Merged 9/11 CT subforum General Discussion Thread

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alexi_drago said:
I quickly worked out a rough value of about 11 cm/s which isn't too far off .35 ft/s but it's assuming an awful lot about the collision that wouldn't be the case.
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To move a building at that speed is indicative of a 1300 to 2000 pound of TNT kinetic energy impact. Too bad bullets don't just move us along slowly instead of ripping through our bones and killing us.

What is his purpose? What is his goal and conclusions? So far all he does is spread lies about 911 all over the Internet.
 
beachnut said:
What is his purpose? What is his goal and conclusions? So far all he does is spread lies about 911 all over the Internet.
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I would be interested to know if he (or any CTist) EVER posts anything other than self-deluding nonsense

As this seems highly unlikely, I'm unsubscribing from this thread
 
six7s said:
I would be interested to know if he (or any CTist) EVER posts anything other than self-deluding nonsense

As this seems highly unlikely, I'm unsubscribing from this thread
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1. Welcome back...keep yourself on this side of the suspension sod if you can. ;)

2. This is the general discussion thread, so no one topic is covered here. It would be a shame for you to ignore or not post within.

TAM:)
 
I figure if I'm not lazy I'll start doing a quote of the week like this. Yeah yeah I know Gravy and a number of others have compiled a number of witness statements, more than enough to put CT's in their place... but I like pushing buttons:

http://www.archive.org/details/abc200109110954-1036

The reporter in this footage is often quoted for this by CT's:
"The second building that was hit by the plane just completely collapsed. The entire building has just collapsed, just as if a demolition team set off..."( Quote continues on from here)

Above starts at 5:20

Later on he gives his opinion:

"...what appeared to happen from my vantage point was the top part of the building was totally involved in fire and there appeared to be no effort possible to put that fire out. It looked like the top part of the building was so weakened by the fire that it just, the weight of it collapsed the rest of the building. That's what appeared to happen. I did not see anything happen at the base of the building. It all just appeared to start at the top and collapse all of the rest of the building by the sheer weight of the top... there was no explosion or anything at the base part of it.... " (quote continues on in the video)
(TIME -- 7:30-8:00)

Notice truthers who like to cherry-pick... the difference between a metaphor/simile and their actual opinion
 
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Does anybody think that FEMA was being misleading by putting this graphic in their official report ? This depicts a 747 going through the core columns. Can anybody speculate why they would have used a lane for the graphic that is twice the size of a 767 ? Could they not just as easiiy have depicted a far smaller 767 ?



Figure 5 (from the study). Results of simulation analysis of impact of a 747 jetliner crashing into a steel structure. Notice fracture of the steel column and breaking of the plane due to dynamic stresses (Graphics and analysis by MSC Software Corporation).
 
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bill smith said:
Does anybody think that FEMA was being misleading by putting this graphic in their official report ? This depicts a 747 going through the core columns. Can anybody speculate why they would have used a lane for the graphic that is twice the size of a 767 ? Could they not just as easiiy have depicted a far smaller 767 ?

Figure 5 (from the study). Results of simulation analysis of impact of a 747 jetliner crashing into a steel structure. Notice fracture of the steel column and breaking of the plane due to dynamic stresses (Graphics and analysis by MSC Software Corporation).
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1. Those aren't "the core columns" of WTC, they're "a steel structure".

2. NIST perform a massive analysis of theoretical core column damage from an increasingly shredded aircraft, that is of much more value. Why are you raising the FEMA study for discussion?

In fact why are you asking all these questions about "WTC moving at 600mph and hitting a stationary aircraft" at all? What is the value?
 
bill smith said:
This stuff is fascinating. I've been watching one or two of Walter Lewin's lectures I'll have to take time with this though. hanks for the info. How would you write this in scientific notation incidentally ?

''and its final velocity is the velocity of the airliner, multiplied by the mass of the airliner, divided by the sum of the two masses''
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Vf = Va x Ma / (Ma + Mb),

where,

Vf is the final velocity of the composite structure,
Va is the initial velocity of the airliner,
Ma is the mass of the airliner, and
Mb is the mass of the building.

In this case we set the initial velocity of the building to zero. A more general case is,

Vf = [(Va x Ma) + (Vb x Mb)] / (Ma + Mb),

where Vb is the initial velocity of the building; however, since all the velocities are vectors (which is why they're in bold type), in this case the final velocity comes from a vector sum; you need to choose a set of x, y and z axes, calculate the component of velocity parallel to each axis, and add them separately. That isn't necessary in the case where either the building or the airplane is initially stationary, because the initial and final velocity must be in the same direction.

This all assumes that the collision is perfectly inelastic. That's not exactly true, but it's a good enough starting approximation in this case.

Dave
 
Dave Rogers said:
Vf = Va x Ma / (Ma + Mb),

where,

Vf is the final velocity of the composite structure,
Va is the initial velocity of the airliner,
Ma is the mass of the airliner, and
Mb is the mass of the building.

