Why do you still believe that a collapse due to fire wouldn't be possible?

[T.A.M.]

all the defense is here, and here, and here of http://911research.wtc7.net.

"Twin Towers' Rates of Fall Proves It Wasn't Fire (link)

Each of the Twin Towers fell completely in intervals of time similar to that taken for a block of wood dropped from a tower's roof to reach the ground. A block of wood has about the same average density as the main components of the towers near their tops.

In a vacuum, a block of wood (or lead) would take 9.2 seconds to fall from the tower's roof. In the air a block of wood, say ten inches on a side, might take 50 percent longer than in a vacuum. Fifteen seconds, a good estimate for the total time of collapse of the North Tower, is about the time it would take our block to fall from the roof. The rubble from the Tower probably had similar average density to our block of wood, since the floor slabs consisted of corrugated sheet metal and lightweight concrete, and the perimeter steel columns were hollow with walls only 1/4th inch thick at the Towers' tops. Air resistance alone could account for the slowing of the falls to the point where each Tower took about 15 seconds to completely come down.

The official story requires that more than air resistance was slowing the descents. The falling rubble would be having to crush every story below the crash zone -- ripping apart the steel grids of the outer walls and obliterating the steel lattice of the core structure. The resistance of the intact building itself would be thousands of times greater than air resistance.

If air resistance is able to increase total collapse times by even 20 percent, then shouldn't the addition of the resistance of the buildings themselves increase the time several thousand percent, to at least tens of minutes?"

Hopefully ^this isn't considered "a large amount of material"

In any case, at the exact time in which free-fall happened there should of been more resistance ie. no free-fall at that particular time.

15 seconds is about 65% more then 9.2 seconds. So you are saying air resistance alone would slow down steel beams and concrete by 65%? What do you base this on?

The fact that you think that the resistance of a single floor should slow things down at all means you have NO CONCEPT of momentum.

You are the weakest link, goodbye.

TAM

 

[Lenbrazil]

Exactly how are you calculating that or would you like to check with Hoffman on this?

Hoffman of course provides no substantiation for his claim about how much time air resistance would add given his propensity for screwing up basic math his claim is worthless.

 

[T.A.M.]

Hoffman of course provides no substantiation for his claim about how much time air resistance would add given his propensity for screwing up basic math his claim is worthless.

exactly. I think he pulled it out of his derriere.

TAM

 

[Carlos]

The resistance of the intact building itself would be thousands of times greater than air resistance.

If air resistance is able to increase total collapse times by even 20 percent, then shouldn't the addition of the resistance of the buildings themselves increase the time several thousand percent, to at least tens of minutes?"

http://www.youtube.com/watch?v=NwFHEoiUZ7o

 

[Mr. Skinny]

Sprinkler systems in the tower are thought to be damaged on the floors of the impacts based on NIST calculations. This is speculation not proven. We know the sprinklers were working on other floors from witness statements of water running down the stairs. Any assertions about what was going on on the impact floors is pure speculation. The towers survived a fire in the seventies without a sprinkler. Still we are only talking about one hour on a few floors that it needed to survive.

While I believe that the sprinkler systems on the impact floors would certainly be damaged, let's assume they weren't.

In that case, the fireball from the jet fuel would have certainly caused all of the sprinkler heads to open. They are not intended to operate like this for office environments. They are designed to have a few sprinkler heads (perhaps 4 to 6 sprinkler heads total) operating with sufficient water pressure and flow to provided the needed water density and distribution to extinguish (or at minimum halt/slow the spread of) the fire.

When all the heads open up at once, you get a low flow of water from each head with insufficient pressure to create an "umbrella" of water from the head. Basically, you're then left trying to put out a bonfire by pissing on it - it's just not gonna work.

 

[cantonear1968]

Hoffman of course provides no substantiation for his claim about how much time air resistance would add given his propensity for screwing up basic math his claim is worthless.

But why let substantiating your claims get in the way of a truthers appeal to authority? Especially when Hoffman can come up with the totally **logical** explanation of 1,000,000 ceiling tiles made of explosive nanothermite!

 

[Patriots4Truth]

http://www.youtube.com/watch?v=NwFHEoiUZ7o

one of my favorite autechre songs

 

[Patriots4Truth]

15 seconds is about 65% more then 9.2 seconds. So you are saying air resistance alone would slow down steel beams and concrete by 65%? What do you base this on?

The fact that you think that the resistance of a single floor should slow things down at all means you have NO CONCEPT of momentum.

You are the weakest link, goodbye.

