structural engineer leslie robertson interview

Originally posted by ANOK

Originally posted by wmd_2008
Re planes flying through the steelwork you see example of things like this all the time Martial Artists hands through,timber ,bricks even ice,the pumpkin gun soft object hits a harder object but due to the energy involved it causes damage.
Its funny but the planes get called flying beer cans when thay hit the towers but when one hit the Pentagon a building DESIGNED to resist attack people complain that little is left of the plane!

yeah lol what idiots...

You see bro you have to understand physics and how to apply it to different situations. A guy chopping wood with his hand is not the same as aluminum hitting steel.

The bones in your hand have more mass than wood, bricks, or ice. It is hard to do but sry it doesn't fit planes hitting buildings.

As far as the pentagoon goes... Newton says that when objects collide the force on each object is equal, except the deceleration, or bounce back which is relative to it's mass. So, when an object hits another object the object with the least mass receives the most damage.

I'm sure you've seen the F-4 hitting the concrete vid? That is a perfect example, plane is destroyed concrete is not, more mass in the concrete. If the plane had the more mass it would have gone through the concrete. So, seeing as they plane went through that reinforced wall at the pentagon, it could not have also been destroyed by going through that wall. Also there was nothing else past that wall that would have destroyed the plane. That leaves just the fire. Where is the plane?

How do your BONES have more mass than say a 2" concrete slad or 6" thick block of ice please explain!

IF YOU THINK PLANES are made like aluminium cans LETS make a plane like that and let YOU fly in it.

IF YOU CAN ACTUALLY GRASP this think of the forces applied to a planes wing at and just after take of when the plane banks/turns with a FULL LOAD of fuel, planes are not as FRAGILE as you think SO get a grip YOU SAW THEM fly through the walls!
You need to BRUSH up on your physics MATE!

Your wrong about the F4 video when that test was done I believe it was to show the strength of walls in a Nuclear Power Station when concrete is made for normal construction cement,water,sand and stone chips(aggregate) nuclear power stations concrete mix cement,water, sand (cyliner heads,ball bearings any chunk of steel that can be found) the reason being strength and to help with shielding!!!

Originally posted by CameronFox
Please define "destroyed."

The pictures I posted speak for themselves. Please point out any jet fuel fires in any of those lobby or basement videos. Please also point out any charring or burning that would be caused by those fires. Any black/burnt objects? Soot? There is none and you won't find any.

Originally posted by CameronFox
As I am sure your research has show you, the NIST report states that less than 15% of the fuel burned in the spray inside the building. Pretty close to the same amount was with the fireball outside the building. That leaves well over 1/2 the fuel still inside the building.

A short paper that deals with the jet fuel with references to NIST:

www.journalof911studies.com...

Even NIST admits in its Final Report, "The initial jet fuel fires
themselves lasted at most a few minutes."

Had your link worked, the above quote would have been on page 182. Do you think the kerosene said "hmm, we'll burn half our selves up in a fireball, the rest of us will cruise around for a little bit, check out this tower before we burn it down. maybe head downstairs...".

If you take a 5 gallon gas can and fill it up with any type of fuel, then dump it on the ground and ignite it, do you think half of it is going to burn? Every drop will ignite in seconds. All of the jet fuel from the planes either burned up in the fireball or was burning in any office furnishings that might have soaked it in. Either way, all of it was burning in seconds.

Finally, debunkers haven't got a single source to prove the jet fuel somehow magically transformed itself into several powerful explosives over a certain amount of time and destroyed the lobby and the parking garage. There was massive damage to the parking garage in the pictures I've shown.

Debunkers are just speculating or making things up to explain away the obvious. People were killed and severely burnt in the elevators. Where would the explosives be placed if they were to weaken the lower levels of the WTC? In the cores. What are also in the cores? The elevators. Thank you for reading.



[edit on 21-3-2009 by _BoneZ_]

Originally posted by wmd_2008
How do your BONES have more mass than say a 2" concrete slad or 6" thick block of ice please explain!

I'm not positive but I believe that it has to do with density (mass/volume).

