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4th July 2011, 07:16 AM | #121 |
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Yes you may. But no, I'm not missing anything, just simplifying the problem. There are no additions. The spec is 58 kN, meaning that is the max that can be attributed to the plane by the pole. By Newton's 3rd Law, that is also the max that is transferred to the pole by the plane. Because of this, the energy required to send the pole 'flying' is used up in the fracturing and deformations. No energy left to 'fly'. So no, by the spec definition, I am missing nothing.
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4th July 2011, 07:16 AM | #122 |
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4th July 2011, 07:24 AM | #123 |
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4th July 2011, 07:33 AM | #124 |
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I am confused...
My 54N is the force needed to accelerate the 150kg of pole mass to 154m/s over a distance of - what was my assumption? 20m? - while assuming that no additional force is needed to bend the pole. But we do need force to bend... On the other hand, my math was describing an inelastic collision, meaning that deformation work is implied without additional assumptions... I just don't know how that work gets distributed between the plane and the pole. Hmm. Gotta think about that in my hammock - the sun's coming out as I type |
4th July 2011, 07:34 AM | #125 |
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It falls over. I think Beachnut posted some photographs that illustrate this earlier in the thread. Keep in mind that Oystein's "sum" was oriented to a two-body solution for simplification. The forward velocity is a vector which is converted to rotational velocity as the pole falls.
Now we could make this a much more complex solution by doing those conversions of the velocity vector, but the spec simplifies it for us. Maximum force exerted on the plane cannot exceed 58 kN by spec. That is a sum of the forces involved, and by Newton's 3rd Law, that is equal to the force transmitted to the pole by the plane. So the pole is going nowhere. By design it is going to fall over because the forces applied to the pole are 'absorbed' by the fracturing and deformations. |
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4th July 2011, 07:43 AM | #126 |
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Fall over, in the real world, of course. I modelled the worse case, which involves fly-off.
In reality, the collsion is neither totally inelastic (one of my base assumptions) nor right on the pole's center of gravity. This means the pole gets partially kicked away in an elastic collision, picks up rotational momentum, too, and gets out of harm's way faster than I assumed. The result will be that it picks up less speed, less momentum, less kinetic energy from the plane. This in turn means that the plane decelerates even less. It could however mean that there is momentarily a peak of higher impact force than those 54/58kN. Which doesn't matter that much. The higher the peak, the shorter its duration; what matters is how much of kinetic energy is transformed into deformation of materials. My calculation offered an upper bound: 1.78MJ. That is the kinetic energy of a VW Golf travelling at 180km/h / 110mph. However, since collision was less perfect, less damaging than my worst case assumptions, damage was also less than a Golf speeding into concrete. |
4th July 2011, 07:44 AM | #127 |
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We don't have to make it more complex, we can make it more simple and use a common sense analogy to prove that Oystein is right and BCR is wrong.
Take a broomstick and stick it into a lawn only so far that it barely stands up. Then take a baseball bat and hit it with full force somewhere in the top region. Unhand the bat. Will the broomstick fall over? Of course not. It'll go fly together with the baseball bat. |
4th July 2011, 07:45 AM | #128 |
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Don't try to think too hard about it, because from here we can go a long way from simple. Keep in mind that you also have gravity acting on the pole, bending, fracturing, etc. The actual vector(s) involved are 3d, not linear as we've assumed for the purposes of simplification. The plane's wing is not straight edge, but angular. Some poles bent and most likely were 'drug' along with the plane a short distance, so some forward velocity can be expected as well. However, the egg-head traffic engineers have done all that work for us and designed the pole to meet a specific specification and that is to limit the forces on the plane to 58 kN. That makes our job easier, since that sets the upper force limit for the encounter.
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4th July 2011, 07:48 AM | #129 |
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That's because we will neither break the broomstick nor the bat: What you have there is a completely elastic collision, during which the lighter collision partner picks up much more speed than the heavier one loses.