TAM

I believe the momentum wouldn't have been enough for free fall until at least a second or two later in all 3 of the WTC collapses.

Adding on: I guess we need the world's top notch architects and engineers to prove this theory of mine

 

[beachnut]

... In a vacuum, a block of wood (or lead) would take 9.2 seconds to fall from the tower's roof. In the air a block of wood, say ten inches on a side, might take 50 percent longer than in a vacuum. Fifteen seconds, a good estimate for the total time of collapse of the North Tower, is about the time it would take our block to fall from the roof. The rubble from the Tower probably had similar average density to our block of wood, ....

LIE! You have no clue. The rubble from the WTC was tons of STEEL, like the elephant and the feather, you don't know physics.

The time for collapse based on momentum is just over 12 seconds - this is physics and you don't grasp physics do you make up a moronic wood analogy when the WTC towers are made of steel. FAIL

Why expose your complete ignorance using failed dolts as your source? Fire did it you can't grasp reality of fire, you post more delusions to support your failed physics, and prove it!

Your good estimate is based on your lack of knowledge of physics; this is funny, too bad you can't figure and out and think you are smart at this.

Fire is the topic, I would avoid your moronic physics analogies in the future. wow

who Stundied this?

wow, the post above is more failed physics; you have no clue. wow

if you bring up physics, you need to know physics. Wow

 

[T.A.M.]

I believe the momentum wouldn't have been enough for free fall until at least a second or two later in all 3 of the WTC collapses.

Adding on: I guess we need the world's top notch architects and engineers to prove this theory of mine

you "believe"? Well my son believes in Santa Claus...I don't put much weight in "belief", so you'll have to do better. How about some calculations, or were just pulling this statement from the same place Hoffman pulled his "air resistance" estimate?

TAM

 

[Nonpareil]

Adding on: I guess we need the world's top notch architects and engineers to prove this theory of mine

To prove what? That a building fell at free-fall speed? That doesn't take "the world's top-notch architects and engineers" to prove. It's a simple application of perfectly understandable mathematical equations. Given time, even I could work it out, and I don't have a physics degree (I do have a lot of physics experience - part of the engineering curriculum for every field is physics - but my personal engineering expertise is computers).

The math really isn't complicated. I already gave you a link to a paper wherein the equations are worked for you. Here's what it has to say on the subject:

An Assessment of the Time Delays Involved in the WTC Collapse Events

The “true” collapse time of a WTC Tower is made up of two components, the free-fall time (in a vacuum), t_f, plus time delay corrections associated with overcoming the retarding forces acting on the collapsing floors, t_d. Thus:

t_c = t_f + t_d​

The retarding forces are of three types: air resistance, and what we shall call the crushing and bending resistance of a WTC Tower. Crushing resistance refers to the forces involved in fracturing and crushing the concrete floors. Bending resistance refers to the forces involved in bending structural steel components, which could be whole columns or individual bolts and welds, to the point of failure by fracture. We will now consider these three retarding forces in detail:

(i) Air Resistance

The downward force, F_D, acting on an object in free-fall is given by:

F_D = Mg

Where M is the mass of the object in kg, and g is the acceleration due to gravity equal to 9.81 m/s².
The upward force acting on an object in free-fall is the air resistance, F_U, given by:

F_U= ½ pAC_dv²
Where p is the density of air equal to 1.225 kg/m³ at sea level; A is the effective area of the object in m²; C_d is a dimensionless quantity known as the coefficient of drag that has values in the range 0.5 to 1.0; v is the instantaneous descent velocity in m/s. (The so-called terminal velocity is attained when F_D = F_U)
Let’s apply these equations to the WTC 1 case of the upper block of 14 floors falling onto the floor below:

M = 14 x {510,000,000/110} = 6.49 x 107 kg

Hence,

F_D = 6.37 x 10⁸ Newtons

We will take A, the effective area of the falling block of floors, to be the net geometrical area of a WTC floor or 2909 m². We will assume a drag coefficient of 0.67. We consider two cases: The air resistance at the lowest impact velocity of 8.52 m/s and the air resistance at the highest impact velocity of 90.2 m/s. For the first case we find,

F_U = ½ x 1.225 x 2909 x 0.67 x 72.59 kg m/s2 = 8.67 x 104 Newtons

Clearly, for this case, air resistance is negligible compared to the downward force of gravity.
For the second case we have,

F_U = ½ x 1.225 x 2909 x 0.67 x 8136 kg m/s2= 9.71 x 106 Newtons

Thus the air resistance force is about 100 times greater than the first case because of the higher velocity; but even this value of F_U is only 1.5 % of the downward accelerating force. We conclude that air resistance is not a significant factor in the collapse of the WTC.

