Messages

@Snarky:  Yes, of course, the dynamics and affects of the impact are not addressed.  But in this thread Monkey says "Inelastic collisions are probably a more realistic model. Judy Wood explains this type of collision with the equation demonstrating that when two bodies of equal mass impact and “stick” together they will continue to travel at half their original speed, i.e. conservation of momentum.".  I wanted to point out that the assumption that the colliding bodies are of equal mass is invalid and that any conclusions based on this assumption are equally invalid. 

[RickJ]

RickJ

1. The buildings fell too quickly

Obviously a progressively increasing number of floors have more mass than an single floor.  So as the collapse proceeds, the falling mass's velocity loss is proportionally smaller and smaller.

This is incorrect. Conservation of momentum says that as two masses impact and combine (inelastic collision), then the resulting velocity decreases. This means the collapse could not have been faster than free fall speed. My argument is that resistance in the progression (assuming there's enough energy to keep it going) should slow things down and produce an overall collapse time somewhere between 10 and 100 seconds depending on how much energy is lost along the way.

Lesson on Conservation of Momentum
Mt - mass of the top 10-20 floors above the point of the plane's impact.
Mf - mass of one floor
Pn - Momentum at each floor impact (i.e. P1 is the first impact)

Assuming all floors have the approximately the same mass we can see that ...
Mt = 10*Mf or Mt = 20*Mf.

If the distance between floors is 4m between floors then at the
first impact we have

V1 = 8.85 m/s                   
P1 = V1*Mt = V1 * (Mf * 10)

If momentum is conserved then the momentum after the collision must be the same.

Pafter = Va * Ma = P1
Ma = Mt+Mf = (Mf*10) + Mf = Mf*11
Va = P1/Ma = V1 * (Mf*10)/(Mf*11) = V1*(10/11) = 8.85*10/11 = 8.045 m/s

The top plus the new floor then continue accelerating under gravity from
an initial velocity of 8.045 m/s. The velocity at the next impact (abou 12 m/s) is reduced
by a factor of 11/12th. The combined masses again continue to accelerate under gravity
starting at this new initial velocity.

As can easily be seen as the collapse progresses the reduction in velocity due to conservation
of momentum becomes less and less of a factor.  In fact it's not much of a factor to begin with
due to the mass of the upper floors.  Conservation of momentum can't used to justify a 100s
(10x free fall time) collapse time as it's effect much smaller and could even be characterized
as negligible.

[1. The buildings fell too quickly]

1. The buildings fell too quickly

Inelastic collisions are probably a more realistic model. Judy Wood explains this type of collision with the equation demonstrating that when two bodies of equal mass impact and “stick” together they will continue to travel at half their original speed, i.e. conservation of momentum. That link you provided (HERE) includes the correct governing equations to model the collapse, which when plotted look like this.

This assumes both objects are of equal masses and ignores gravatitional acceleration.  Obviously a progressively increassing number of floors have more mass than an single floor.  So as the collapse proceeds, the falling mass's velocity loss is proportionally smaller and smaller.  The velocity of the upper mass accelerates between floor collisions at 32 ft/s/s.

Judy Wood does not claim that the collapse should have taken 100 seconds. Rather, she argues that the progressive collapse or “pancake” model is fundamentally wrong.

Now I'm confussed because before, in this post you said "SOME of [Judy Wood's] the evidence is: ... 1. The towers fell at free fall speed.".

Here is a demolition expert with first hand knowledge of 911/WTC collapse who disagrees.  He explains the difference between a controlled demolition and the progressive collapse of the towers.  In doing so he clearly points out where and when the failure of the structual elements occur. 
http://www.jod911.com/WTC%20COLLAPSE%20STUDY%20BBlanchard%208-8-06.pdf

2. A larger debris pile should have resulted (not predominantly dust size)
Just from this photo it can be clearly seen that dust and debris are distributed over a much larger area than you are assuming.  Also, the article I linked above explains how the outer structual elements are thrown away from the buildings as they collapsed.


