9/11

[PolyNewbie]

People who believe official version of 9/11 are crazy

Various doctors listed with hyperlinks,

On a slightly different topic, here is a link leading to various structural engineers, physics Phd's, etc that say the same thing.

PatriotsQuestion911

[buffycat]

It's Riverwind's example, and it's a massive simplification, but it does work to some extent. What it shows, however, is that Riverwind is wrong.

You are right. Tables don't fall straight down unless the strenght of each and all the legs is overcome all together in perfect balance.

Indeed, exactly what I thought as I recalled my first year physics.

[kuzadd]

I'm having a hard time following the table example - it seems to me that it is only relevant if one has a one-legged table.

If there are four legs, then the mass of the table and the force of gravity acting upon it will distribute the weight evenly over all four legs (or three - if you like).

Now, unless ALL four legs fail in the same manner at the same time, there is a very good chance that the table top will not fall straight down (ie evenly over the 'footprint' of its four (or three) legs).

Have you not seen tables collapse? I have. And they don't all fall straight down.

I think this comparison is not workable.

It's Riverwind's example, and it's a massive simplification, but it does work to some extent. What it shows, however, is that Riverwind is wrong.

You are right. Tables don't fall straight down unless the strenght of each and all the legs is overcome all together in perfect balance.

Riverwind unfortunately and despite his/her numerous cheerleaders, has been wrong more then once, already.

[PolyNewbie]

Riverwind unfortunately and despite his/her numerous cheerleaders, has been wrong more then once, already.

Actually, Riverwind has never been correct about a single one of his voluntary scientific statements, despite all of his insults and arrogance. He has been 100 % wrong in every single scientific statement he has made on this thread and other threads wrt 9/11.

[guyser]

I checked the poll.

There is not a "none of the above" boxes to check. I wonder why.......

[Figleaf]

Speaking of science, I just did a little experiment to understand the table example better. I'll describe it...

Materials:

scotch invisible tape

four wooden matches

four dimes, different mint years.

22 (almost) identical 6hr VHS tapes

Method:

1. Clip lucifer heads off the matchsticks.

2. Use tape to affix matchsticks near the corners of one VHS tape to create a table-like structure with legs of equal length.

3. Use additional tape to reinforce three legs. Mark fourth (weak) leg.

4. Place 'table' on floor.

5. Place dimes on top of 'table' near each corner, dated side up.

6. Record date of each dime to match each corner. (QV diagrams).

7. Set all VHS tapes to midpoint of tape play-time.

8. Add VHS tapes to top of 'table', one by one, until table falls.

9. Observe eventual collapse and record location of dimes.

Results:

1. The table fell at 11 videotapes.

2. The fall occurred to quickly to observe with certainty.

3. On investigation, two 'legs' were broken: the 'weak leg', and the other leg on the long side (q.v. diagrams).

4. Two legs remained intact. The location of the dimes was recorded. (per diagrams (q.v.).

The table did not fall symetrically despite symmetrical placesmnet of load.

[Riverwind]

You are right. Tables don't fall straight down unless the strenght of each and all the legs is overcome all together in perfect balance.

Let's try this again:

We have a table with 4 ridgid legs that can only support 4000N of force. These legs _will_ collapse if exposed to more than that amount of force. They will not bend over or otherwise do any of the things that you claim. That is the assumption that my example is based on. You cannot explain away my example by ignoring the assumptions I started with.

This scenario starts when Leg 1 is damage by an external force and collapses. The load redistributes to the other legs. The exact distribution of the load could very but we can assume that legs 2 & 3 would support much of the load. This would mean they would support 5000N which exceeds their capacity which causes them to collapse.

At this point the load will redistribute again to the remaining leg. This puts 10000N force on leg that can only support 4000N. This will cause that leg to collapse immediately. The table top cannot rotate unless the leg stays standing long enough to allow the table top to gain significant rotational momentum. This is simple physics - a body cannot start moving unless a force is acting on it. In this case, the table top cannot start rotating because there is no force acting on it since the last table leg collapsed immediately.

Try thinking about what would happen if the table legs were near the center of the table (i.e. like the main support columns in the WTC towers). In this situation there would be very little torque produced because leg 4 would be close to the center of mass. It should be obvious that the table would not rotate: it would collapse straight down because the leg cannot support the weight.

[Riverwind]

The table did not fall symetrically despite symmetrical placesmnet of load.