Here's the link again.

So you know the air resistance. You should be able to calculate whether or not the building fell at free-fall speeds. HINT: It didn't.

 

[Patriots4Truth]

All I'm saying is that the resistance from the the bottom block (tube/s - whatever you want to call it) would have been great enough for free fall to not happen until later in the collapse for all 3 buildings.

 

[T.A.M.]

All I'm saying is that the resistance from the the bottom block (tube/s - whatever you want to call it) would have been great enough for free fall to not happen until later in the collapse for all 3 buildings.

No, because the resistance was only for one floor at a time. The top section only needed to crush the one floor immediately in contact with it as it fell, then that greater mass (top section plus floor below it) moved on to the next floor, and so on....the mass got bigger, so did the momentum...right from the get go.

TAM

 

[beachnut]

All I'm saying is that the resistance from the the bottom block (tube/s - whatever you want to call it) would have been great enough for free fall to not happen until later in the collapse for all 3 buildings.

All three building very slow compared to free-fall. But you don't understand reality, you post delusions.
And again, you failed to do the physics, and you are wrong.

Sorry, you need to do the equations, you have to put in the numbers, you can't post nonsense like you do and proclaim conclusions based on nothing but lies you looked up with your google, filter to display stupid ideas on 911.

Why does the chief structural engineer agree with me that impacts and fires brought down the towers he designed structurally? Fire.

Hoffman debunks himself.

 

[Patriots4Truth]

The time of the start of the collapse to the time of freefall is the most suspect. This happened too quickly for a steel framed building.

 

[beachnut]

Sprinkler systems in the tower are thought to be damaged on the floors of the impacts based on NIST calculations. This is speculation not proven. We know the sprinklers were working on other floors from witness statements of water running down the stairs.
...

The water running down the stairs was because the water system was BROKE. You debunk yourself like all of 911 truth, failure to launch based on lack of knowledge and believing in your own BS nonsense of how things work. 9 years of failure, followed by more moronic repeated failure as if they were trying to be more failed than before.

Wow, you are debunking 911 truth faster than free-fall.

 

[T.A.M.]

WTC1/2 never reached free fall, so what are you talking about? WTC7 had part of itself, the north face, fall at free fall for only 2.25 seconds. Get the freefall argument out of your head...it is debunked...long ago.

TAM

 

[Nonpareil]

All I'm saying is that the resistance from the the bottom block (tube/s - whatever you want to call it) would have been great enough for free fall to not happen until later in the collapse for all 3 buildings.

This still doesn't require the input of the world's greatest architects and engineers. If it does, why do you believe it? They haven't said anything about it. If it doesn't, why do you believe it? It hasn't been proven.

And if it is true, what does it matter? If the buildings didn't fall at free-falls speeds for the entire time, then there was not "zero resistance", and the controlled demolition theory is shot anyway.

 

[Patriots4Truth]

This still doesn't require the input of the world's greatest architects and engineers. If it does, why do you believe it? They haven't said anything about it. If it doesn't, why do you believe it? It hasn't been proven.

And if it is true, what does it matter? If the buildings didn't fall at free-falls speeds for the entire time, then there was not "zero resistance", and the controlled demolition theory is shot anyway.

The time of the start of the collapse to the time of freefall is the most suspect. This happened too quickly for a steel framed building.

There wasn't enough axial weight coming from the top block/tube to allow free fall to happen so quickly into the collapses. The reason that free fall was achieved so quickly is explosives

 

[triforcharity]

The time of the start of the collapse to the time of freefall is the most suspect. This happened too quickly for a steel framed building.
There wasn't enough axial weight coming from the top block/tube to allow free fall to happen so quickly into the collapses. The reason that free fall was achieved so quickly is explosives

Argument from personal ignorance noted.

Show us the math. We here, love math.

Got Math????

 

[Patriots4Truth]

WTC1/2 never reached free fall, so what are you talking about? WTC7 had part of itself, the north face, fall at free fall for only 2.25 seconds. Get the freefall argument out of your head...it is debunked...long ago.

TAM

*replace everywhere I said freefall with pretty damn close to freefall if you so wish

 

[T.A.M.]

*replace everywhere I said freefall with pretty damn close to freefall if you so wish

12-13 seconds seem to be the most accurate times for the WTC1 and 2 collapses, if you do not include the core, which stood for a few seconds after the tower collapsed. 12-13 seconds is 25-30% longer then free fall. How is that "pretty damn close"?

Mom I got a 60% on my exam....that is pretty close to a 90%.

