9-11 Presentation at NMSR, May 19 2010

AZCat said:
ergo said:
Describe to us where in the video evidence of the Twin Towers' collapses we see the effects of conservation of momentum in action.
Everywhere. It would be far more noteworthy if there were evidence that momentum were not being conserved.

Juxtaposing your two "independent" answers for comedic effect:

Um... Everywhere. I don't think that conservation of momentum was ever violated in the collapse - if you think that it was, you are free to point out when and where and support your argument with calculations. Somehow I doubt you'll do that.

"Everywhere", eh? And you "don't think" it was violated? But you're not sure.

Why don't we look at it this way: tell me how you think conservation of momentum would express itself in the WTC collapses.

The collapse starts in the impact zone and moves downwards - you know, one floor at a time (rather than all at once).

If it was one floor at a time, we would be seeing a bump, crush, bump, crush, bump, crush effect. If it was one floor at a time, well, crush-down would never complete, but if somehow it had the energy to, it would take much much longer than we see.

Yes, one floor of the upper block hits one floor of the lower block

each crushing the other, as would be predicted by Newton's Third Law.

after which both floors

as rubble,

move together according to conservation of momentum.

No, according to gravity. Well, OK, in your model, yes.

Since they are still moving, this puts strain on the columns below

No, because rubble can't really do much to the columns.

to dissipate the energy and stop the impacted floors

rubble, you mean,

Since the impacted floors rubble are is now moving slower than the rest of the upper block, strain is also placed on the columns above the impact.

As it has been doing from the beginning.

Assuming that they don't reach their elastic limit, they transmit that strain to the columns below

Which they have been doing from the beginning, and which the lower columns have also been opposing, from the beginning

resulting in much more stress being placed on the lower columns than is placed on the upper columns

according to the physical laws of Fantasy Unicorn Land? No. That's not how Newton's Third Law works.

thus they fail first (crush down)

Wrong.

and the columns above fail later (crush up).

Wrong, both in theory and in reality. Crush up clearly occurs before any crush down could have begun.

If you look at it from the point of view of the necessary conditions for building survival, then all of the 1.36 gigaJoules of kinetic energy must be dissipated in order for the upper block to stop moving - the lower block must do the lion's share of this work

1.36 gigjoules of energy being opposed by the larger, stronger, more intact lower floors, yes. When a force is applied, that force is met by an equal and opposite force. In this case, not even equal, as the lower block is in much better position to withstand anything the smaller, weaker, lighter, burnt-up upper block could deliver.

with the structure of the building misaligned due to the collapsed story storeys
on both sides, yes. Much harder for the upper block to do the crushing it wants to do.

(plus damage due to the jet impact).

Um, that's what was crushed through in the beginning. Remember?

There's no way that those columns could avoid failing and they are the ones that we would expect to fail first.

Yes, the columns in both the upper and lower blocks could fail in that kind of impact (if we're talking about a "drop", which we never really are, because something that large doesn't "drop" through the remaining 85% columns in the impact zone - but never mind that for now).
Both upper and lower structures would suffer damage in that impact zone. The lower ones would most certainly not fail first. For one thing, the columns in the lower sections of the building were thicker, but even if we assume they are equal in the upper portion of the building where collapse began, why would you guess they would fail first? With what do you support this claim?

Thank you for comparing me to an outstanding engineer. The math of the collapse is inescapable. The upper block goes from something only a couple of times too big for the lower block to stop to the hand of god very quickly.

The lower block is the larger, heavier, more intact structure. So no, in this case, the upper block is never "too big" for it.

It is patently obvious that if the first floor can't arrest the collapse, then no floor will be able to.

Neither of our first floors in either the upper or lower blocks survived, according to Newton's Third Law. Remember?

The highest intact floor must absorb the kinetic energy and transmit it to the structure below in order for the building to survive - the amount of energy that it is being asked to conduct is well above the amount of energy the columns are able to handle.

In both upper and lower blocks.

