With extremities I wanted to say the amount of kinetic energy that is lost in the collision. Of course momentum is conserved as I said. And most practical collisions are inelastic, Greening's assumption is correct if you assume a real 100% perfect pancaking. Even this is not the more modern progressive collapse assumed.
Peanut gallery: The WTC 1,2,7 collapsed from impact damage and fires
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With extremities I wanted to say the amount of kinetic energy that is lost in the collision. Of course momentum is conserved as I said. And most practical collisions are inelastic, Greening's assumption is correct if you assume a real 100% perfect pancaking. Even this is not the more modern progressive collapse assumed.
Hellbound
Merchant of Doom
einsteen:
You re confused, wrong, and showing yuour ignorance.
GReenings assumption, re: inelastic/elastic collision, is 100%, unequivocally, absolutely correct. Period. No ifs, ands, or buts. DOesn't matter what scenario or situation. The collision is inelastic, period. In fact, NO real-world collision is elastic, ever. An elastic collision is a mathematical simplicity.
You are confusing this issue with something entirely different. I suspect your intention is to say that some of the energy and momentum was "bleed off" into the debris being thrown, rather than hitting the lower floors. This has NOTHING to do with whether the collision is elastic or inelastic, and continuing to chant the elastic/inelastic mantra simply shows how little you actually know about the relevent physics and how little research you've actually attempted to do before spouting nosense.
I refuse to spoon-feed anyone knowledge who could just as easily find it themselves with a minimal of work. But I will be here, consistently, to show that those most vocal against the "official theory" of 9/11 are often those most ignorant of the science and the facts involved, you yourself being a perfect example.
Now, if you expect your arguments to be nderstood or taken seriously at all, I'd suggest, at a minimum, understanding the terminology one is using instead of throwing around big words in an attempt to appear educated.
You re confused, wrong, and showing yuour ignorance.
GReenings assumption, re: inelastic/elastic collision, is 100%, unequivocally, absolutely correct. Period. No ifs, ands, or buts. DOesn't matter what scenario or situation. The collision is inelastic, period. In fact, NO real-world collision is elastic, ever. An elastic collision is a mathematical simplicity.
You are confusing this issue with something entirely different. I suspect your intention is to say that some of the energy and momentum was "bleed off" into the debris being thrown, rather than hitting the lower floors. This has NOTHING to do with whether the collision is elastic or inelastic, and continuing to chant the elastic/inelastic mantra simply shows how little you actually know about the relevent physics and how little research you've actually attempted to do before spouting nosense.
I refuse to spoon-feed anyone knowledge who could just as easily find it themselves with a minimal of work. But I will be here, consistently, to show that those most vocal against the "official theory" of 9/11 are often those most ignorant of the science and the facts involved, you yourself being a perfect example.
Now, if you expect your arguments to be nderstood or taken seriously at all, I'd suggest, at a minimum, understanding the terminology one is using instead of throwing around big words in an attempt to appear educated.
The scattering and dust hanging in the air is something to add to it, there are so much factors involved, is say at least that it is not so trivial as in Greening's paper. And I was at least able to calculate Greening's speed value without excel sheets although he doesn't mention it explicitly, nothing special even you can do that, what is your education btw mr Big Mouth
Stop with the insults, einsteen. It does not help your case.
I've already explained to you that the collapse speed is not a strong function of mass lost over the side. All that needs to happen is that each floor impact needs to be strong enough to break the floor below. After that, it doesn't matter if the impact is twice what the next floor can handle or ten times, it will still collapse, and the rate of collapse will still accelerate.
Hellbound
Merchant of Doom
My education is high school degree with some college physics.
Enough to know that what you're talking about...things being ejected fromt eh collapse zone, has NOTHING to do with wether it's an elastic or inelastic collision. I also know enough to understand that "semi-elastic" is a meaningless term, and that you don't understand the terms well enough to be able to use them correctly.
If no kinetic energy is lost it is elastic, if it is perfectly inelastic (as Greening assumes) the maximum amount of kinetic energy is lost, not 100% of course, but the maximum that can be lost.