TAM

 

[T.A.M.]

The time of the start of the collapse to the time of freefall is the most suspect. This happened too quickly for a steel framed building.

There wasn't enough axial weight coming from the top block/tube to allow free fall to happen so quickly into the collapses. The reason that free fall was achieved so quickly is explosives

So now you have resorted to giving us your uneducated opinion based not on scientific laws or calculations, but based on your "intuitive" sense of how you think things should have happened.

Well there is no counter argument to that...there is no need...self debunked by virtue of incredulousness.

TAM

 

[Patriots4Truth]

12-13 seconds seem to be the most accurate times for the WTC1 and 2 collapses, if you do not include the core, which stood for a few seconds after the tower collapsed. 12-13 seconds is 25-30% longer then free fall. How is that "pretty damn close"?

Mom I got a 60% on my exam....that is pretty close to a 90%.

TAM

You have to look at the different stages. Even NIST can tell you that.

 

[T.A.M.]

Very very vague non-answer. You should just hang up the skates my friend, in this area you are over your head.

TAM

 

[Patriots4Truth]

So now you have resorted to giving us your uneducated opinion based not on scientific laws or calculations, but based on your "intuitive" sense of how you think things should have happened.

Well there is no counter argument to that...there is no need...self debunked by virtue of incredulousness.

TAM

Not self-debunked, unanswered

Now where's a distinguished independent physicist/engineer I can contact for the answer? My intuition also tells me that most of the scientists posting in the 9/11 conspiracy section of this forum here are biased.

 

[T.A.M.]

Go look up a local ASCE engineer in your phone book. If you are not from America, contact your local Engineering society, and ask them for some...or, once again, go to the yellow pages.

We await your report.

TAM

 

[Mancman]

You hardly have any plane left in PA and at the Pentagon, but now all of a sudden the plane debris is overloading the tower floors? In your so called raging inferno no less. I guess the aluminum should have survived what you claim the steel didn't. Yeah right.

Hey guys we should absorb the wisdom from this one, I never knew that when a plane is smashed into tiny pieces, it no longer weighs as much as when it was intact, fascinating.

 

[beachnut]

The time of the start of the collapse to the time of freefall that is most suspect. How quickly that happened.

No subject, no building, no idea.

WTC7 started collapsing when the penthouse fell through the WTC 7! That was longer than free fall time for WTC7. This means the interior of the WTC7 was collapsing while the facade only showed deformation. The total time of collapse for WTC 7 was over 2 times the free fall time. In your vacuum with a piece of wood, or feather. You don't understand drag very well.

WTC 1 and 2 fell very slow compared to free-fall, but then you don't do physics so you don't understand or care to research what was going on. The fact is the cores of the WTC towers remained standing well after most the building collapsed. Further, the tower itself is clearly seen still standing while debris out side of the building beats the collapse of the building.


WTC 7 took over 15 seconds to collapse; next time explain with numbers why 15 seconds is close to free-fall. You must of missed the penthouse falling into WTC 7. 911 truth fails to tell you the collapse started with the penthouse and internal failures. oops

 

[Nonpareil]

The time of the start of the collapse to the time of freefall is the most suspect. This happened too quickly for a steel framed building.

When, exactly, did the building reach free-fall speeds?

How fast is "too fast for a steel-framed building"?

What mathematical evidence do you have to back up your answers to the above two questions?

*replace everywhere I said freefall with pretty damn close to freefall if you so wish

How close is "pretty damn close", and how close is too close to be impossible in a collapse?

What mathematical evidence do you have to back up your answer to the above question?

Not self-debunked, unanswered

Now where's a distinguished independent physicist/engineer I can contact for the answer? My intuition also tells me that most of the scientists posting in the 9/11 conspiracy section of this forum here are biased.

You've got the equations. I gave them to you, so I know you've got them. You can work it yourself.

Or, failing that, you could go to a university of some kind, preferably one with an emphasis on engineering, such as Rose-Hulman, and ask the professors.

Or you could contact ASCE.

 

[Patriots4Truth]

I'm not interested in the speed of the whole collapse for my math problem that I will have to impose upon some unbiased physicists/engineers - just the acceleration until freefall (or near freefall speed) and the changes in acceleration as each floor collides. As for wtc7 I would be most interested in the time right after the penthouse collapse until free fall (or near free fall speed) for both the north tower and the rest of the building separately.

 

[Patriots4Truth]

I'm pretty sure you are missing lots of equations Pure_Argent. You didn't even get into the axial stuff.