Thus they fail.

Yes, according to Newton's Third Law.

It is possible to estimate the yield strength of the lower block columns - calculate it and tell me how those columns can possibly absorb and transmit 1.36 gigaJoules.

As noted above, being larger, stronger, and being able to transmit that energy right back into the upper block, as per Newton's....you get the idea.

Show what each of us has written to any physicist (or structural engineer) and see which one makes him burst out laughing...

Sure. Go ahead.
 
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I see you're laboring under the same misconception as Tony Szamboti - that the upper portion must decelerate in order to apply a force. This is incorrect.
Please explain how this is incorrect.
Demonstration:
  1. Purchase a bathroom scale.
  2. Stand on it.
  3. Let the indicated weight stabilize.
When the indicated weight stabilizes, you are not decelerating, but you're still applying a downward force. If you weren't applying a downward force, your indicated weight would be zero.

A more interesting demonstration:
  1. Purchase a bathroom scale.
  2. Find a tall building.
  3. Take an elevator to one of the top floors.
  4. Remain inside the elevator, but stand on the scale.
  5. Take the elevator down to the ground floor.
  6. Observe the weight indicated by the scale.
As the elevator begins its descent, your indicated weight decreases but does not go all the way to zero. That means you are still applying a downward force to the scale, even though you are still accelerating downwards. QED.

At some point, the elevator will begin to slow. From there to the bottom, you will be accelerating upwards, i.e. decelerating downwards, and your indicated weight will be greater than your normal weight. That part of your elevator ride is not part of the demonstration.

When you get this Newtonian physics thing figured out, please explain it to Tony.
 
Demonstration:
  1. Purchase a bathroom scale.
  2. Stand on it.
  3. Let the indicated weight stabilize.
When the indicated weight stabilizes, you are not decelerating, but you're still applying a downward force. If you weren't applying a downward force, your indicated weight would be zero.

Lol. You must go through a lot of bathroom scales... how ever could they oppose the gravitational pull of your massive mass ?!?
 
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Please explain how scale affects conservation of momentum.

You didn't even bother to watch the EXCELLENT video explaining the physics of 911, which discusses how scale affects any modeling attempts... and even discusses the conservation of momentum... tsk tsk tsk.

so we know you
a. don't know how to use a stopwatch
b. don't understand how rubble/ loose particles work
c. are incapable of providing any citations to other peoples works beyond "others have done the work" Ie argument from incredulity
d. are incapable of watching a video on youtube (unless it is a truther video)
e. and completely and utterly don't understand scale.
 
Please explain how this is incorrect.

Guess what? Structural members are also subject to Newton's Third Law. What scale model are you talking about? A miniature Twin Tower? Both a model and the WTC are subject to conservation of momentum.

You haven't explained how scale would change how conservation of momentum is expressed.

What explanations? You haven't provided any.

Evasion noted. Still can't muster up an answer, eh?

do you intend to watch the video this time? You might just learn something.



Now try to watch it... take some notes and then tell me what mackey has wrong...
 
Please explain how this is incorrect.
See W.D. Clinger's above post for a succinct explanation.

Guess what? Structural members are also subject to Newton's Third Law. What scale model are you talking about? A miniature Twin Tower? Both a model and the WTC are subject to conservation of momentum.
We can generalize it for any model.

You haven't explained how scale would change how conservation of momentum is expressed.
It is clear you misunderstand the whole concept here. It isn't just about conservation of momentum - it's about dynamic similitude.

What explanations? You haven't provided any.
Yes, I have. Here is what I previously said:
AZCat said:
Because the forces seen by structural members in the model and in the original are a function of mass and cross-section, and those two properties do not scale the same. Mass scales as a function of the cube of the scale factor, and cross-section scales as a function of the square, therefore a scale model of the WTC towers will not have dynamic similitude.
Although it should be noted that I should have said "stresses" rather than "forces".