At any rate, airplane skeletons are made of aluminum alloys that are denser and stronger than steel I believe.

So, IMO, there were planes, and they did enter the building by way of bolts and welds failing and possibly some steel shearing.

Your wrong about the F4 video when that test was done I believe it was to show the strength of walls in a Nuclear Power Station when concrete is made for normal construction cement,water,sand and stone chips(aggregate) nuclear power stations concrete mix cement,water, sand (cyliner heads,ball bearings any chunk of steel that can be found) the reason being strength and to help with shielding!!!

Isn't depleted uranium used also as it's 1,000 times better than lead at shielding (absorbing) radiation?

Also, I was asking you how the upper cap just dropped when steel columns would deform and buckle to one side (rigid structures buckle in the same direction....path of least resistance) not straight down.

[edit on 3/21/2009 by Griff]

Originally posted by Griff

Originally posted by wmd_2008
How do your BONES have more mass than say a 2" concrete slad or 6" thick block of ice please explain!

I'm not positive but I believe that it has to do with density (mass/volume).

At any rate, airplane skeletons are made of aluminum alloys that are denser and stronger than steel I believe.

So, IMO, there were planes, and they did enter the building by way of bolts and welds failing and possibly some steel shearing.

Your wrong about the F4 video when that test was done I believe it was to show the strength of walls in a Nuclear Power Station when concrete is made for normal construction cement,water,sand and stone chips(aggregate) nuclear power stations concrete mix cement,water, sand (cyliner heads,ball bearings any chunk of steel that can be found) the reason being strength and to help with shielding!!!

Isn't depleted uranium used also as it's 1,000 times better than lead at shielding (absorbing) radiation?

Also, I was asking you how the upper cap just dropped when steel columns would deform and buckle to one side (rigid structures buckle in the same direction....path of least resistance) not straight down.

[edit on 3/21/2009 by Griff]

Lead is more often used sometimes with a small coating of depleated uranium,

Lead is a better absorbtion material due to its structure it is also easier to work with.

The depleated uranium is stronger and helps the lead maintain shape and rigidity.

Originally posted by Achorwrath
Lead is a better absorbtion material due to its structure it is also easier to work with.

DU is twice as dense as lead and is used for radiation shielding.

8. Uses of Depleted Uranium

* Storage of Radioactive material costs money, so uses are being found for DU.
* As Uranium is 1.7 times as dense as lead, it is being used as a replacement for lead and other heavy metals.

* Starmet (Formerly Nuclear Metals Inc) makes products from DU, including Radiation Shields, Aircraft Ballast and Weapons.
* Alliant Techsystems Inc and other companies also make weapons from DU.
* Submissions to a recent US government report suggested other uses for DU such as flywheels.

www.geocities.com...

I'm not going to argue about it's use in nuclear power plants as a shield because I don't know if that is true' The only reason I bring it up is because of the F-4 test against concrete....if that concrete had dense DU embedded into it, then we can understand why the F-4 disintegrated. But I do know that DU is denser and shields more radiation than lead.


[edit on 3/21/2009 by Griff]

I think that wall was not meant for a reactor but is consistanly listed as being designed to withstand a nuclear blast.

Which would indicate it was significantly more sturdy than the steel of the WTC.

As they did not test their design Vs a nuclear blast.

reply to post by _BoneZ_


The fuel which penetrated the elevator shafts dispersed as an aerosol as
it fell down the shaft - the fuel aerosol mixed with air and formed an
explosive mix. Same principal as automobile engine - mix of fuel vapors
and air when ignited explodes Perhaps you should consult the NFPA
(National Fire Protection Association) manual - the section on explosions
which goes into detail on fuel mist/vapor explosions

Doesnt take a lot of fuel dispersed as aersol to cause an explosion - not
all the fuel was burned off in this manner.

What fuel not consumed in the initial fireballs acted an accelerant and ignited the combustibles in the building. Moden high raise buildings are
filled with combustible materials, synthetics and plastics combined with
tons of paper. The jet fuel set fire to all these materials - same as
squirting lighter fluid (aka kerosene) on charcoal. The lighter fluid
burns off in few minutes, but the charcoal continues to burn.