The collision of pole and plane went into mostly inelastic immediately - we are talking indeed about forces and energies that your little experiment hasn't scaled to properly. |
4th July 2011, 07:50 AM | #130 |
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No ma'am, the broomstick is not attached to the earth. A certain amount of force is required to separate the broomstick from the earth. Until that threshold is breached the broomstick goes nowhere, but your arm will sure tingle from the force transferred back through the baseball bat.
These poles are designed to fall over CE. You don't have to take my word for it, you can just read the specs and look at the thousands of photographs of such encounters already posted on the internet. |
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4th July 2011, 07:58 AM | #131 |
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4th July 2011, 08:00 AM | #132 |
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Exactly. But if I hit hard enough, the stick will be hit by a force much greater than is necessary to release it from the earth and will go flying. Same with the pole. The specification you cited is designed to reduce the force potentially damaging the plane, as discussed earlier. It's like my "only so far that it barely stands up" analogy which is designed to not make my poor arm hurt when I hit the stick. |
4th July 2011, 08:09 AM | #133 |
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Yes, unless it has a 'connection' with the earth designed to fail and absorb the impact energy (which a broomstick stuck in the ground does not have).
Quote:
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4th July 2011, 08:15 AM | #134 |
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4th July 2011, 08:18 AM | #135 |
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4th July 2011, 08:25 AM | #136 |
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Yeah, first they admit they don't know anything about physics, then they reach a conclusion on a physics discussion using principles they don't understand. Now, if the plane hit one of those wooden light poles her analogy would be a good one, except the wooden post would most likely crack in two before flying off anywhere. In this case, we are dealing with a pole with specific limitations and design features.
1) Limit force to the plane to 58 kN. 2) Deform, buckle, fall away as not to be a further obstruction to the plane. A whole different animal than a broomstick Side note: Oystein is not wrong (except in his 'additive' conclusion). He is simply using a standard inelastic collision model w/o consideration to the design specifications (unknown to him at the time of his exercise). It is a valid model as far as it goes. Will it attain some forward velocity? Depends on how it was hit and a lot of independent variables we really can't predict. Most likely, yes. However, in general, the pole falls over. If you examine the photos of the poles at the Pentagon, one fell right at the base (straight over), one fell at the base but to the side, while another went forward a few meters. |
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4th July 2011, 08:39 AM | #137 |
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Again, the calculations from my calculations are NOT correct, insofar as the assumtions are geared towards maximum destruction, assuming things that evidenctly did NOT happen in real life. My calculations come up with an upper bound for destructive energy, momentum transfer and deceleration. Reality saw significantly lower numbers!
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4th July 2011, 08:47 AM | #138 |
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I just experimented on my rooftop terrace. The materials involved:
- A bamboo stick, about 1m tall - A concrete brick - A concrete flooring I made the bamboo stick stand upright for long enough to hit it with the concrete brick which I swung by hand. Sorry, I have no baseball bat. I hit the stick near the top. Observations: - The stick picked up both forward and rotational momentum - It hit the ground not far (twice it's own length) from its base and jumped a little forth from there - Where it hit the ground depended much on whether I swung the brick level, or with a bit of downward or upward velocity. As the 757 was descending as it hit the poles, and hit them high, I'd expect them to slam into the ground very close to their bases. There, they would not quite bounce and slide off like a bamboo stick does on concrete flooring. The inelasticity of the pole vs. the elasticity of the bamboo would make the pole stop much sooner, relatively. Conclusion: Pole would not "fly off" but fall down and slam into ground. ETA: With bamboo stick attached to ground, I'd expect even more rotational vs. longitudinal momentum, ergo a slam into the ground even closer to the base. |
4th July 2011, 08:49 AM | #139 |
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Your analogy isn't particularly correct. The force applied near the top of the pole is countered by a force applied in the opposite direction at the bottom of the pole up until the time the bottom breaks free (at 58kN). Those two forces, separated by a distance, form a moment which tends to rotate the pole. By the time the pole breaks free, it is rotating down away from the plane and falls to the ground. Face it, the poles were DESIGNED to do what they did, and they performed as expected.