Insults ? I was attacked, I have the right to defend like an American
Insults ? I was attacked, I have the right to defend like an American
Hellbound
Merchant of Doom
TO be fair, I started that.
And as soon as any evidence can be presented to show my characterizations of ignorance, using terms he doesn't understand, and a poor grasp of the physics involed are incorrect, I will be the first to apologize.
I'm just rather tired of people who, apparently, slept through high-school physics (or didn't take it at all) latch onto some physics word they don't understand then toss it about everywhere as if it proved something.
It reminds me of my fourteen month old daughter getting a new toy that plays music, and walking around the house playing it constantly for several days ina ro as if it's the greatest thing. Although in my daughter's case I can understand the behavior.
umm...i dunno about spoon feed, I have a Diploma in Electrical Engineering Tech, I have honors in College Physics (Intro), but I did all that 12 years ago, and then went into medicine, so while I dont need spoon feeding, my brain hurts when I have to fire up the old physics engine again...so I dont mind a little quasi-spoonfeeding of it. I promise those who do, I will break down any medical condition for you if you ask...lol
TAM - EET, BSc (Med Sc) MD, CCFP
Hellbound
Merchant of Doom
If no kinetic energy is lost it is elastic, if it is perfectly inelastic (as Greening assumes) the maximum amount of kinetic energy is lost, not 100% of course, but the maximum that can be lost.
Insults ? I was attacked, I have the right to defend like an American
Yes, you do. So when are you going to start doing anything that actually rebuts my statements?
Again, with this post, you have confirmed that you do NOT understand the principles involved, you don't know what ineleastic or elastic actually mean in application, you are woefully ignorant of the physics, you are too lazy or too ignorant to do the minimal anmount of research it would take to understand your lack, yet you presume to point out the flaws of peopel who actually recieved an education in the subject?
Astounding arrogance.
I'm happily awaiting your defense of yourself.
It isn't about having the right, it's about choosing whether to be constructive or disruptive.If no kinetic energy is lost it is elastic, if it is perfectly inelastic (as Greening assumes) the maximum amount of kinetic energy is lost, not 100% of course, but the maximum that can be lost.
Insults ? I was attacked, I have the right to defend like an American
There is no such thing as "perfectly inelastic," and your comment about "maximum kinetic energy being lost" is nonsensical. Energy and momentum are always conserved, always. However, energy has many different forms it can take. Momentum does not. This is why you are confused.
Greening's assumption about the inelastic floor collision, again, is absolutely correct.
Hellbound
Merchant of Doom
TAM: point taken.
Okay, a bit of spoon feeding then.
Elastic and inelastic collisions do have to do with whether kinetic energy is conserved or not.
ALL real-world collisions will be inelastic. Even billard balls (although they are the closest to elastic we know of).
Where einsteen is confused is what this actually means.
An inleastic collision does NOT mean the energy just goes away. Energy is ALWAYS conserved. Period.
An elastic collsion means ALL of the kinetic energy remains kinetic energy...none if it is used to break anything, to deform anything, to create heat, or to bend anything. The collapse could only be elastic if the entire building fell as one piece with nothing breaking.
Treating it as ineleastic is absolutely correct. In an inelastic collision, Kinteic energy is not conserved. IN fact, by the end of the collapse, 100% of the kinetic energy should be gone (or else there's still something moving somewhere). However, the TOTAL energy is conserved. The kinetic energy is converted into mechanical energy (deforming and breaking the componenets), heat energy (from friction and impact), and other kinetic energy (imparted, for example, to the debris being flung outward).
Essentially, the total energy available for the entire process is equal to the gravitational potential energy of the building. As it falls, that GPE is converted to kinetic energy (KE). As parts of the building begin to impact, that KE is converted into other types of energy (mechanical deformation, heat, etc) or redirected into kinetic energy in a different direction.
And, as R. Mackey stated above, you only need enough energy to collapse a single floor. IF you agree that the top ten floors falling could collapse the floor underneath it, then 90% of the building mass could be ejected and there's still more than enough energy left to do the damage.