I am not claiming that every table would fall straight down - I am simply saying that some structures can collapse straight down after asymmetrical damage. So your experiment does not provide any information that contradicts my example.

[jbg]

Trying to beat the record of the original PN 911 thread?

[PolyNewbie]

I am not claiming that every table would fall straight down - I am simply saying that some structures can collapse straight down after asymmetrical damage. So your experiment does not provide any information that contradicts my example.

On the amount of time you have spent on these threads you could have picked up a grade thirteen text on physics, self studied the section on mechanics and maybe learned something so that you would actually know what you are talking about.

Right now you are not fooling anyone. If I could I would bill you for my time having to read your nonsense.

Riverwind:Try thinking about what would happen if the table legs were near the center of the table (i.e. like the main support columns in the WTC towers). In this situation there would be very little torque produced because leg 4 would be close to the center of mass. It should be obvious that the table would not rotate: it would collapse straight down because the leg cannot support the weight.

The center support would buckle - the solution for buckling falls comes from the PDE solution of a vertical column that is loaded. You would know this for sure if you were really an engineer. The support would bend.

jbg:Trying to beat the record of the original PN 911 thread?

I'm hoping you have something intelligent to say this time.

[PolyNewbie]

"Those who can make you believe absurdities can make you commit atrocities" - Voltaire

[Riverwind]

The center support would buckle - the solution for buckling falls comes from the PDE solution of a vertical column that is loaded.

To are confusing the mechanism of leg failure with what happens to the table top after failure. The leg fails quickly - how it fails depends on the material. It could shatter or crumple like an aluminum can - the exact mechanism does not make a difference. If the leg fails it cannot extert a force on the table top that would cause it to rotate.

Try putting a book on top of peice of spaghetti. The book would collapse straight down after the spaghetti bends and shatters. You are deluding yourself if you think that a collapsing leg would always cause the table to tip.

[Figleaf]

You are right. Tables don't fall straight down unless the strenght of each and all the legs is overcome all together in perfect balance.

Let's try this again:

We have a table with 4 ridgid legs that can only support 4000N of force. These legs _will_ collapse if exposed to more than that amount of force. They will not bend over or otherwise do any of the things that you claim. That is the assumption that my example is based on. You cannot explain away my example by ignoring the assumptions I started with.

But you can't prove anything with an 'example' that bears little connection to the real world. Anyone can prove whatever they like with an example where the laws of physics are whatever they decide.

This scenario starts when Leg 1 is damage by an external force and collapses. The load redistributes to the other legs.

You need to take into account the center of gravity to determine whether/how the load redistributes.

The exact distribution of the load could very but we can assume that legs 2 & 3 would support much of the load. This would mean they would support 5000N which exceeds their capacity which causes them to collapse.

At this point the load will redistribute again to the remaining leg. This puts 10000N force on leg that can only support 4000N. This will cause that leg to collapse immediately.

Well, so far you haven't added anything that hasn't already been discussed. Your example here has legs 2 and 3 breaking first. The center of gravity of the top lies directy between 2 and 3 and gravity will begin drawing it downward the instant 2&3 give. As PN says, this force creates a bending force on Leg 4 and the table top, not simply a direct downward force.

Do this for yourself -- take any L shaped object, turn it upside down so the short limb is horizontal and the long limb points down. Affix the bottom of the long leg to something. Now push down on the exact midpoint of the short limb. See what happens.

The table top cannot rotate unless the leg stays standing long enough to allow the table top to gain significant rotational momentum.

Again, any length of time will impart some rotation.

This is simple physics - a body cannot start moving unless a force is acting on it. In this case, the table top cannot start rotating because there is no force acting on it since the last table leg collapsed immediately.

1. It begins to collapse AFTER 2 and 3.

2. There is force acting on it. The force of gravity, which 'simple physics' tells us acts wrt the object's center of gravity, i.e. about halfway out in the middle of the tabletop.

3. Even if, magically, the fourth leg collapsed straight down, the resistance of as-yet-intact portions of that leg would supply greater resistance than the air under and to the far side of the table top. For your magical straight downward collapse to continue (presuming simly for the sake of argument it could even begin, which it couldn't) you need to somehow vaporize (as the explosives do in a demolition) the whole of leg 4 to sustain the straight downward fall.

Try thinking about what would happen if the table legs were near the center of the table (i.e. like the main support columns in the WTC towers). In this situation there would be very little torque produced because leg 4 would be close to the center of mass. It should be obvious that the table would not rotate: it would collapse straight down because the leg cannot support the weight.