Evasion noted. Still can't muster up an answer, eh?
It's an answer, just one that you apparently can't understand.
 
Describe to us where in the video evidence of the Twin Towers' collapses we see the effects of conservation of momentum in action.

Originally Posted by Slartibartfast
Um... Everywhere. I don't think that conservation of momentum was ever violated in the collapse - if you think that it was, you are free to point out when and where and support your argument with calculations. Somehow I doubt you'll do that.
"Everywhere", eh? And you "don't think" it was violated? But you're not sure.

It's a figure of speech - I'm sure. But if you think that conservation of momentum was violated, please present evidence of that to us (and the Nobel committee).

Why don't we look at it this way: tell me how you think conservation of momentum would express itself in the WTC collapses.


Momentum would be conserved in every collision that occurred in the WTC collapse (it would also be conserved between the building/rubble and the Earth).

The collapse starts in the impact zone and moves downwards - you know, one floor at a time (rather than all at once).
If it was one floor at a time, we would be seeing a bump, crush, bump, crush, bump, crush effect. If it was one floor at a time, well, crush-down would never complete, but if somehow it had the energy to, it would take much much longer than we see.

I disagree. Prove it. I'll be happy to supply the math that proves my argument after you have done the same.

Yes, one floor of the upper block hits one floor of the lower block
each crushing the other, as would be predicted by Newton's Third Law.

The question is, how are the two floors stopped? While a little bit of the concrete is pulverized, most of it is still there along with the steel - what provides the force to stop that mass from moving? (or move it outside of the footprint of the building)

after which both floors
as rubble,

So the collision is powerful enough to turn two floors into 'rubble' which magically allows all of that mass to 'flow' to the side? Are you really that ignorant of physics or do you just refuse to admit the truth because you know your theories are rationally indefensible?


move together according to conservation of momentum.
No, according to gravity. Well, OK, in your model, yes.

Exactly what form do you think the 'rubble' of the two impacted floors is in? And how fast is it going after impact? Gravity is what accelerates the upper block between floors - conservation of momentum determines what the velocity of the floors after impact is (not in 'my model', but in reality).



Since they are still moving, this puts strain on the columns below
No, because rubble can't really do much to the columns.

What you're saying is that the columns can't do much to stop the rubble (a large, moving mass of concrete and steel) from continuing downward and shredding the building as it goes.


to dissipate the energy and stop the impacted floors
rubble, you mean,

You apparently don't understand that rubble is worse than an intact floor - the building is not designed to exert force on rubble...

Since the impacted floors rubble are is now moving slower than the rest of the upper block, strain is also placed on the columns above the impact.
As it has been doing from the beginning.

There is no strain on the columns of the upper block while it is in free-fall.


Assuming that they don't reach their elastic limit, they transmit that strain to the columns below
Which they have been doing from the beginning, and which the lower columns have also been opposing, from the beginning

the lower block stopped being able to exert sufficient force on the upper block - that's what the initiating event was.


resulting in much more stress being placed on the lower columns than is placed on the upper columns
according to the physical laws of Fantasy Unicorn Land? No. That's not how Newton's Third Law works.

Can you calculate the stress on the upper and lower columns? I can. And basic physics tells me that the stress on the lower columns will be greater than the stress on the upper columns. I'm beginning to doubt that you know how any physical laws work...


thus they fail first (crush down)
Wrong.

And you know this based on your detailed knowledge of physics and the extensive calculations you've done?


and the columns above fail later (crush up).
Wrong, both in theory and in reality. Crush up clearly occurs before any crush down could have begun.

I assume your highly trained physical intuition tells you this...


If you look at it from the point of view of the necessary conditions for building survival, then all of the 1.36 gigaJoules of kinetic energy must be dissipated in order for the upper block to stop moving - the lower block must do the lion's share of this work
1.36 gigjoules of energy being opposed by the larger, stronger, more intact lower floors, yes. When a force is applied, that force is met by an equal and opposite force. In this case, not even equal, as the lower block is in much better position to withstand anything the smaller, weaker, lighter, burnt-up upper block could deliver.

