911 physics for dummies

[R.Mackey]

Thanks again. About seeing a physics professor, I'm definetly going to do that one day soon, as I live next door to MIT.

If you aren't currently enrolled at MIT, what I would suggest you do -- as a way to approach the professors in a favorable setting -- is to try to attend colloquia and talks of the different departments, e.g. physics and engineering. Those talks should be scheduled and posted on publicly viewable sites.

A good prof will probably be quite eager to discuss these things with someone genuinely interested in the subject, particularly a prospective student... Much better than cold-calling or just appearing in their offices. They may experience a "new blood" reaction, just like us, since some of them have been e-mail bombarded or even bullhorned by the Truth Movement in the past.

If that fails, try a community college. Much less stress, and generally good quality lecturers. And classes are cheap!

 

[PhantomWolf]

On the other hand, I've seen the claim that the buildings actually fell faster than free fall.

I've seen the claim that the buildings fell faster then freefall because the explosives blew all the air out of the buildings, creating a vacuum that then sucked the buildings down.

 

[PhantomWolf]

Yes, because it would take more energy to move that mass laterally so that it could fall through the air. Think of it as being the path of least energy change.

Thuis is extremely important and one thing that it seems the Truthers just can't understand.

Imagine a sniper shooting at a steel plate. Now it is plainly obvious that a steel has more resistance than air, so the path of least resistance must be around the steel plate right? Why then doesn't the bullet go around the plate? The answer is quite simple, it takes more energy to force the bullet to change its path so that it goes around the plate than it does to deform the point of impact enough to cause a hole and allow the bullet to pass through, and that's what it's about, energy.

The top of the buildings travelled following the path of least energy change, i.e. straight down.

 

[chris lz]

The "path of most resistance" in this case happens to be down

chris lz

So the path of most resistance and least resistance are both down?

Gravy:

Yes, because it would take more energy to move that mass laterally so that it could fall through the air. Think of it as being the path of least energy change.

Still confused. Can someone explain why the path of most resistance isn't "sideways"? I think many people (with very bad physics intuition) would imagine falling sideways to be the path of most resistance, precisely given that it would take more energy. Is the answer that “sideways” isn’t a “path of resistance” to begin with?

Thank you

 

[Minadin]

I think the path of most resistance (energy change) is actually "up".

 

[chris lz]

. . .I suspect therefore that if you put all the papers on the WTC collapses on a physics professor's desk and asked him whether they proved that the collapses were to be expected, the most likely answer would be "Let me get back to you on that."

And once having done a little digging, do you think it likely most would come back to report they reject the truth mvt version of collapse physics?

 

[DannyJ]

After reading this topic, I've found that some people who ask questions are said to be truthers if they get into too much detail in their questions. I'm notreally a truther, more of someone who researches it in my free time and wonders about what hes seeing. So I'll bring something up that seems to kind of get me thinking.

On the North Tower collapse (the Eitenne video on youtube which I'm not allowed to link), if you look at the roof, you see the antenna falls a fraction of a second before the hole building gives way. This indicates the core must of been the first thing to go first (as the core supported the antenna), but the fires I saw from videos didnt seem to be that big (then again, I wasn't in the building, so I don't know the internal damage). Could it have been from the jet fuel that was said to have shot down the elevator shafts that grew bigger and bigger?

 

[Gravy]

After reading this topic, I've found that some people who ask questions are said to be truthers if they get into too much detail in their questions. I'm notreally a truther, more of someone who researches it in my free time and wonders about what hes seeing. So I'll bring something up that seems to kind of get me thinking.

On the North Tower collapse (the Eitenne video on youtube which I'm not allowed to link), if you look at the roof, you see the antenna falls a fraction of a second before the hole building gives way.

Welcome to the forums, Danny. I'm afraid I don't see what you're seeing. It appears to me that the impact zone and the roof are falling simultaneously. Keep in mind that the collapse started by the inward buckling of the wall opposite the side from which this video was shot:

This indicates the core must of been the first thing to go first (as the core supported the antenna), but the fires I saw from videos didnt seem to be that big (then again, I wasn't in the building, so I don't know the internal damage). Could it have been from the jet fuel that was said to have shot down the elevator shafts that grew bigger and bigger?

The fires were in fact that large and severe. For instance, the portion of fire at the far right of this photo, which was taken five minutes before collapse, is larger than the entire NYC apartment building I'm in right now.