Estimate by Vincent Dunn, retired deputy chief FDNY and authir of
"COLLAPSE OF BURNING BUILDINGS" estimates sufficent fuel in each floor
of high raise to burn for 2 hours.

Originally posted by wmd_2008
How do your BONES have more mass than say a 2" concrete slad or 6" thick block of ice please explain!

Do you know what mass is? It has nothing to do with size or weight, mass is determined by the amount and type of atoms a material contains and the energy used to bind them together.

IF YOU THINK PLANES are made like aluminium cans LETS make a plane like that and let YOU fly in it.

Regardless aluminium has less mass than steel. Aircraft aluminium included. If they were to make it stronger than steel it would be too heavy for aircraft use. If they could use steel they would but it's too heavy.

IF YOU CAN ACTUALLY GRASP this think of the forces applied to a planes wing at and just after take of when the plane banks/turns with a FULL LOAD of fuel, planes are not as FRAGILE as you think SO get a grip YOU SAW THEM fly through the walls!

I never said they were fragile. It's just simple physics, when two objects collide the forces are equal on both objects. Steel has more mass than aluminium. The only parts that could have effected the columns were the engines and other smaller parts, not objects that would slice through steel. Simply denting, or breaking of small sections of columns would not cause a global collapse.

I was a jet engine mech in the Navy, I know aircraft.

Your wrong about the F4 video when that test was done I believe it was to show the strength of walls in a Nuclear Power Station when concrete is made for normal construction cement,water,sand and stone chips(aggregate) nuclear power stations concrete mix cement,water, sand (cyliner heads,ball bearings any chunk of steel that can be found) the reason being strength and to help with shielding!!

Huh how am I wrong, your explanation has nothing to do with what I said? Mass determines how strong something is, so as I said the concrete had more mass than the plane, basic physics. BTW it's 'you're wrong'.

You need to BRUSH up on your physics MATE!

What is mass now?

[edit on 3/21/2009 by ANOK]

reply to post by thedman


If you had read my post, you would've seen that there were at least 3 sub-level explosions in the time frame it took the survivors to get out of the lower levels of the building. Most of the witnesses said there was at least one of these explosions, seconds BEFORE the plane impacted.

And sorry, but once fuel is ignited, it's not going to leave some behind to explore other places before it magically ignites. Either the fireball (already ignited fuel) travelled down the elevator shafts (which is impossible because fire and heat travels up) or the liquid jet fuel travelled down the shafts and some invisible fires ignited the liquid fuel.

Lastly, your logic suggests that the fuel would've picked floors to stop on. That's also not possible.

Also, you can't produce any factual papers that would suggest your theory is correct, so please stop peddling your theories as fact. You should put "in my opinion" or "I believe" or something along those lines.

What we do know as fact is that in controlled demolitions, they weaken the structure in the very lower levels, which you can see in the pictures, videos and witness testimony of the very extensive damage to the parking garage up to the lobby. We also know that in most controlled demolitions, there are jets of dust/smoke that are caused by high powered explosives being detonated and we also see that at the WTC towers as they both collapse. We also see both towers fall at near free-fall speeds like in every controlled demolition because the resistance was taken away allowing the towers to free-fall unimpeded.

Most every single aspect of controlled demolition is observed at the WTC and NONE of the aspects of fire-induced collapse is observed:

www.ae911truth.org...


On a side note, if you haven't seen "9/11 Eyewitness" (it's on Google video), you can hear these explosions and see new smoke rising from the bases of the towers. These are the explosives being detonated in the basement levels to weaken the under-infrastructure of the buildings to bring them down.

Originally posted by thedman

 

The fuel which penetrated the elevator shafts dispersed as an aerosol as
it fell down the shaft - the fuel aerosol mixed with air and formed an
explosive mix. Same principal as automobile engine - mix of fuel vapors
and air when ignited explodes

You keep saying this as if it's fact.

How did the fuel disperse as an aerosol?