So you don't think there is a difference between a heavyweight boxer putting his glove against your chest and pushing as hard as he can versus him pulling his arm back and punching you? The building wasn't designed to exert force against a moving upper block - no building is.


with the structure of the building misaligned due to the collapsed story
storeys
on both sides, yes. Much harder for the upper block to do the crushing it wants to do.

The upper block wants to keep moving down (maybe you've heard that an object in motion tends to stay in motion) and the lower block is less able to do anything about it.


(plus damage due to the jet impact).
Um, that's what was crushed through in the beginning. Remember?

I'm saying that the floor trying to 'catch' the collapse was not an intact floor, but one that had already been damaged by the jet impact. The impact damage spanned several floors, remember?


There's no way that those columns could avoid failing and they are the ones that we would expect to fail first.
Yes, the columns in both the upper and lower blocks could fail in that kind of impact (if we're talking about a "drop", which we never really are, because something that large doesn't "drop" through the remaining 85% columns in the impact zone - but never mind that for now [Clearly you're saving up for a massive physics 'fail' here...]).
Both upper and lower structures would suffer damage in that impact zone. The lower ones would most certainly not fail first. For one thing, the columns in the lower sections of the building were thicker, but even if we assume they are equal in the upper portion of the building where collapse began, why would you guess they would fail first? With what do you support this claim?

With physics and math. What do you support your claims with besides ignorance and wishful thinking?


Thank you for comparing me to an outstanding engineer. The math of the collapse is inescapable. The upper block goes from something only a couple of times too big for the lower block to stop to the hand of god very quickly.
The lower block is the larger, heavier, more intact structure. So no, in this case, the upper block is never "too big" for it.

Conservation of energy says otherwise.

It is patently obvious that if the first floor can't arrest the collapse, then no floor will be able to.
Neither of our first floors in either the upper or lower blocks survived, according to Newton's Third Law. Remember?

To restate (since you seem to reach for semantic arguments when you're grasping at straws..), if the collapse isn't arrested after the first impact then it will never be arrested because the subsequent impacts are even less favorable to building survival than the first.


The highest intact floor must absorb the kinetic energy and transmit it to the structure below in order for the building to survive - the amount of energy that it is being asked to conduct is well above the amount of energy the columns are able to handle.
In both upper and lower blocks.

Because the floors are moving at different speeds after impact, more stress will be placed on the columns of the lower block.


Thus they fail.
Yes, according to Newton's Third Law.

How exactly are you applying Newton's third law? Because it sounds like you are trying to use a buzzword to make your argument sound somehow reasonable and instead betraying an ever-increasing ignorance of physics.


It is possible to estimate the yield strength of the lower block columns - calculate it and tell me how those columns can possibly absorb and transmit 1.36 gigaJoules.
As noted above, being larger, stronger, and being able to transmit that energy right back into the upper block, as per Newton's....you get the idea.

Yeah, I get the idea. You are profoundly ignorant when it comes to basic physics.

Show what each of us has written to any physicist (or structural engineer) and see which one makes him burst out laughing...
Sure. Go ahead.

That was a suggestion for you to do - I already know that I'm right here. I was just hoping that you would have the intellectual honesty to seek out an impartial person to confirm if your really as smart as you think you are or if there are turnips with a higher IQ. You know, in a way you're very comforting - as long as there are people like you in the 9/11 truthiness movement no one has to worry that it will ever be taken seriously by anyone rational.
 
The upper block wants to keep moving down (maybe you've heard that an object in motion tends to stay in motion) and the lower block is less able to do anything about it.

if the collapse isn't arrested after the first impact then it will never be arrested because the subsequent impacts are even less favorable to building survival than the first.

Because the floors are moving at different speeds after impact, more stress will be placed on the columns of the lower block.
It looks like you are applying 1D model behaviours literally. There are a couple of recent threads on this point wrt Bazant et al.
 