As experienced firefighters said,

"We were looking at two large bodies of fires that neither of us in our 33-year careers had ever seen anything that enormous." –FDNY Chief of Safety Albert Turi –Source

"It was the most unbelievable sight I ever saw, up until that point. I had been in some very busy units during my time in the fire department. I broke in, in Engine 46 and Ladder 27 in the South Bronx when the South Bronx was burning down. I was in Rescue 3, which was extremely busy; they covered the Bronx and Harlem. And then as a lieutenant, I was in the Lower East Side when that was burning down. As a captain, I was in Chinatown. I saw some unbelievable fires in Chinatown. What I saw pales in comparison (sic) to anything else I had seen previously." –FDNY Captain Jay Jonas –Source

http://archive.recordonline.com/adayinseptember/jonas.htm

The fires were started by the jet fuel and they spread by consuming the office contents.

 

[Gravy]

would[/i] imagine falling sideways to be the path of most resistance, precisely given that it would take more energy. Is the answer that “sideways” isn’t a “path of resistance” to begin with?

Thank you

Not sure what the issue is here. You seem to be agreeing with us. The path of most resistance would be upward, then sideways, then downward.

These simple diagrams may help you or others better understand why the "toppling" idea doesn't make sense:
A simple graphic explanation of why the top of the south tower didn't fall to the side.

These papers and posts discuss the issue in more detail.

Why didn't the upper part pivot about it's base? See Bazant & Zhou (2001) Appendix II

Eduardo Kausel (MIT): Why the Towers didn't fall like trees

Frank Greening: An analysis of the tipping of the upper section of WTC 2 (PDF)

Physicist Dave Rogers on tipping of tower tops.

Structural engineer "Newton's Bit" on "tipping"

There's much more about the engineering and physics of the collapses at my site, which is linked in my signature.

 

[Apollo20]

DannyJ:

Collapse initiation of the North Tower is very complex and made all the more confusing by the tipping of the upper section. Certain videos mask this effect because the top section is tipping directly away from the camera. This can look like the antenna is dropping into the building (core!) BEFORE the block, (as measured from a point on the roof-line of the facade), starts to move. You need to see collapse videos from other angles to see that the tipping is quite substantial and must be included in an estimation of what falls first. Its a real chicken (antenna) and egg (roof-line) problem, but certainly not evidence of a conspiracy!

 

[Furcifer]

Welcome Chris Iz. I hope your venture into this forum has not completely tainted your views on ALL of its members. Once your make your way past the "Pit of Snakes" and pass the "Trial by Sarcastic Canadian Lawyers" there are some very informed and helpful posters willing assist you in your endevour. In reading this thread I find it interesting that a few (Dave and Ryan in particular) have encouraged you to actually present some of this material to physics profs, teachers etc. in your immediate area, as I have done in the past

The response to your questions by some has been, shall we say, less than encouraging? But you'll be happy to know "typical". You're not being centered out, it seems to be par for the course around here.

As a heads up, pay particular attention to your grammatical style here and be concise in your phrasing at all times. It's much more important here than say Colbert Nation or YouTube. Your usual "neutral" style will get you in trouble.

Good to see you're still at it. PM me anytime if you have any questions. Peace (back to lurking)

 

[chris lz]

Not sure what the issue is here. You seem to be agreeing with us. The path of most resistance would be upward, then sideways, then downward.

Let me put it this way. If the question appeared on a physics exam, worded like this:

In the collapse of a high rise building, what would be the path of most resistance?



would the correct answer be

A up
B sideways
C down
D up, then sideways, then down
E all of the above

So far, the answers I've been given have variously been A, C and D. Can you see why that might be a bit confusing to a physics ignoramus?

Thanks

 

[T.A.M.]

Welcome Chris Iz. I hope your venture into this forum has not completely tainted your views on ALL of its members. Once your make your way past the "Pit of Snakes" and pass the "Trial by Sarcastic Canadian Lawyers" there are some very informed and helpful posters willing assist you in your endevour. In reading this thread I find it interesting that a few (Dave and Ryan in particular) have encouraged you to actually present some of this material to physics profs, teachers etc. in your immediate area, as I have done in the past

The response to your questions by some has been, shall we say, less than encouraging? But you'll be happy to know "typical". You're not being centered out, it seems to be par for the course around here.

As a heads up, pay particular attention to your grammatical style here and be concise in your phrasing at all times. It's much more important here than say Colbert Nation or YouTube. Your usual "neutral" style will get you in trouble.

Good to see you're still at it. PM me anytime if you have any questions. Peace (back to lurking)

Heh, you forgot "Immunization with Kool-Vax".

TAM

 

[T.A.M.]

Let me put it this way. If the question appeared on a physics exam, worded like this:

In the collapse of a high rise building, what would be the path of most resistance?



would the correct answer be

A up
B sideways
C down
D up, then sideways, then down
E all of the above

So far, the answers I've been given have variously been A, C and D. Can you see why that might be a bit confusing to a physics ignoramus?

Thanks

(D) is correct, if the amount of "up" is equal in both (A) and (D) in terms of time, and if the "up" in (A) is immediately followed by down.