3. A larger seismic signal should have been recorded
Again in the linked article, The author and his colleagues at Protec, an authority on explosive demolition of structures, disagree (see assertion #4). 
They say that the seismic data is consistent with a building collapse and that a stronger signal would have been expected if explosives were used.  The signal was weaker because no explosives were used.

ManiacMatt

Amazing what a single vowel can do for someone...

[BitPriest]

I'm not arguing that a plane can't penetrate a building

Well, until now you have been insiting just that ... that it is physically impossible for a plane to penetrate a building.  As I understand it, this whole energy weapon idea rests upon this assumption.

Also there doesn't appear to be calcyulations of this sort on Judy Wood's site.  Perhaps you could be more specific and direct me to what you ar referring.

[edit]added link physically impossible to post containing this:

...
BitPriest
...
I don't doubt the towers were hit by what appeared to be planes. My argument is that many have missed the subtlety of the impact. When looked at critically one should realise that what we saw was physically impossible. Some people may argue that a bullet can penetrate a given material and therefore a plane can penetrating a building. However bullets are designed to do that - they are designed as a weapon. Passenger airliners are not designed as a weapon. Planes have fragile wings and a tail that you would expect to break on impact. Planes are designed with a much lower factor of safety than buildings, i.e. permanent structures like buildings are effectively over-designed typically by a factor of 3, whereas planes are just designed to stay up in the air with relatively little over-design or extra weight. Aluminium is weaker than steel by a ratio of about 3 to 5. To create a plane shaped hole in the building the plane would need to be travelling much faster at a speed comparable to that of the speed of sound in steel (provided the plane does not tear apart while travelling at such speed).
...

... It's just in my nature, I suppose. ...

Well you do self identify as ManiacMatt ManicMatt ...

The whole thing reminds me of the old  "Slowly I Turned" skit
https://www.youtube.com/watch?v=MYP1OBZfFK0

Using your values I get:

Impact force = 26,334 MN (I suspect you've made an error with units).

Apparently fat fingered my calculator.  You got the correct number

I'm not sure about the impact area you've used (which is about 2 m sq). The diagram shown on the Wikipedia page suggests 7.7 m x 9.3 m dimensions for the fuselage cross section. Based on the 3.4 feet (~1 m) steel column spacing, the fuselage cross section area should come in contact with about 40% of steel. So an impact area would be in the order of 7.7 m x 9.3 m x 0.4 = 28 m sq.

The crossection consists of 1/4" thick cylinder and three 4" aluminum slabs to which everything else is attached. One slab runs the length of the fuselage.  The other two run the length of each wing and are tapered at the wing tips.  The interior of the cylinder is composed of air which is not included in the area. The area of the cylinder's edge is about 200sqin but wasn't included as it is an order of magnitude smaller than the area of the slabs.  The only area considered in my calculation are the 4" slabs, which I stand by except that I suppose the cylinder's edge area should be included, eventhough it's not signigificant.     

So impact pressure should be ~ 1000 MPa.

You need to consider the strength values of steel, not the modulus. The ultimate tensile strength of steel is about 500 MPa, and the ultimate shear strength is about 75% of this.

So the ratio of applied pressure to strength is about 2.

I believe the ratio is at least 2 orders of magnitude higher than that.  Even so, using your number the steel tubes would fail, they would shear off as is in the video(s).

Considering Newton's Third Law (every action has an equal and opposite reaction) the impact pressure would also apply to the plane. The ultimate tensile strength of aluminium is 300 MPa, which gives us a ratio of applied pressure to strength of about 3.

It doesn't matter what delivers the force.  It could even be done with water.

Btw, here is a handy stress calculator:
http://www.amesweb.info/StructuralAnalysisBeams/Stresses_Steel_Hollow_Structural_Sections.aspx

[Breakthrough BoyThe Dullest Superhero EverThrough the power of automicity he unconsciously saves the world!]

Sounds like inspiration for an adventure game 

Breakthrough Boy
The Dullest Superhero Ever
Through the power of automicity he unconsciously saves the world!

Congratulations!

.. Really cool, I can't stop watching it.