Well, now you're changing the example quite a lot. This new scenario is a very special and narrowly applicable hypothetical case which does not capture the nature of the WTC structures.

IF there were a single, perfectly centred support (completely unlike the WTC buildings) it would still have to be overcome with a perfectly symmetrical force to collapse directly downward. And as per point 3 above, the damage to the support would have to STAY symmetrical throughout the whole collapse, despite the virtual certainty of chaotic results of fracturing in the material.

[Figleaf]

The table did not fall symetrically despite symmetrical placesmnet of load.

I am not claiming that every table would fall straight down - I am simply saying that some structures can collapse straight down after asymmetrical damage. So your experiment does not provide any information that contradicts my example.

You've shifted ground, attempting to defend your example by reference to the buildings. Certainly my experiment doesn't tell us all there is to know about the buildings. But it definitely does directly contradict your example.

Try putting a book on top of peice of spaghetti. The book would collapse straight down after the spaghetti bends and shatters.

If the spagetti BENDS the book will fall assymetrically. IF the spagetti crumbles AND continues to crumble, uniformly, the whole way down, then yes, the book falls directly downward. But the WTC buildings were not supported by a single uniform centre column.

[GostHacked]

The center support would buckle - the solution for buckling falls comes from the PDE solution of a vertical column that is loaded.

To are confusing the mechanism of leg failure with what happens to the table top after failure. The leg fails quickly - how it fails depends on the material. It could shatter or crumple like an aluminum can - the exact mechanism does not make a difference. If the leg fails it cannot extert a force on the table top that would cause it to rotate.

Try putting a book on top of peice of spaghetti. The book would collapse straight down after the spaghetti bends and shatters. You are deluding yourself if you think that a collapsing leg would always cause the table to tip.

Try it then. If there spagetti turns to dust and breaks into very small almost unified peices ... the you are correct.

I think the problem is in how everyone approaches the leg or beam. This table needs some moidifcation now and we need to expand this model

This square table now had a hard solid post in the middle of the table. This post is bigger than the 4 corner posts combined.

Wait what??? Top down force would make it bend and shatter? So bending occurs and (i am no freaking engineer here in any way shape or form) rotation would occur as well??

[PolyNewbie]

Riverwind:To are confusing the mechanism of leg failure with what happens to the table top after failure.

I am not confusing anything. You are an incompetent liar and you are here to waste everyones time to nurse your own ego.

Riverwind:You are deluding yourself if you think that a collapsing leg would always cause the table to tip.

You are deluding yourself and everyone that participates in this and other threads when you start portraying yourself as an engineer when you are not. You have stated that you are an engineer and have implied that people should take your word based on that and your arrogance.

No, exactly what kind of engineer are you ?

[stignasty]

Of course, what you're all neglecting is that World Trade Center buildings 1, 2 and 7 were all occupied office buildings and no one can offer any evidence that there were any explosives wired into any of the buildings. Sure, there are the stories of mysterious sounds on vacant floors or dust, but nothing that actually says, "I saw explosives wired into the buildings," or "I saw rolls of detonator cables being brought into the towers."

Because of this, any talk of controlled demolition is purely supposition and not the "proof" the so called "truth" movement would like us to believe. Bottom line: show me evidence that there were explosives.

Finally, this is what a controlled demolition of a building looks like. http://www.controlled-demolition.com/image...nt/jlhudson.mpg Notice that there are visible flashes from the explosions. Notice how no material is being fired out of the building into surrounding structures. Notice how the building is not wrapped with material. Notice how the building falls into itself and not onto surrounding structures. The way the buildings fell on 9/11 was nothing like this.

So, as far as I am concerned, this case is closed.

[Riverwind]

Again, any length of time will impart some rotation.

I agree. There would always be some rotation. The issue is how much rotation. You cannot claim that this rotation will always be large enough to cause the table top to tip before it hits the ground.

You are missing a basic principle of physics: the speed of an object depends on the magnitude force applied AND the time the force was applied. If the force was applied for a short time then the speed will be small. In my example, the leg collapses quickly which means any rotational momentum would be insignificant compared to downward momentum. This means the table will not tip before it hits the ground. You could argue that it would eventually tip if it fell into an infinitely deep pit but that is not a particularily useful observation.

This discussion is moot. On 9/11 we saw three buildings collapse straight down as a result of asymmetric damage. That is more than enough evidence to demonstrate that my hypothesis is plausible. (My hypothesis is that it is possible for certain kinds of structures to collapse straight down after asymmetric damage).