Oystein, your calculation for the pole doesn't say that it either was or wasn't connected. You assume a 13 m "contact distance" with the plane based on the rotation of the pole about the bottom, which it does by being connected. Your numbers were light, because were it only 54kN, the poles would (perhaps) not have broken free. However, decreasing the assumed contact distance would increase the force. Ergo, BOTH you and BCR are right. Ultimately, it is clear that there was nothing suspicious about the poles and their failure to stop a screaming jetliner. |
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4th July 2011, 08:56 AM | #140 |
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4th July 2011, 08:58 AM | #141 | |||
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I think what happened here is that Oystein didn't know where the poles were found and innocently did his calculations, while BCR knows and maybe told Oystein by now that there must be something wrong with his calculation, because "reality" shows something different. Namely that they "fell over". One even hit a moving cab without hurting the hood, the backseats or the driver.
Here's the "evidence" (it skips to 30 seconds in and lasts around a minute) of what happened and where the poles were found:
This semi-official presentation is designed to make a "counter intuitive outcome" plausible, as the disclaimer says. Plausible deniability is the term, I guess. Oystein, I see your latest post in the preview. Don't forget that this happened on a bridge "above" the Pentagon. And as you can see in the video, nothing "slammed into the ground", they simply "fell over". |
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4th July 2011, 09:01 AM | #142 |
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And what does this "evidence" suggest to YOU, CE?
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4th July 2011, 09:04 AM | #143 |
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In the general spirit of nitpicking, what exactly does the 58kN breaking point of the poles refer to? Does it mean the base will snap if a sideways force of 58kN is applied to the post at vehicle bumper height? If so then there's an enormous mechanical advantage gained by the wing if it struck the pole, say, three quarters of the way up, rather than 2 or 3 feet off the ground.
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4th July 2011, 09:05 AM | #144 |
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This is entirely incorrect. Your assumptions result from your personal bias, not from inference and reason.
I knew at least since the photo analysis thread some 3 months ago whereabouts the lamp posts came to rest - close to their bases. My calculations - I am repeating myself - did not aim to model the real world, but to come up with an easy enough calculation that gives us an upper bound on the forces, accelerations, speed losses, and energy converted. My model assumptions - I am repeating myself - were not taken from real life, but geared towards maximum destruction, assuming a fully inelastic head-on (no angular momentum) collision with the entire pole, giving it the same speed as the plane had. It was clear to any intelligent person with a sufficient background in high school ("Oberstufen-") physics, from the beginning of my calculations to the end that I never ever pretended to predict movement and other behaviour of the poles. Look at that grinning smiley in the mirror, CE. laugh at yourself, because you just don't understand. |
4th July 2011, 09:09 AM | #145 |
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4th July 2011, 09:12 AM | #146 |
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Assumptions, Oystein? Oberstufenhumor, eh? You didn't know that they were found close to the base, as is obvious by the hilighted parts of your calculation, especially this one:
Originally Posted by Oystein
You assumed that they were found somewhere on the lawn, after a chaotic journey maybe even including having "bounced off" the Pentagon, as you said. Why are you so dishonest, Oystein? |
4th July 2011, 09:14 AM | #147 |
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As I wasted my time trying to explain to CE, we are dealing with a force vector that has 3 components to it. In this case, your experiment only served to verify what CE was unable to grasp. In beachnut's photo's in the earlier post illustrated, the car hit below the center of gravity setting up a rotational vector. In our case, the plane hits above the cog with an opposite rotational vector. Of course we would not want to confuse CE with vector components or anything like that.