No it's not the same as a car engine. It would have to be a diesel engine (jet fuel is diesel), so as well as atomising, through special jets, the fuel also has to be compressed, thus jet engines have compressor sections to compress the air before the fuel is added, car engines a piston.

How did the fuel get atomized in open air?. And even if the fuel did ignite it would not explode unless under pressure (compressed), how did the oxygen and fuel get compressed? This is a silly and impossible hypothesis.

I challenge you the dman, to go get some diesel fuel, or even jet fuel if you can, and see if you can get it to ignite and explode in open air.
To be a theory it has to be testable and that test repeatable. Until you can do that I'd drop this silly argument.

[edit on 3/21/2009 by ANOK]

Originally posted by _BoneZ_

The pictures I posted speak for themselves. Please point out any jet fuel fires in any of those lobby or basement videos.

Please list combustibles in the lobby.

Originally posted by _BoneZ_

www.journalof911studies.com...

Was this paper published in a respectable journal?

Even NIST admits in its Final Report, "The initial jet fuel fires
themselves lasted at most a few minutes."

Your point?

Originally posted by _BoneZ_Had your link worked, the above quote would have been on page 182. Do you think the kerosene said "hmm, we'll burn half our selves up in a fireball, the rest of us will cruise around for a little bit, check out this tower before we burn it down. maybe head downstairs...".

This was explained to you above.

Originally posted by _BoneZ_
Debunkers are just speculating or making things up to explain away the obvious. People were killed and severely burnt in the elevators. Where would the explosives be placed if they were to weaken the lower levels of the WTC? In the cores. What are also in the cores? The elevators. Thank you for reading.

Bonez, you went into detail about explosions and not being "hollywood"... good point... now tell me, if you are close enough to an explosion made by TNT, C4, cutter charges... to be burnt...what would be left of your body?


So, the bombs were planted in the basement? They went off an HOUR before the collapse? This served what purpose?

Jet Fuel Information

Here is a pretty good exchange between SwingDangler and Ryan Mackey:

Posted by Swing Dangler

First, before I accept this information, can you source the 24,000 pounds of fuel from the NIST report.
Second, what class of explosives are you referring to?
Third, can you provide the necessary numbers to prove jet fuel caused the amount of damage in the basement levels?

Fourth, why are you using the energy equivalent of remaining jet fuel after the impact to prove 100,000 pounds of explosives in each basement had to be used? You would be better off to show the process and data behind the jet fuel to prove it caused the destruction witnessed.

If you sincerely believe in the jet fuel excuse then it should be easy to answer the following questions:
1. Can you source the amount in pounds of jet fuel in each tower after the initial impact and explosion?

2. Second, can your provide the fuel/air ratio necessary for the explosion as well as blast pressure data?

3. Third, can you provide the calculations supporting the official story that jet fuel fireball caused the damage in the basement? You know those energy
numbers NIST didn't provide in their report.

4. Fourth, can you provide any witnesses who saw the amount of jet fuel you claimed did or could do the damage in the multiple levels of the basement?

Yet debunkers accept as fact the jet fuel excuse without anyway to quantify the damage to the basement with numbers that mean anything despite the historical record of terrorists, the FBI's working theory, the eyewitness descriptions, etc, etc.! Go figure!

In order, here are the answers.

1. 24,000 pounds of fuel is the estimate that NIST gave for the amount of fuel running into the lower structure. NIST estimated that there were 66,100 pounds of fuel in AA11 and 62,000 pounds in UA175 at impact (NCSTAR1-2B, pg. 171). Of those totals, NIST estimated that 20% was consumed in the initial fireballs, 40% was distributed on the impact floors, and 40% drained or flowed into the lower structure (NCSTAR1-5F pg. 56).

Yes, these are rough estimates, and I am on record criticizing these estimates in my whitepaper. However, working out a better estimate either through investigation or modeling would be a nontrivial undertaking, and for now, it's the best we have. Certainly it's in the right ballpark.