[Riverwind]

Try it then. If there spagetti turns to dust and breaks into very small almost unified peices ... the you are correct.

The spaghetti could bend and snap in two peices and the book would still fall straight down. A peice of spaghetti cannot extert enough force to cause a book to rotate 'significantly'.

Wait what??? Top down force would make it bend and shatter? So bending occurs and (i am no freaking engineer here in any way shape or form) rotation would occur as well??

The issue is how _much_ rotation. I am arguing that it takes time to cause something to rotate and that there would not be enough time to cause enough rotation. Imagine a toy car on a flat table - pushing that car with a force for 2 seconds will make it go faster than the same force for one second. A table leg that stays standing for 10 seconds would likely cause the table to tip. A table leg that collapses/bends/snaps after 1/2 second would not necessarily cause any significant tipping.

[GostHacked]

Of course, what you're all neglecting is that World Trade Center buildings 1, 2 and 7 were all occupied office buildings and no one can offer any evidence that there were any explosives wired into any of the buildings. Sure, there are the stories of mysterious sounds on vacant floors or dust, but nothing that actually says, "I saw explosives wired into the buildings," or "I saw rolls of detonator cables being brought into the towers."

Because of this, any talk of controlled demolition is purely supposition and not the "proof" the so called "truth" movement would like us to believe. Bottom line: show me evidence that there were explosives.

Finally, this is what a controlled demolition of a building looks like. http://www.controlled-demolition.com/image...nt/jlhudson.mpg Notice that there are visible flashes from the explosions. Notice how no material is being fired out of the building into surrounding structures. Notice how the building is not wrapped with material. Notice how the building falls into itself and not onto surrounding structures. The way the buildings fell on 9/11 was nothing like this.

So, as far as I am concerned, this case is closed.

1 and 2 kind of flowered out and banana peeled when I look at it. HOWEVER. 7 came straight down. This one looks more like a controlled demo than 1 and 2... I sad LOOKS MORE LIKE ... It is very uniform. Compared to the damage 1 and 2 made to the surrounding buildings (including 7 they say to the one side of the building) 7 did not do much damage to it's surrouding building. And yet they had to take down or demo the rest of 5 and 6 I beleive. 4 and 3 were just demolished from the debris of 1 and 2.

I am not saying it is impossible but the probability of 1 and 2 going down, taking 7 with it later (straight down) and not taking 5 and 6 out, or any other building in the area is a puzzle to me.

http://www.buildthememorial.org/images/con...ilder/13543.jpg

No building outside the WTC leased property fell that day, or since. A couple of the near buildings are condemned for the time being, Like Deutsch Bank.

7 was damaged severly assymetricly. From official reports. Debris from one and two hit 7 near the bottom floors. So taking out some of the colums on that face should make the building collapse straigt down? Path of least resistance?? 7 Had a unique and reinforced structure due to being over a power substation. Why did the building just not fall into the hole?? OK ok .. i know.

http://oceanmirage.homestead.com/files/wtc7damage.jpg

Sure, there are the stories of mysterious sounds on vacant floors or dust, but nothing that actually says, "I saw explosives wired into the buildings," or "I saw rolls of detonator cables being brought into the towers."

No one ever saw the Grassy Knoll Shooter as well. But they heard it. Never discount aural testimony. Not that this example holds any water to some of you.

Finally, this is what a controlled demolition of a building looks like.

http://www.controlled-demolition.com/image...nt/jlhudson.mpg

Notice that there are visible flashes from the explosions. Notice how no material is being fired out of the building into surrounding structures.

Note that the buiding has been gutted and prepped for a controlled progressive collapse.

Notice how the building is not wrapped with material.

Notice that there are no windows, doors, ect.

Notice how the building falls into itself and not onto surrounding structures. The way the buildings fell on 9/11 was nothing like this.

Notice how you still have the volumetric flow of dust and other debris.

Let's look at 7 again.

http://911research.wtc7.net/wtc/evidence/p...aerial_wtc7.jpg

Notice the foot print it fell on. I am not saying it has to be an accurate controlled demolition. Or even a large scale demolition. Look at how little damage is done to the surrounding buildings compared to when 1 and 2 fell.

We are essentially looking and a two controlled explosions and a controlled implossion.

[Figleaf]

Again, any length of time will impart some rotation.