 

[Patriots4Truth]

I just discovered that some of the "Jolt" talk has some things to do with what I'm interested in. Now I have a lot of researching to do to find out more about Jolt talk

 

[Nonpareil]

I'm not interested in the speed of the whole collapse for my math problem

Why not? We're talking about the whole collapse, after all.

just the acceleration until freefall (or near freefall speed)

Again, how close is "near free-fall speed"? How close to free-fall speed is impossible for a collapse?

I'm pretty sure you are missing lots of equations Pure_Argent. You didn't even get into the axial stuff.

Me, personally? No. But that's not what I'm talking about, and if you had actually read what I posted, you would know that. I gave you a link - multiple times - to a paper which contains all the relevant math in one simple, easy-to-read format. Have you read it?

 

[fess]

*replace everywhere I said freefall with pretty damn close to freefall if you so wish

Would you make up your damn mind?

 

[Patriots4Truth]

P4T:I'm not interested in the speed of the whole collapse for my math problem

Why not? We're talking about the whole collapse, after all.


P4T:just the acceleration until freefall (or near freefall speed)

Again, how close is "near free-fall speed"? How close to free-fall speed is impossible for a collapse?


P4T:I'm pretty sure you are missing lots of equations Pure_Argent. You didn't even get into the axial stuff.

Me, personally? No. But that's not what I'm talking about, and if you had actually read what I posted, you would know that. I gave you a link - multiple times - to a paper which contains all the relevant math in one simple, easy-to-read format. Have you read it?

I'm sorry if I somehow misled you. I'm only interested in the speed/acceleration of the collapse up to when the collapses reached that steady drop rate around freefall speed.

-------------------------

It turns out that "Jolt Talk" has some convincing arguments along with the time period I'm interested in. If there is no jolt/s at the start of the collapse then surely there wasn't the gravitational/fire collapse as told in the original story.

Jolt Talk youtube part 1
Jolt Talk youtube part 2

It appears that there was no jolt/s. I smell explosives

 

[Carlos]

One of the truthers biggest mistakes is to consider the building as if it were a solid block.

Buildings are made up of floors and columns.

When the columns of one floor are still intact they offer great resistance.

When the columns of the same floor fail by buckling they offer poor resistance.

And the process repeats. Something like this:

Floor: N
Status: still intact
Space/displacement (ΔS): some inches
Acceleration: poor

Floor: N
Status: failed by buckling
Space/displacement (ΔS): 12 ft
Acceleration: great
______________

Floor: N-1
Status: still intact
Space/displacement (ΔS): some inches
Acceleration: poor

Floor: N-1
Status: failed by buckling
Space/displacement (ΔS): 12 ft
Acceleration: great
______________

Floor: N-2
Status: still intact
Space/displacement (ΔS): some inches
Acceleration: poor

Floor: N-2
Status: failed by buckling
Space/displacement (ΔS): 12 ft
Acceleration: great
______________

Floor: N-3
Status: still intact
Space/displacement (ΔS): some inches
Acceleration: poor

Floor: N-3
Status: failed by buckling
Space (Δs): 12 ft
Acceleration: great
______________


So, under these conditions, the average acceleration during the collapse would be closer to the "great" or "poor"?

 

[Sivan Kurzberg]

Hey guys we should absorb the wisdom from this one, I never knew that when a plane is smashed into tiny pieces, it no longer weighs as much as when it was intact, fascinating.

Hmmm, so I guess if you were to burn a campfire all night in morning the remaining ash would weigh the same as all the wood you threw on the fire huh? fascinating

I was referring to how it's claimed that much of the plane was incinerated in the fire at the Pentagon for example. It's also claimed that the molten metal witnessed at the towers was aluminum. One can only assume if the fire was hot enough to compromise the steel to the point of collapse, then most if not all of the floor contents should have burned up in smoke. Drywall, carpet, furniture, etc. Also if the aluminum from the plane turned molten it would run down the elevator shafts, broken floors, windows, and down the stairs making the loads not so concentrated to one area. Not to mention that much of the plane should have been shredded initially breaking through the outer cage which would have also distributed the load throughout several floors.

 

[little grey rabbit]

School of Architecture ......masons.....damn those masons...

 

[Sivan Kurzberg]

The water running down the stairs was because the water system was BROKE. You debunk yourself like all of 911 truth, failure to launch based on lack of knowledge and believing in your own BS nonsense of how things work. 9 years of failure, followed by more moronic repeated failure as if they were trying to be more failed than before.

Wow, you are debunking 911 truth faster than free-fall.

You don't know that. It might have just been water from WORKING sprinklers running down the stairs.