All of this right and wrong stuff is not appropriate for this discussion. We are dealing with models based on sound physics principles to help visualize a real world phenomenon. We each (if we know anything about engineering) understand that there are boundary conditions for those models. Oystein was absolutely correct in his approach using momentum and an inelastic collision. Since he did his model, we now know of a design constraint inherent with the poles. His results are not "correct" only in the sense that it is a model, not a reconstruction of the actual phenomenon, however his results are on the same order of magnitude as the design constraint. He used the correct approach to the problem as opposed to the M = FA nonsense being bantered by the YT guy. |
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4th July 2011, 09:26 AM | #148 |
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Incorrect.
You are interpreting my words incorrectly: I most certainly did not mean they bounced off the Pentagon. What a moronic idea! Bounced of the wing (as opposed to stuck together with the wing, as happens in an ideal inelastic collision). This to show that the real world collision was unlike my model assumption of perfect inelastic collision, which was geared towards maximum desctruction. ETA: Some poles WERE found on lawn. As the video you posted clearly shows. Why are you so dishonest, CE? -> <- (I can grin at you, too) |
4th July 2011, 09:35 AM | #149 |
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It means by design, whether by use of deformation or a 'break-away' feature, the pole will not exert more than 58 kN to the aircraft regardless of impact point. It would be impossible to predict what point an impact might occur, so the spec applies to all impact scenarios. So impact at one point could mean only 20 kN was delivered to the aircraft, or 45 kN at another point of impact. The spec requires only that it is less than 58 kN in any scenario.
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4th July 2011, 09:42 AM | #150 |
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In fact that's all you have. You also said this:
Originally Posted by Oystein
so you were obviously assuming that the poles behaved in the "intuitive way" like in my broomstick analogy. You are barely fooling yourself. Anyway, I made my argument, have fun at youtube. I'll follow the sun. |
4th July 2011, 10:00 AM | #151 |
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4th July 2011, 10:17 AM | #152 |
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Incorrect again.
You totally fail to understand and appreciate model assumptions. One last try to teach you a little: Inelastic collsion means that the two colliding bodies (in this case: The plane and the lamp post) stick together. The faster of the two becomes slower, and the slower becomes faster, as they now travel on jointly at the same speed. This involves the acceleration of the slower partner (the pole) and deceleration of the faster partner (the plane). Acceleration cannot happen instantly. Instantly meaning delta-t = 0 seconds, for that would mean that an infinite force would have to be applied. Infinite forces do not exist in this universe. So we need to estimate the time that it takes for the entire pole (150kg mass) to pick up the speed of the plane - remember: I am assuming a perfectly inelastic collision with the entire mass of the pole, an assumption that I am quick to point is neither realistic nor was reality. It is just the assumption that would allow the post to do the greatest damage to the wing - remember how I told you several times now that my assumptions are not meant to model reality, but are a worst-case scenario geared towards maximum destruction? Fine. Now, in my model, I did assume that the pole would rotate around its base, and would thus stay in contact with the plane as long as it has not rotated out of the path of the wing. I didn't explicitly state it, but there was a little theorem of Pythagoras involved when I figured out that 13 meters distance of contact might be a reasonable estimate. Note that my assumptions are now not consistent anymore - I first assumed central collision (no angular momentum), now I say the pole rotates. Is this a problem? No, because I never meant to model the real movement of the pole, I am still (remember?) on a track to estimate an upper bound to the forces at hand. So I may be excused for totally ignoring angular momentum and assuming that only longitudinal momentum is gained by the pole. The point of the 13m being that, given the geometry of the pole, the distance during which momentum transfer takes place could not be any larger. At the end of my model collosion, the pole sticks to the wing by its top end and flies off into the sunset with the speed of the plane - maximum momentum transfer has taken place. For this scenario, which involves the maximum energy lost to deformation (= damage to plane and pole), I calculate the delta-v and delta-E. All this to show how wrong (by a factor of at least 500) the YT-guy is. And that was the purpose of my calculation. Now let us remember - again! - that my assumption of total inelastic momentum transfer to the entire pole is an unrealistic assumptions geared toward maximum damage. Let's remember - again! - that in the real world, the collision had an elastic component that would make the pole bounce off the plane somewhat, and that it does pick up angular momentum, and breaks at 58kN max, thereby reducing the contact surface, we will quickly see that my calculation greatly over-estimates the momentum transfer, the delta-v, and the damage. Quite independent from the model I developed, I performed your little broomstick-experiment to find that indeed the pole would rotate into the ground pretty near its base instead of joining up with the plane. Thus, in reality, the collision is brief, limited in force, limited in momentum transferred, destruction is much less than what my numbers estimated as upper bound, and the pole will fall over and slam into the ground very near its base. |
4th July 2011, 11:03 AM | #153 |
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You can't teach those who do not wish to learn.