I agree. There would always be some rotation. The issue is how much rotation. You cannot claim that this rotation will always be large enough to cause the table top to tip before it hits the ground.

Um... rotation IS tipping.

You are missing a basic principle of physics: the speed of an object depends on the magnitude force applied AND the time the force was applied.

Actually, no. I'm relying on that, not missing it.

If the force was applied for a short time then the speed will be small. In my example, the leg collapses quickly which means any rotational momentum would be insignificant compared to downward momentum. This means the table will not tip before it hits the ground.

1. Maybe I don't understand what you're trying to say. Do you accept that one edge (or corner) of the tabletop will hit the ground before the other?

2. Do you accept that your explanation requires the entire final support to collapse catastrophically from top to bottom, faster that the accelleration of gravity?

This discussion is moot. On 9/11 we saw three buildings collapse straight down as a result of asymmetric damage.

Actually, WHETHER that is what we saw IS the very question under discussion. Reasserting your earlier assertion doesn't demonstrate any mootness.

Anyway, you have misstated the official explanation tendered for the collapse of WTC1 and WTC2. The official explanation is that intense heat weakened the steel. Even so, it is diffcult to imagine how the distribution of jet fuel could have been sufficiently uniform to create a symetrical collapse such as we all saw on TV.

And meanwhile, the flying shards that are officially credited with knocking WTC7 down (amazingly some time after they struck) struck only one side of the building and didn't carry jet fuel.

+++++++++++++++++++++++

Hey PolyNewbie -- is there any thinking out there about the possibility that flight 93 was meant for WTC7?

[GostHacked]

Anyway, you have misstated the official explanation tendered for the collapse of WTC1 and WTC2. The official explanation is that intense heat weakened the steel. Even so, it is diffcult to imagine how the distribution of jet fuel could have been sufficiently uniform to create a symetrical collapse such as we all saw on TV.

I think this is very interesting. Not enough fuel for a uniform symetrical collapse. If anything this may accelerate a non uniform collapse. The side that is structuraly compromised should start collapsing first. And since most of the fuel burned up in the initial fireball when the plane hit, I do not think there is enough fuel for even this scenario.

Again I am no engineer. And I have learned a few things from this thread about physics.

[Riverwind]

1. Maybe I don't understand what you're trying to say. Do you accept that one edge (or corner) of the tabletop will hit the ground before the other?

One edge would most likely hit the ground first - but that does not mean the load on the would fall off. The straight down motion would be the dominant motion and the table top would collapse into its footprint.

2. Do you accept that your explanation requires the entire final support to collapse catastrophically from top to bottom, faster that the accelleration of gravity?

No it does not - the leg could fail in many different ways from a total collapse to a single break. Once the table starts moving the momentum would be large enough that any leftover bits of the leg would be crushed or pushed aside. These leftover bits could affect the motion of the table top, however, this would be counter balanced by the leftovers from the other 3 legs. You cannot claim that the table would never collapse into its footprint.

Anyway, you have misstated the official explanation tendered for the collapse of WTC1 and WTC2. The official explanation is that intense heat weakened the steel.

Trying reading the NIST report. WTC 1 & 2 collapsed becuase the fires weakened the floor trusses connecting the inner columns to the outer columns. This caused the floors to sag which, in turn, pulled the outer columns inward. This triggered the collapse of the outer columns.

Imagine an aluminium can with no dents supporting a weight - dent the side and the can will collapse. Bending the outer columns weakened them. Once the building started moving the inner columns collapsed because they were only designed to support a static load.

[GostHacked]

Imagine an aluminium can with no dents supporting a weight - dent the side and the can will collapse. Bending the outer columns weakened them. Once the building started moving the inner columns collapsed because they were only designed to support a static load.

Experiment time.

Get an empty can. Pop can, whatever. Put weight on it. I recall doing this as a kid. Putting my foot on a pop can, lending some weight, and then with two hands tap the opposite sides of the can and the can squished on itself. Straight down. Most of the time when I did not time it right at the same time. I fell over.

[Riverwind]

Actually, WHETHER that is what we saw IS the very question under discussion. Reasserting your earlier assertion doesn't demonstrate any mootness.

The overwhelming weight of circumstantial evidence supports the widely accepted explanation for the collapses. This strongly suggests that symmetric collapses of towers are not improbable events and that we should try to understand why. I started off believing that something was suspicious but changed my mind when I thought about it and read the thoughts of different structural engineers and the NIST report.