2. I'm referring to all chemical explosives. The energy density of Jet A is approximately 43 MJ / kg (remember that number for later). The typical yardstick, TNT, is a mere 4.2 MJ / kg, ten times less. Exotic, impractical, high-powered explosives such as octanitrocubane only get up to about 7.5 to 8 MJ / kg, still a factor of five below Jet A. It really doesn't matter what explosive compound you fantasize about, they just aren't going to give you more energy than the jet fuel, unless you propose a fantastic amount of it. I can only assume you don't know much about explosives.

3. As a matter of fact, I can prove that jet fuel could cause the damage seen. This step is a long one.

To begin, let us model the problem as follows: Suppose the entire basement of a Tower suffered an overpressure event, sufficient to cause the observed damage. We can describe the damage qualitatively:

* There was extensive damage to interior and furniture over a wide area.
* Damage to the structure, however, was minor to negligible.
* There are no reports of anyone being killed by the blast. The principal danger was fire.

Based on these factors, we estimate that the magnitude of the pressure pulse was moderate, in the range of 1 PSI, since overpressures of 5 PSI typically damage or destroy all but hardened structures, and would have surely killed many who were inside. Nevertheless, we want to overestimate the energy requirement to make absolutely certain that my contention -- that the jet fuel is more than sufficient -- is true. We will use the higher, less credible estimate of 5 PSI. In proper units, this is 34.5 kPa.

Next, suppose the deflagration pressurized the entire volume of the basement to 5 PSI. This is another deliberate overestimate. In actual fact, the overpressure would be a wave rather than a static phenomenon, and thus the true energy requirements are much, much lower. Let us suppose that the basement area was the size of the WTC footprint (64 m square) times a depth of 25 m, sufficient for at least six sublevels. This is a total volume of roughly 100,000 m3.

Next, we work out the energy required to raise that entire volume by the pressure differential required. There are several ways to calculate this, depending on your model of the process. The simplest is to consider the Bernoulli energy density, in which case E = ΔP V, but this only applies in non-dissipative processes along streamlines, and is generally an underestimate. At the other extreme, we can consider an increase in pressure due to heating in a constant-volume process, which is maximally entropic and will overestimate the energy required. We will use the latter extreme.

To solve the energy density in this fashion, we simply apply the Ideal Gas Law, in this case expressed as follows:

ΔP V = n R ΔT (1)

where n is the number of moles of gas and R is the gas constant.

After we solve for the increase in temperature, we can then extract the energy required from the simple expression:

E = ρ V cs ΔT (2)

where ρ is the density of air and hence ρ V is the total mass of air, and cs is the specific heat capacity of air.

Substituting for ΔT in (2) using a rearrangement of (1), we find that:

E = ρ V2 cs ΔP / n R (3)

Or, using the shorthand N = ρ V / n where N is the molar mass of air, i.e. the number of grams per mol, we arrive at the answer:

E = N V cs ΔP / R (4)

Values for these constants are as follows:

* N = 28.97 g / mol
* cs = 1.012 J / g K
* R = 8.31 Pa m3 / mol K

And so we find that:

E = 3.53 V ΔP (5)

In other words, this formulation is roughly 3.5 times the energy of the Bernoulli approach. All that work for a lousy factor of 3.5. So it goes.

We are now ready to compute the answer. In our problem, V = 100,000 m3, and ΔP = 34.5 kPa. Therefore, the energy required in our model -- understanding, again, that it is a deliberate overestimate -- is equal to:

E = 3.53 (100,000 m3) (34.5 kPa) = 12.5 GJ

12.5 GJ is a lot of energy. But how much is that in terms of jet fuel? Now recall that jet fuel has an energy density of 43 MJ / kg. This means, in order to get this much energy, we need (12.5 GJ) / (43 MJ / kg) = 290 kilograms of jet fuel.

That's all. 290 kg, or about 640 pounds, 375 liters, just under 100 US gallons.

I remind you, this is a wild overestimate. In practice, the fuel will probably not all burn at once, and will not be terribly efficient, but the constant-volume method above captures all of these effects. The actual number might be two to ten times smaller if we did it carefully, but that doesn't matter.