Demonstration:
  1. Purchase a bathroom scale.
  2. Stand on it.
  3. Let the indicated weight stabilize.
When the indicated weight stabilizes, you are not decelerating, but you're still applying a downward force. If you weren't applying a downward force, your indicated weight would be zero.

A more interesting demonstration:
  1. Purchase a bathroom scale.
  2. Find a tall building.
  3. Take an elevator to one of the top floors.
  4. Remain inside the elevator, but stand on the scale.
  5. Take the elevator down to the ground floor.
  6. Observe the weight indicated by the scale.
As the elevator begins its descent, your indicated weight decreases but does not go all the way to zero. That means you are still applying a downward force to the scale, even though you are still accelerating downwards. QED.

At some point, the elevator will begin to slow. From there to the bottom, you will be accelerating upwards, i.e. decelerating downwards, and your indicated weight will be greater than your normal weight. That part of your elevator ride is not part of the demonstration.

When you get this Newtonian physics thing figured out, please explain it to Tony.

I only have high school physics and I can understand that,Why can't you Ergo? Have you ever had any physics lessons?
 
I only have high school physics and I can understand that,Why can't you Ergo? Have you ever had any physics lessons?


Well, this is the same guy that isn't sure that ruble the weight of the chucklef:Dking moon dropped from 12 feet up would crush the towers, so....yeah.
 
The question is, how are the two floors stopped? While a little bit of the concrete is pulverized, most of it is still there along with the steel - what provides the force to stop that mass from moving? (or move it outside of the footprint of the building)

Um, the intact rest of the building. What part of this don't you understand?

after which both floors
as rubble,

So the collision is powerful enough to turn two floors into 'rubble' which magically allows all of that mass to 'flow' to the side? Are you really that ignorant of physics or do you just refuse to admit the truth because you know your theories are rationally indefensible?

You say the collision "isn't powerful enough" to turn the two colliding floors into rubble, but it is powerful enough to generate a complete collapse of the rest of the intact building. WTF. This is your "physics"? Sorry, this is a completely asinine statement to make.

Furthermore, we have not even begun to discuss the rubble ejecting from the sides, so why are you bringing this up now? To deflect the argument? I was following the sequence of events YOU provided, and we are not yet discussing the loss of mass.

Since they are still moving, this puts strain on the columns below
No, because rubble can't really do much to the columns.
What you're saying is that the columns can't do much to stop the rubble (a large, moving mass of concrete and steel) from continuing downward and shredding the building as it goes.

Yes, the rubble is "shredding" the building. LOL.

to dissipate the energy and stop the impacted floors
rubble, you mean,
You apparently don't understand that rubble is worse than an intact floor - the building is not designed to exert force on rubble...

Please explain how rubble is "worse" than an intact floor. And, if the building can exert force on an intact block, how can it not be exerting force on rubble? I don't really believe you have no clue what you're talking about, but you do present that way.

Since the rubble are is now moving slower than the rest of the upper block, strain is also placed on the columns above the impact.
As it has been doing from the beginning.

There is no strain on the columns of the upper block while it is in free-fall.

Please explain how the upper block "free falls" through the 85% remaining columns in the impacted floors.

the lower block stopped being able to exert sufficient force on the upper block - that's what the initiating event was.

Wow. How did it stop being able to exert sufficient force, Mr. Fantasy Unicorn Land?

And basic physics tells me that the stress on the lower columns will be greater than the stress on the upper columns. .

Please explain how this would be true and be in accord with Newton's Third Law. This is basic physics.

and the columns above fail later (crush up).
Wrong, both in theory and in reality. Crush up clearly occurs before any crush down could have begun.
I assume your highly trained physical intuition tells you this...

No, the photos tell us this, for those of us interested in looking at what actually happened, instead of what we wish happened.

Please indicate where the upper block is seen through the collapse progression.