TAM

 

[chris lz]

Welcome Chris Iz. I hope your venture into this forum has not completely tainted your views on ALL of its members. Once your make your way past the "Pit of Snakes" and pass the "Trial by Sarcastic Canadian Lawyers" there are some very informed and helpful posters willing assist you in your endevour. In reading this thread I find it interesting that a few (Dave and Ryan in particular) have encouraged you to actually present some of this material to physics profs, teachers etc. in your immediate area, as I have done in the past

The response to your questions by some has been, shall we say, less than encouraging? But you'll be happy to know "typical". You're not being centered out, it seems to be par for the course around here.

As a heads up, pay particular attention to your grammatical style here and be concise in your phrasing at all times. It's much more important here than say Colbert Nation or YouTube. Your usual "neutral" style will get you in trouble.

Good to see you're still at it. PM me anytime if you have any questions. Peace (back to lurking)

Thank you 3body. I'll keep that in mind. It took me a few days to figure out the forum's "initiation rites," and where everyone's coming from. I'm sure I overreacted, and I certainly didn't mean to paint everyone with one brush based on a few posts.

 

[chris lz]

(D) is correct, if the amount of "up" is equal in both (A) and (D) in terms of time, and if the "up" in (A) is immediately followed by down.

TAM

Looks like I better enroll in a physics course before I ask any more seemingly simple questions.

 

[Anti-sophist]

Let me put it this way. If the question appeared on a physics exam, worded like this:

In the collapse of a high rise building, what would be the path of most resistance?

would the correct answer be

A up
B sideways
C down
D up, then sideways, then down
E all of the above

So far, the answers I've been given have variously been A, C and D. Can you see why that might be a bit confusing to a physics ignoramus?

Thanks

The reason you are getting different answers.. and the reason the question seems confusing is because it's fundamentally ill-formed.

The term resistance has a precise meaning, scientifically, and for the purposes of our discussion its completely irrelevant. For this situation, there's no good definition of "resistance" or how one would quantify the "resistance" of the "path" that a collapsing building took. And given any reasonable definition of "resistance" there's no such way to quantify what it would be for an entire building.

The notion that objects move in the path of "least" resistance is an emergent property of systems. There are no physical laws that talk about objects traveling the path of least resistance (unless we include the behavior of an electron, and even then it's not technically true).

Now, without getting super pedantic and tossing your question in the garbage and leaving it at that, the "most" correct answer, in my view, is A. But to be certain, we'd need to define what "resistance" means...

During the actual collapse of a building, some objects will fly up, and then later sideways and down. Some will go almost straight down. Some will go sideways, then down. Each of these objects is traveling their own path of least resistance (given some reasonable definition)... and so how do I take a multitude of objects traveling different paths and somehow characterize that as a single path for the entire structure? "Average" them? That answer is gonna be alot closer to straight down than straight up.

One thing I know for certain.. is that under no circumstances can straight down be considered the path of "most" resistance, given any reasonable definition of resistance.

 

[Gravy]

Let me put it this way. If the question appeared on a physics exam, worded like this:

In the collapse of a high rise building, what would be the path of most resistance?

As written, that question would not appear on a physics exam! For one thing, there are many different types of high rise construction and many different ways that a building can fail and fall.

Don't make this (or allow us to make it) more complicated than it is. In the case of the Twin Towers, the floors and their connections in the bottom part were not strong enough to support the falling mass of the top part. Therefore the collapses continued to the ground.

Keep in mind that buildings and gravity don't only interact when something goes wrong. All buildings are constantly fighting like hell to not be flattened by gravity.

 

[chris lz]

Now, without getting super pedantic and tossing your question in the garbage and leaving it at that, the "most" correct answer, in my view, is A. But to be certain, we'd need to define what "resistance" means...

Thanks for your reply Anti. That is precisely the kind of detailed but also comprehensible answer I hoped for when coming here.

One thing I know for certain.. is that under no circumstances can straight down be considered the path of "most" resistance, given any reasonable definition of resistance.

versus

The "path of most resistance" in this case happens to be down

So in what sense then, if any, is the latter statement correct?

 

[chris lz]

As written, that question would not appear on a physics exam! For one thing, there are many different types of high rise construction and many different ways that a building can fail and fall.

Don't make this (or allow us to make it) more complicated than it is. In the case of the Twin Towers, the floors and their connections in the bottom part were not strong enough to support the falling mass of the top part. Therefore the collapses continued to the ground.

Thanks for your input, and for the earlier links. I'll try to read them when I have time.

The reason I bring this up is not because I doubt for a moment the buildings would have fallen all the way down. It's because I run into the stock truther phrase "the buildings fell in the path of most resistance" so often, and I wanted to have a nice rebuttal available.

Given what has been said above, may I tell said truthers I've never met a debunker who thinks the towers should have fallen up? That would make my day.