What matters is that 290 kg of jet fuel is a totally acceptable amount of jet fuel to pour down the elevator shafts. The damage seen in the basement is, therefore, perfectly reasonable.

I'll hurry through the rest of the questions.

4. To do the same amount of damage with explosives, using the ratios already discussed above, you would need about 2900 kg of TNT, or 1450 kg of the obscure and never-used octanitrocubane. Any explosive you pick will land somewhere in the middle or perhaps heavier than these figures. That's a heck of a big boom.

5. This is a repeat of Question 1. See above for the source of the jet fuel amounts.

6. I can only assume that your question about mixing ratios is a desperate clutch at straws. Jet fuel's mixture ratio is 0.044 by mass. Our 290 kg of jet fuel would thus require 6591 kg of air, or a volume of 5492 m3, or about 5% of the volume treated in the above exercise. There is plenty of air to get it done. Nice try.

7. Repeat of Question 3.

8. I have no need to provide witnesses. The level of destruction that would be wrought by my model explosion above is greater than even the most speculative cherry-picked assessment of witness reports. This is the value of doing a bracketing or "worst case" analysis. I can afford to sacrifice precision, since the effect is so obviously within the capability of a jet fuel explosion.

9. It should now be perfectly obvious why we accept the jet fuel argument, and why we reject the "truck bomb" argument. But for your benefit, I'll state it anyway:

* Remember how big the "truck bomb" was in 1993? 1300 pounds of various low to moderate explosives, call it 1000 pounds TNT equivalent. My jet fuel situation above is about five times more powerful. You'd have to spec an awfully big truck.
* Despite being smaller than my jet fuel case, the 1993 truck bomb woke up the whole damn town. No way to conceal that. Forget it. It would be totally obvious that high explosives had been used. The jet fuel, on the other hand, delivers its blast as a deflagration, and is totally consistent with witness statements, both inside and outside the structure.
* Even a smaller truck bomb, on par with the 1993 event, would have killed people through blast and shrapnel. Didn't happen. So you must have a smaller truck bomb. This contradicts the points above, thus the hypothesis is DOA.
* Unlike truck bombs, it's clear to everyone that there was jet fuel in massive quantities running all over the place. There's no evidence for explosives. The "excuse" is yours.
* How anyone would trigger a bomb coincident with a jetliner impact is almost too incredible to contemplate. Was someone watching with his finger on the button? Why? What's the point?

source

reply to post by ANOK


So tiatanium is now weaker than steel?

Link

Note Three times stronger with only 42% of the wieght.

Your argument does not hold up

Originally posted by ANOK

Originally posted by wmd_2008
How do your BONES have more mass than say a 2" concrete slad or 6" thick block of ice please explain!

Do you know what mass is? It has nothing to do with size or weight, mass is determined by the amount and type of atoms a material contains and the energy used to bind them together.

IF YOU THINK PLANES are made like aluminium cans LETS make a plane like that and let YOU fly in it.

Regardless aluminium has less mass than steel. Aircraft aluminium included. If they were to make it stronger than steel it would be too heavy for aircraft use. If they could use steel they would but it's too heavy.

IF YOU CAN ACTUALLY GRASP this think of the forces applied to a planes wing at and just after take of when the plane banks/turns with a FULL LOAD of fuel, planes are not as FRAGILE as you think SO get a grip YOU SAW THEM fly through the walls!

I never said they were fragile. It's just simple physics, when two objects collide the forces are equal on both objects. Steel has more mass than aluminium. The only parts that could have effected the columns were the engines and other smaller parts, not objects that would slice through steel. Simply denting, or breaking of small sections of columns would not cause a global collapse.

I was a jet engine mech in the Navy, I know aircraft.

Your wrong about the F4 video when that test was done I believe it was to show the strength of walls in a Nuclear Power Station when concrete is made for normal construction cement,water,sand and stone chips(aggregate) nuclear power stations concrete mix cement,water, sand (cyliner heads,ball bearings any chunk of steel that can be found) the reason being strength and to help with shielding!!

Huh how am I wrong, your explanation has nothing to do with what I said? Mass determines how strong something is, so as I said the concrete had more mass than the plane, basic physics. BTW it's 'you're wrong'.

