiver was at 50% free fall acceleration, the net downwards force acting on him was 0.5 of his W. Similarly, for the falling top section, the only way for it to be at 70% free fall is if the net downwards force acting on it is 0.7W. Since there are only two components to this net force (downwards gravity minus upwards structural resistance) and one of them is known, we now can calculate the remaining unknown force.

0.7W = 1.0W - x

x = 0.3W

So the lower structure has gone from providing an upwards force of 1.0W to only 0.3W.


(continued next post)...

reply to post by Joey Canoli


I will leave everybody to ponder the implications of my last statement on their own.

Hopefully now Joey, you can see how each of the values I used are derived. Feel free to point out any specific errors you think I have made and I will explain in more detail or produce more detailed calculations as how how the values are derived. I am not interested in a copy-paste or link to an irrelevant section of Bazant's work. This is the Physics of 9/11 thread, debate me yourself on this high school level mechanics derivation. I'm not talking about energy, so please don't begin to confuse this derivation with energy again.

You cannot deny that a moving object has a higher energy state than a stationary one. This is key for you to understand the energy balance between the 2 parts of the structure.

In the case of the falling top mass, which is what you are discussing in the context of this quote, it is actually in an equal energy state when it is moving to when it is stationary. Energy is not created or destroyed, just converted from one form to another. The gravitational potential energy is merely converted into kinetic energy, no net change in the overall energy state.

Only in a closed system.

Your post seems like one big confusion of physical laws and concepts.

Since the upper structure is now moving, it no longer is producing 1.0W of force downwards. It HAS changed its energy state from PE to KE. Once it starts moving, the 1.0W of PE is converted into another form, KE, and velocity gives it 1.7W of energy.

Quoted for comedy. You began the paragraph talking about force and ended talking about energy. You sound like someone trying to talk intelligently about something which is right on the edge of his understanding, and failing. Do you want to tell us how you arrived at the value of 1.7W of kinetic energy? You mentioned velocity. The formula for kinetic energy is
Ke = 0.5*m*v^2
What value for velocity have you used to produce your 1.7W of kinetic energy? As soon as it has a velocity greater than zero? When it is at its maximum velocity? No wonder you have been heavily reliant on directing people to Bazant's work.

So, are you in fact David Chandler, or merely love his flavor of koolaid?

I am not David Chandler, although he has done some great work for AE911truth. I would ask if you were Bazant but it is obvious you lack the physics and structural understanding to produce such a paper. You are merely one of his fanboys.

Or Frank Legge?

Not Frank Legge either. Discrediting is your main tactic then, seeing as you can't argue for yourself on the physics? Hopefully we can get a half intelligent critique of my derivation out of you in your next post and not more dirty tactics and copy-pastes. You also have the audacity to tell me, who does this for a living, what I need to learn, when you are clearly in over your head discussing basic mechanics.

Edit: (I wanted to edit this into my first post where I used this quote but I've run out of characters)

I'd say resistance to KE, not upwards force. But ok.

I feel I should point out for your understanding that in physics when discussing mechanics, resistance is always a force.



[edit on 29-7-2010 by Azp420]

Originally posted by Azp420
If it did provide a 1.0W upwards force at all times

It does.

we would have a net force of 0.0W acting on the top section (1.0W downwards gravitational force minus 1.0W upwards lower structure support force).

Wrong.

The lower part pushes up at all times at 1.0W

The upper part, when the structure is intact and not moving, pushes down at 1.0W.

However, once columns buckle and the upper part attains motion, it pushes down at 1.7W.