1.36 gigjoules of energy being opposed by the larger, stronger, more intact lower floors, yes. When a force is applied, that force is met by an equal and opposite force. In this case, not even equal, as the lower block is in much better position to withstand anything the smaller, weaker, lighter, burnt-up upper block could deliver.

So you don't think there is a difference between a heavyweight boxer putting his glove against your chest and pushing as hard as he can versus him pulling his arm back and punching you? The building wasn't designed to exert force against a moving upper block - no building is.

No building is designed to exert force against a moving upper block?? In fact, most highrises are. Most natural collapses are partial. There was also no "drop" of any upper block. If you disagree with this, show us the visual evidence.

The upper block wants to keep moving down (maybe you've heard that an object in motion tends to stay in motion)

yes, unless acted on by another force. Did you forget that part?

and the lower block is less able to do anything about it.

The lower block is "less able"? to "do anything about it"? According to what physical law? This is getting too stupid to comment to.

(plus damage due to the jet impact).
Um, that's what was crushed through in the beginning. Remember?
I'm saying that the floor trying to 'catch' the collapse was not an intact floor, but one that had already been damaged by the jet impact. The impact damage spanned several floors, remember?

:boggled: Both colliding floors were damaged.


Both upper and lower structures would suffer damage in that impact zone. The lower ones would most certainly not fail first. For one thing, the columns in the lower sections of the building were thicker, but even if we assume they are equal in the upper portion of the building where collapse began, why would you guess they would fail first? With what do you support this claim?

With physics and math.

No, you haven't. You regurgitate Bazant, whose math has already been show to be incorrect. You make no attempt to support your assertions or describe how they would be supported by accepted physical principles.

The lower block is the larger, heavier, more intact structure. So no, in this case, the upper block is never "too big" for it.

Conservation of energy says otherwise.

Wow. Please explain to us how conservation of energy says otherwise. :rolleyes:

It is patently obvious that if the first floor can't arrest the collapse, then no floor will be able to.
Neither of our first floors in either the upper or lower blocks survived, according to Newton's Third Law. Remember?
To restate (since you seem to reach for semantic arguments when you're grasping at straws..), if the collapse isn't arrested after the first impact then it will never be arrested because the subsequent impacts are even less favorable to building survival than the first.

Merely repeating this doesn't make it true. This is Bazant's "inevitability" argument. It is not true in real life, nor is it true in theory. Moreover, you brush over the fact that both colliding floors are now crushed or severely damaged.

Impact is absorbed both ways. What part of this don't you understand?

The highest intact floor must absorb the kinetic energy and transmit it to the structure below in order for the building to survive - the amount of energy that it is being asked to conduct is well above the amount of energy the columns are able to handle.
In both upper and lower blocks.

Because the floors are moving at different speeds after impact, more stress will be placed on the columns of the lower block.

How are the two crushed floors moving at different speeds? They're both crushed between the supposed upper block and the lower block. Gravity is acting on them, pulling them against the intact lower block. HOW are the two crushed floors moving at different speeds? This is *********** idiotic.

Arguing with idiots is a waste of time. What we need to do is get "debunkers" up in a public arena, explaining their idiotic theories to mainstream America. Don't discuss thermite. Don't discuss CD. Discuss the official collapse theory. THEN we will begin to see the general inertia of ignorance changing. The only reason this explanation has lasted as long as it has is because most people don't understand what exactly is being proposed, and they don't have the time to care. Most people's understandings, I would guess, are still based on notions of pancaking.

Thus they fail.
Yes, according to Newton's Third Law.
How exactly are you applying Newton's third law? Because it sounds like you are trying to use a buzzword to make your argument sound somehow reasonable and instead betraying an ever-increasing ignorance of physics.

If you understood Newton's Third Law, you would understand that the two colliding floors would be exerting the same force on each other. But you don't, so that's why you had to ask this question.

It is possible to estimate the yield strength of the lower block columns - calculate it and tell me how those columns can possibly absorb and transmit 1.36 gigaJoules.