Hehe ... I think that was my reaction to my first animation way back when. 

WHAM: I disagree.  In either case the person has abandonded his Birtish citizenship and pledged loyalty to enemies who would destroy his home country.  In either case his fellow Birtish citizens would see him as a traitor and would not willing accept him back in thier country except for proseution for treason.  If the Germans won and welcomed him as hero (more likely Hitler would recognize him as traitor and send him off to some shit hole to die a hero's death) then Briton  would no longer exist as an independent country and so there would be no citizenship rights to reclaim.

It doesn't matter if these people are youg and stupid because it's a near certainity that when they return they will deal death and destruction to the loyal Sweedish citizenery.  Looking the other way won't make it any less certain.

The thing you are missing is that they are pledging their allegiance to an ignoble ideology and a group who viciously practice it, to an ideology and group who are at war with the home country.  What they are doing would be the same thing as a British citizen running off to fight for Hitler during WWII.  Neither should retain their citizenship in the country they have betrayed.

The other difference is that these people are not going there to fight for the Iraqi citizens but rather to invade their country.  It's a huge difference isn't it?   

Well, the obvious thing to do is to give them one-way plane tickets to go and don't let them come back to kill you and your fellow citizens.

As far as I remember AGS doesn't have a sprite editor.  Graphics are prepared using other tools such as PS, PSP, GIMP, Paint, Gale, etc.  Sprites and palletes are imported into AGS for use.  I use Graphics Gale for pallette and pixely edits. 

Best advice is to start simple and learn little by little. Just ask for specific help in the Beginners forum. Progress tends to accelerate IMHO.

[Boeing 747 Specifications]

Well the underlying presumption is that according to the laws of physics a comercial jet cannot penetrate hollow steel tubes of which the WTC buildings are constructed.  Well let's do a few quick calculations/approximations.

Boeing 747 Specifications
http://en.wikipedia.org/wiki/Boeing_747
Weight = 833,000 lb, 377,842 kg
Wingspan = 211 ft

Impact Force
http://www.engineeringtoolbox.com/impact-force-d_1780.html
Impact Speed = 264m/s
Impact Force = (0.5(377,842 kg)((264m/s)**2))/0.5m = 30665194560 kN = 6875604161435 lbs

Note: 0.5m slowdown distance is greater than column width.


Impact Area
The plane's super structure is essentially composed of the 4 in aluminum slabs.  One slab within each wing and one lying along the length of the fuselage.  The rest of the plane's structure is air and a 1/4 aluminum shell.  So let's just consider the super structure.

http://911research.wtc7.net/wtc/arch/perimeter.html
The hollow steel columnus on the upper floors were approx 1 ft square and their wass were 1/4" thinck.  They were spaced approcimately 3.4 feet apart.  So over a 211 ft wing span we would expect to have (211/3.4) 62 columns. 

The impact area of of the plane's infrstructure on the columns would be A = (4in)(62x12) = 2976 sqin.

The impact force distributed across that area is Force/Area =  (6875604161435 lbs)/(2976 sqin) = 2310350860 psi (lbs per sqin)

Sheer Modulus of Steel
http://en.wikipedia.org/wiki/Shear_modulus
Sheer modulus is the amount of sheer force that can be applied before steel fails.  I am not certain of the effect of thinckness, however, the columns are only 1/4 in thick. 

Sheer Modulus of Steel = 79Gpa = 11457981 psi

Ratio of Applied Force to Modulus =  2310350860/11457981 psi = 201

According to the crude approximation above the impact force of the plane was 200 times greater than the sheer strength of the hollow columns on the perimiter of the building.  According to the laws of physics a plane penetrating the WTC seems entirely plausible.

Where are Dr Wood's calculations?

Just to followup what Misj said about the radar.  There can be many explanations as to why the radar data is different.  Antenna location, calibration, age and purpose of the radar sets, among other possibilities.   Is there anybody here that seriously expects that the military would reveal to the public just how accurate and percise their capabilities are?  My guess nis that either the data is from an older radar set, or one intended for long range observations, or that the data was modified to obviscate capabilities. 