IF you actuall look at the fall time against free fall time, about 20% of the total energy involved in the collapse is unaccounted for. That percent of the total GPE of the building is more than enough to do the damage and throw the debris. And that 20% figure does not consider the fact that the building didn't fall all the way to ground level...you could add as much a 10% more to it when that is taken into account.
Okay, a bit of spoon feeding then.
Elastic and inelastic collisions do have to do with whether kinetic energy is conserved or not.
ALL real-world collisions will be inelastic. Even billard balls (although they are the closest to elastic we know of).
Where einsteen is confused is what this actually means.
An inleastic collision does NOT mean the energy just goes away. Energy is ALWAYS conserved. Period.
An elastic collsion means ALL of the kinetic energy remains kinetic energy...none if it is used to break anything, to deform anything, to create heat, or to bend anything. The collapse could only be elastic if the entire building fell as one piece with nothing breaking.
Treating it as ineleastic is absolutely correct. In an inelastic collision, Kinteic energy is not conserved. IN fact, by the end of the collapse, 100% of the kinetic energy should be gone (or else there's still something moving somewhere). However, the TOTAL energy is conserved. The kinetic energy is converted into mechanical energy (deforming and breaking the componenets), heat energy (from friction and impact), and other kinetic energy (imparted, for example, to the debris being flung outward).
Essentially, the total energy available for the entire process is equal to the gravitational potential energy of the building. As it falls, that GPE is converted to kinetic energy (KE). As parts of the building begin to impact, that KE is converted into other types of energy (mechanical deformation, heat, etc) or redirected into kinetic energy in a different direction.
And, as R. Mackey stated above, you only need enough energy to collapse a single floor. IF you agree that the top ten floors falling could collapse the floor underneath it, then 90% of the building mass could be ejected and there's still more than enough energy left to do the damage.
IF you actuall look at the fall time against free fall time, about 20% of the total energy involved in the collapse is unaccounted for. That percent of the total GPE of the building is more than enough to do the damage and throw the debris. And that 20% figure does not consider the fact that the building didn't fall all the way to ground level...you could add as much a 10% more to it when that is taken into account.
No Mr.Mackey, I'm not confused,"perfectly inelastic collision" is a term often used. I know the laws of conservation of momentum and energy.
rwguinn
Penultimate Amazing
Another pair of obviously incorrect statements...
Yes, you are confused. This quote of yours:
...makes no sense at all. Kinetic energy is not "lost." If, as you claim, you understand the Laws of Conservation of Momentum and Energy, you undertand this, but apparently you do not.
I have a Physics degree, and I have never heard the term "perfectly inelastic collision" before. It's just "inelastic." There are no qualifiers applied, ever.
Kinetic energy can be transformed (as you said in your other post), in the case that the maximum amount of kinetic energy is lost it is lost due to deformations, heat or whatever. If a mass collides onto an other mass (say the 2nd is standing still), how would it collide to lose as much kinetic energy as possible ? In fact merging together with a new collective speed that is lower than the initial speed. I've also a physics degree, although it's awhile ago.
Look, there is no "maximum." There are NOT differing degrees of inelasticity in a collision. The masses do not "decide" how to convert as much kinetic energy as possible.
In that case, I am completely baffled as to your complaint.
Why don't you start from scratch? What do you find suspicious in Greening's paper? Please try to use precise language this time, the kind they used in your physics classes.
It's about 10 years ago already (s*h*i*t I'm old), forgive me if I have to refresh my memory sometimes, as far as I remember it's no matter of a ball or block deciding what he or she wants to lose but pure the properties of the material.
Greening...First of all where we already had big discussions about, ok I just made this
I don't think this is what we see.
Greening...First of all where we already had big discussions about, ok I just made this
I don't think this is what we see.
I don't either. The falling block will also experience deformation.
That deformation, however, does not affect its momentum. Its mass remains the same, as does its net velocity.
So, what -- in detail -- do you think is wrong? What do you think we do see?