You need to BRUSH up on your physics MATE!

What is mass now?

[edit on 3/21/2009 by ANOK]

Mass :the property of a body that causes it to have weight in a gravitational field .

Density is defined as its mass per unit volume.


The ability for someone to put their hand through a harder material has NOTHING to do with the mass of your bones.
Its all about acceleration, speed at contact and area of contact

Something for you to read then imagine its a PLANE !

cabscience.com...

Mass is not what determines STRENGTH concrtete can take high compressive loads but LOWER tensile loads NOTHING to do with mass as that WONT HAVE CHANGED.

Have A LOOK at a Castellated Steel Beam ( GOOGLE IT) resists bending better but lower Shear strength NO CHANGE IN MASS

Think about it!

Originally posted by CameronFox
So, the bombs were planted in the basement? They went off an HOUR before the collapse? This served what purpose?

Come on Cameron, you appear to be a smart guy. If you are the planner of 9/11 and had the towers laden with explosives, you're going to detonate them in a way that will be the least suspicious.

Detonating an explosive here and there while the buildings were burning or timing some of them with the plane impacts is less obvious than setting off all the explosives in the lower levels at once or in succession.

Circular argument Bonez.

Sorry but by the same theory they would be smart enough to escape all detection.

Especially since they loaded up the explosives without notice.

reply to post by Achorwrath


What are you talking about? You still think mass means weight?

Titanium 47.867 amu
Aluminium 26.981539 amu
Steel 55.845 amu (variable)

Titanium is not stronger than steel, but weight for weight it is. A good example is bike frames, a steel frame would be much heavier and stiffer, but about the same strength as a titanium frame of the same size.

Originally posted by ANOK
Do you know what mass is? It has nothing to do with size or weight, mass is determined by the amount and type of atoms a material contains and the energy used to bind them together.

What you're actually alluding to is density or relative mass per unit of volume which has a lot to do with size and weight (although mass is independant of weight which is a factor of gravity) and it could be expressed in terms of protons and neutrons per unit of volume. The hardness of a material is associated with molecular bonding and crystalline structures within the material and is fairly independant of actual mass.

It's just simple physics, when two objects collide the forces are equal on both objects.

You've simplified it a bit too much there. Think about the definition of kinetic energy and what the major component of it is (hint V^2), mass being the lesser part of it and virtually insignificant in the case of high velocities. The density of the projectile becomes a factor in the surface area of impact and therefore determines the pressure exerted on the stationary object which can only survive if that pressure is less than the UTS of the contacted area. If UTS of the area of contact is exceeded the projectile penetrates regardless of the materials involved, in this case aluminium delivering a large enough kinetic punch to a small enough surface area of steel to cause failure. Whether the failures were at bolted &/or welded connections or column sections themselves doesn't matter, the walls were broken.

Simply put, the stationary material has to be able to supply enough force to resist the projectile without breaking itself in the process. The more massive overall the stationary object is, the more inertia it has which actually enhances the possibility of local failure as less of the projectile's kinetic energy is dissipated by a transfer of motion to the overall structure.

As per usual, it's never quite as simple as we'd like it to be.

[edit on 21/3/2009 by Pilgrum]

reply to post by wmd_2008

In physical science, mass refers to the degree of acceleration a body acquires when subject to a force: bodies with greater mass are accelerated less by the same force. One says the body of greater mass has greater inertia. The mass of an amount of matter in a chemical substance is determined in part by the number and type of atoms or molecules it contains, and in part by the energy involved in binding it together (which contributes a negative "missing mass," or mass deficit). According to special relativity, energy also has mass according to the principle of mass–energy equivalence as exemplified in the process of nuclear fusion and the bending of light.[1]

en.wikipedia.org...(physics)

Originally posted by Achorwrath
Sorry but by the same theory they would be smart enough to escape all detection.

I don't think there's any means of bringing those buildings down that would escape all detection. But I don't know everything either. They did it conspicuously enough to make most people believe the official story. But not enough to make people in the know believe the official story.