In any case, both radars tracked solid and massive objects along similar paths which ended when the "supposed" plane struck the building. Being scientific and all if the object or objects didn't strike the building then one would have to an alternative explaination of how their mass and momentum  were dissipated.  Oh yeah, I forgot about the energy beam weapon.  Guess that just proves the existence of the weapon.

[Aliens]

Not that it matters but here are some facts:

Aliens
Yup.  Aliens!


Airplane Wings
Each wing is made from a solid piece of aluuminum ~5 inches thick at the fuselage end and 1-2 inches thick at the tip.  The Davenport Iowa, Alcoa Aluminum factory makes them for Boeing.  I had several projects in this factory, over a period of several years, and walked by the NC milling machine that cut these out of a solid aluminum plate.  Ribs, skin, and other parts, I was told, are attached to the solid aluminum substructure. Here is a satelite view of the  Alcoa factory

WTC Construction
The Minerals, Metals & Materials Society have a good description of the WTC towers' construction.  You can read the full article here.  Here are a few facts from the article.

The towers were designed and built in the mid-1960s through the early 1970s. They represented a new approach to skyscrapers in that they were to be very lightweight.  Modular construction methods were used (i.e. lots of bolts)

A lightweight “perimeter tube” design was used (i.e. 36 cm square steel tube, able to support weight but not so much lateral impact)


Web joists 80 cm tall connected the core to the perimeter at each story (i.e. to support a concrete floor).


The building is an egg-crate construction that is about 95 percent air.

 
The example about relativity misses the point but comes to the right conclusion anyway.  Relativity is a simpler and less convoluted theory of how time, space and matter work than is Newton's theory. Newton's theory seems to be simpler on the surface because it leaves a lot of things without explanation.  If one were to "patch" Newton's theory so that it explained everything as well as Relativity it would become extremely convoluted and complex.

There is a difference between complexity and difficulty.  For example Newton's theory is expressed using basic algebra and Einstein's theory is expressed using advanced calculus.  While it's true that algebra is easier to understand than calculus, it is not true that algebraic expressions are always less complex than ones represented in calculus.  In fact, quite often the opposite is true (anyone who studied electro-magnetic wave theory knows this). 

Applying Occam's Razor to model accuracy, as described in the link, is misguided IMHO.  It seems folks are conflating accuracy and correctness.  Newton's model is incorrect, as shown by the behavior of Mercury, not just inaccurate.  Creating a mathematical expressions to fit a given data set may be referred to as a model but it can only be characterized in terms of accuracy and not in terms of correctness.

The linked article identifies three sources Exit Signs on the aircraft, time pieces, and scope mon gov weapons stored at the site.

Monkey, the article about the court case you linked says that it was dismissed. This means that the party bring suit failed to show that they had legal standing or failed to show the slightest chance of prevailing. 

As I pointed out in my earlier post concrete disintegrates into powser when heated to 1200F.  It weakens long before that as the different materials it is comprised of have different thermal expansion coefficients.  You can test this yourself; just take a blow torch to any random concrete sidewalk and see how much time passes before chips start flying off in all directions.  A 747 holds about 40,000 gallons of jet fuel that burns at 1800F.

In the interview Dr Wood doesn't want to talk about her own assertions.  She doesn't want to talk about the magnitude of particle beam energy rerquired to do what she says it did.  She wave her hands around and says it's not important when it's plain and obvious that it is important.  She seem to me to be an incoherent nincompoop.

https://uk.answers.yahoo.com/question/index?qid=20110315120912AAtbCUr

Concrete does not burn, but somewhere around 1200 degrees it will produce steam to become calcium oxide.

Ca(OH)2 -> CaO + H2O

Calcium oxide is a white powder which melts at nearly 3000 C.
Source(s):
I'm a chemist!
Roger S · 4 years ago

It's my understanding that the towers were built with a concrete core that housed the elevators and utilities and that also carried a good portion of the vertical load. The combustion of the jet fuel heated the concrete enough to fail and the weight of the building did the rest.