As noted above, being larger, stronger, and being able to transmit that energy right back into the upper block, as per Newton's....you get the idea.

Whatever the upper block is able to deliver, the lower block can transmit back, because they are both of the same material and construction, with, actually, the lower block being stronger as you progress lower.
 
It looks like you are applying 1D model behaviours literally. There are a couple of recent threads on this point wrt Bazant et al.
... looks like you are exposing your lack of engineering skills. Can't you help the guy support his failed physics into some conspiracy theory with a model or some evidence?


... Whatever the upper block is able to deliver, the lower block can transmit back, because they are both of the same material and construction, with, actually, the lower block being stronger as you progress lower.
Ergo, ergo no buildings can fall! No matter how much the fire destroys the building it stands. Good job making the WTC into the Titanic.

You apply delusional physics and can't comprehend reality. You never had physics.

You are applying Heiwa's law of stupid physics. No building can fall due to anything; we have super building! lol

Robertson, the chief structural engineer for the WTC towers said the buildings fell due to impacts and fires. He designed the building to stop impacts of aircraft at 200 mph, but on 911 the impacts were 7 and 11 times more kinetic energy than his design! The fires were massive and destroyed the WTC. You don't have a practical knowledge of physics and prove it on every post.

... Whatever the upper block is able to deliver, the lower block can transmit back, because they are both of the same material and construction, with, actually, the lower block being stronger as you progress lower.
Why car crashes never destroy the cars, they are both the same material! Wow, no more car crash damage! No more totaled cars using ergo-super-physics for 911 truth.
 
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I only have high school physics and I can understand that,Why can't you Ergo? Have you ever had any physics lessons?


I haven't even taken physics and I understood it perfectly and why its true. why? BECAUSE we did this experiment in HIGH School to understand gravity.
 
Um, the intact rest of the building. What part of this don't you understand?

If the floor the pieces hit fails, it's not going to stop anything. Before the "intact rest of the building" can stop the upper block, it has to fall to that floor's surface. And if the topmost floor failed, why would the floor below be better able to withstand a larger mass falling the same distance?

You say the collision "isn't powerful enough" to turn the two colliding floors into rubble, but it is powerful enough to generate a complete collapse of the rest of the intact building. WTF. This is your "physics"? Sorry, this is a completely asinine statement to make.

Oh no, both floors will likely be reduced to rubble. I don't think Slartibartfast was trying to say anything else. It's just that that rubble will keep moving down.

Please explain how rubble is "worse" than an intact floor. And, if the building can exert force on an intact block, how can it not be exerting force on rubble?

It can exert force on rubble, but not as effectively. With an intact block, all of the weight is resting on the columns. With a huge pile of rubble, more of it is resting on floor surfaces and the like. They are being held up by columns, but the floor may not be strong enough to prevent rubble from crashing through.

Please explain how this would be true and be in accord with Newton's Third Law. This is basic physics.

Because there's at least one more force present besides the impact forces. Gravity. Unfortunately, gravity aids the impact forces on the lower block, increasing the total magnitude of the downward forces on it, while it diminishes the upward force on the upper block.

yes, unless acted on by another force. Did you forget that part?

The lower block is "less able"? to "do anything about it"? According to what physical law? This is getting too stupid to comment to.

In accordance with what I just said above, the lower block must exert a force equal to the force provided by gravity to merely prevent the upper block's downward motion from continuing to accelerate. It must exert a greater force than that to slow it down. And to stop it instantly requires a force several times that of gravity's.

And by the same physical law you seem to love quoting so much, doing so will exert those same forces on the floor being struck. And if it gives way before it's finished stopping the upper block, then it's not going to stop anything.

Merely repeating this doesn't make it true. This is Bazant's "inevitability" argument. It is not true in real life, nor is it true in theory. Moreover, you brush over the fact that both colliding floors are now crushed or severely damaged.

Impact is absorbed both ways. What part of this don't you understand?