CE shows, in a nutshell, how a truther's own prejudice precludes them from understanding. If the physics doesn't match the "inside jobby job" then just discard the physics, make some facile comment and leave, arms raised in faux triumph. |
4th July 2011, 11:08 AM | #154 |
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At least I learned a little: How it is possible that CE, who I consider to be quite intelligent, can buy the crap sold by CIT: He simply doesn't enough physics to see why their flight path with flyover is impossible.
The basic reasoning: I don't understand why horses can't fly, so I may believe they can. |
4th July 2011, 11:17 AM | #155 |
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Pretty much. CE sees a light-hearted dispute between two debunkers who have a clue about physics and seizes upon an apparent disagreement as CT fuel.
For what it's worth, we've been waiting for a year or three for CE to reconcile the supposed North of Citgo flightpath with the total lack of >70° bank angle. We will continue to wait. Until the cows come home, no doubt. CE, like a majority of Truthers, is agenda-driven rather than fact-driven. Fact schmacht. |
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4th July 2011, 11:38 AM | #156 |
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Actually, there was no dispute between Oystein and me. If you read back, the entire dispute was generated by CE. Beyond that, I am a truther, Oystein is a de-bunker if such classifications are warranted.
CE just grabbed onto something Oystein said in his modeling which to him somehow contradicted what I said. In reality, it did not. I've resisted bringing impulse (force * time) into the discussion again for fear of muddying the waters (it is however, alluded to in the spec). As I have said over-and-over again, Oystein's model is a valid one for general force estimation in a simplified way. To go nitpicking over complex deviations of the model from real-world is unfair and unwarranted. So all of the 'dispute' is generated by CE. Oystein and I are simply working the problem and reasoning our way through it together. |
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4th July 2011, 11:39 AM | #157 |
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You may have missed it, but I addressed that angle nonsense with the originator, Reheat, some time ago after you brought it up. It's junk science. The poles would maybe gently "fall over" if the event would have happened in super slowmo like in that hilarious presentation, but not under real circumstances where under the immense impulse the weakest point at the base immediately fails (as designed) and the (however elastically bend) pole sails off chaotically. What we see in the video is the opposite of Oystein's model, and much more detached from the real circumstances. |
4th July 2011, 11:39 AM | #158 |
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It is hard for people who can't grasp physics to understand reality, the poles fell down, and you presented proof of how they fell down with photos and a model, yet you call your debunking of the CIT dolts, "counter intuitive", when it is logical based on physics which CIT don't use to sell their lies on DVD. Can you imagine CIT using physics? It would be close to the 11.2g moron math of Balsamo. CIT are idiots when it comes to investigation, their videos are proof.
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4th July 2011, 11:51 AM | #159 |
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They don't fall over gently. They fall over quite violently.
They will likely bend at the base when design forces are exceeded, cause that's how they are designed, but not necessarily separate from the ground quite so easily. Pretty much like the poles at slalom skiing. And please STOP MISREPRESENTING MY MODEL as even attempting to duplicate real world movements, as I have told you several times now that this is outside the scope of my model! Why do you so stubbornly insist on being so dishonest?! Everybody is looking and seeing how you keep on being dishonest! Stop it already" |
4th July 2011, 11:59 AM | #160 |
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