In this case we set the initial velocity of the building to zero. A more general case is,

Vf = [(Va x Ma) + (Vb x Mb)] / (Ma + Mb),

where Vb is the initial velocity of the building; however, since all the velocities are vectors (which is why they're in bold type), in this case the final velocity comes from a vector sum; you need to choose a set of x, y and z axes, calculate the component of velocity parallel to each axis, and add them separately. That isn't necessary in the case where either the building or the airplane is initially stationary, because the initial and final velocity must be in the same direction.

This all assumes that the collision is perfectly inelastic. That's not exactly true, but it's a good enough starting approximation in this case.

Dave
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Vf is the final velocity of the composite structure,
Va is the initial velocity of the airliner,
Ma is the mass of the airliner, and
Mb is the mass of the building.

(I used tons and mph).
So if....
Vf = Va x Ma / (Ma + Mb)
Then...
590 x 150 / (150+500.000) = 88.500 / 500.150) = 0.176946916
Vf = 0.176946916 (mph ?)

Is this right ?
 
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bill smith said:
Vf is the final velocity of the composite structure,
Va is the initial velocity of the airliner,
Ma is the mass of the airliner, and
Mb is the mass of the building.

(I used tons and mph).
So if....
Vf = Va x Ma / (Ma + Mb)
Then...
590 x 150 / (150+500.000) = 88.500 / 500.150) = 0.176946916
Vf = 0.176946916 (mph ?)

Is this right ?
Click to expand...

Yes, for the starting numbers you've used. In this case the units aren't an issue because they cancel out, so mph and tons is OK; be careful about mixing units in any more complex calculation, though; in general it's best to convert everything into kilogrammes, metres and seconds (I've made one or two real howlers here as a result of failing to do that). I think the best value for the mass of the building is rather lower - about 280,000 tons rings a bell - but your maths is fine.

That'll give you an estimate of how fast the building recoils in the first instant after impact. As soon as it starts to move, the elasticity of the structure then opposes the motion, so you have to start calculating the elastic response of the building. That gets very complicated very quickly; ask a structural engineer for help with that one.

Dave
 
bill smith said:
Vf is the final velocity of the composite structure,
Va is the initial velocity of the airliner,
Ma is the mass of the airliner, and
Mb is the mass of the building.

(I used tons and mph).
So if....
Vf = Va x Ma / (Ma + Mb)
Then...
590 x 150 / (150+500.000) = 88.500 / 500.150) = 0.176946916
Vf = 0.176946916 (mph ?)

Is this right ?
Click to expand...

Assume a perfectly spherical and rigid World Trade Center :):)

I applaud Bill's interest in the physics of the problem.
 
Dave Rogers said:
Yes, for the starting numbers you've used. In this case the units aren't an issue because they cancel out, so mph and tons is OK; be careful about mixing units in any more complex calculation, though; in general it's best to convert everything into kilogrammes, metres and seconds (I've made one or two real howlers here as a result of failing to do that). I think the best value for the mass of the building is rather lower - about 280,000 tons rings a bell - but your maths is fine.

That'll give you an estimate of how fast the building recoils in the first instant after impact. As soon as it starts to move, the elasticity of the structure then opposes the motion, so you have to start calculating the elastic response of the building. That gets very complicated very quickly; ask a structural engineer for help with that one.

Dave
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Thanks for the tutorial Dave. I could get into this easily. One other question about this one.
How would you write it if the building was moving towards the plane at 590 mph ?
 
bill smith said:
both of them converging at 590 each..sorry
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I pnly ask this question because I think the answer should be Vf = 589.823053. But my calculator gives me 590 or -590 depending on whether I enter the 590 as a plus or a minus in the formula.
 
bill smith said:
I pnly ask this question because I think the answer should be Vf = 589.823053. But my calculator gives me 590 or -590 depending on whether I enter the 590 as a plus or a minus in the formula.
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If they're converging, then the directions are opposite, so you can treat it as a one-dimensional problem with the momentum of the airliner being negative. Therefore, subtract the airliner momentum from the building momentum, and divide the result by the total mass.

Vf = [(590 x 500000) - (590 x 150)]/500150

However, that won't give you 589.823 (which is, of course, 590mph less the final velocity with the building stationary) because you've doubled the relative velocity by having both moving at 590mph. If you want to work out the case for both moving at the same speed, but keep the same impact velocity, use 295mph for the building and -295mph for the airliner, and you'll get the result you're looking for.

Dave
 
Dave Rogers said:
If they're converging, then the directions are opposite, so you can treat it as a one-dimensional problem with the momentum of the airliner being negative. Therefore, subtract the airliner momentum from the building momentum, and divide the result by the total mass.

Vf = [(590 x 500000) - (590 x 150)]/500150

However, that won't give you 589.823 (which is, of course, 590mph less the final velocity with the building stationary) because you've doubled the relative velocity by having both moving at 590mph. If you want to work out the case for both moving at the same speed, but keep the same impact velocity, use 295mph for the building and -295mph for the airliner, and you'll get the result you're looking for.

Dave
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Okay...I understand most of that. I can see that once you are familiar with the terms and concepts you can almost read it like text. An awful lot to learn though. Thanks again.
 
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