We've stated repeatedly that whether the floors are crushed or damaged doesn't matter at all to whether they still have downward momentum.
 
If the floor the pieces hit fails, it's not going to stop anything. Before the "intact rest of the building" can stop the upper block, it has to fall to that floor's surface. And if the topmost floor failed, why would the floor below be better able to withstand a larger mass falling the same distance?

Because energy has been expended in crushing those two floors on both the upper and lower blocks. Maybe another pair of floors would go, and maybe more, but it would not keep continuing, because energy is expended each time, and there is no new energy coming into the system. I.e., there are no new "drops" happening.

Oh no, both floors will likely be reduced to rubble. I don't think Slartibartfast was trying to say anything else. It's just that that rubble will keep moving down.

It is clear he was saying that only the first lower floor would crush. And rubble will not keep "moving down" if it is being held between the supposed upper block and the larger, intact, lower block. It will be stopped.

It can exert force on rubble, but not as effectively. With an intact block, all of the weight is resting on the columns. With a huge pile of rubble, more of it is resting on floor surfaces and the like. They are being held up by columns, but the floor may not be strong enough to prevent rubble from crashing through.

The force it exerts would be greater than that provided by the rubble because it is an intact, integrated structural unit and the rubble is not. If one or two floors fail, this does not mean that the next floors must fail. Fairly quickly the energy gets expended and collapse is arrested.

Because there's at least one more force present besides the impact forces. Gravity.

The impact force is caused by gravity. There is no new force entering here. It's all just one. It is being matched by the upward force of the intact block.

Unfortunately, gravity aids the impact forces on the lower block, increasing the total magnitude of the downward forces on it, while it diminishes the upward force on the upper block.

There's only one alleged impact force: the collapse initiation. The initial impact was matched by the lower block, which transmitted that energy back into the upper block. That's why we see the upper block starting to crush up before crush down could even begin. So not only has that energy been transmitted back but any further energy via gravitation would be matched by the intact unit and/or expended in any possible further crushing of floors.

It's clear this entire argument is based on this childish notion of Supermegagigajoules!! of energy being available, somehow via gravity alone. Bazant's calculations are designed to produce this supernatural abundance of kinetic energy. But it's simply not true in real life.

In accordance with what I just said above, the lower block must exert a force equal to the force provided by gravity to merely prevent the upper block's downward motion from continuing to accelerate.

No. It was already providing the force to stop the upper blocks' acceleration via gravity. For thirty years. It can and would exert a force equal and opposite to the impact force provided by gravity to stop its descent any further past the damaged floors. It's the larger, stronger portion of the building. It overcomes anything the upper block could possibly deliver via gravity.

And by the same physical law you seem to love quoting so much, doing so will exert those same forces on the floor being struck. And if it gives way before it's finished stopping the upper block, then it's not going to stop anything.

Both upper and lower floors are being "struck" in the impact. The force is being transmitted through both upper and lower blocks. Please get this through your collective heads. The lower block is also able to refer the force through a much larger structure than the upper block can, including the ground, if it came to that.

We've stated repeatedly that whether the floors are crushed or damaged doesn't matter at all to whether they still have downward momentum.

Downward momentum is easily and quickly arrested by the taller, stronger, more intact lower block for the reasons I outline above.
 
No. It was already providing the force to stop the upper blocks' acceleration via gravity. For thirty years. It can and would exert a force equal and opposite to the impact force provided by gravity to stop its descent any further past the damaged floors. It's the larger, stronger portion of the building. It overcomes anything the upper block could possibly deliver via gravity.
Your assertion is incorrect. The force required to stop the upper block from continuing to accelerate is similar to the force seen by the lower block for thirty years, but the force required to decelerate the upper block and arrest collapse is greater than the historical force.
 
Downward momentum is easily and quickly arrested by the taller, stronger, more intact lower block for the reasons I outline above.

You still don't understand acceleration and momentum.
 

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