tsig
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How can you possibly know that? Are you denying there was structural damage or that heat can weaken steel?
The physics toolkit
- Thread starter jaydeehess
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- david chandler
How can you possibly know that? Are you denying there was structural damage or that heat can weaken steel?
And I cannot fathom that you could be this incompetent.
But it does explain why you ended up as a truther.
My analogy is precisely on the mark. It needs no adjustment from you.
You stated:
Tony Szamboti said:
This is simply, ludicrously wrong.
CoM ALWAYS holds for two colliding bodies. Zero exceptions in this universe. And CoM has NO qualifier that says "... as long as the impacted body is strong enough to support the impacting body".
End of story.
In energy terms, the impacting body must do work BOTH to break bonds AND to accelerate the impacted body. Even if you decrease the strength of the bonds (thereby reducing the amount of work done to break them), you STILL must accelerate the mass. Accelerating a mass requires that you apply a force over some distance, requiring that you do work. Doing work requires an input of energy.
Ergo, hitting a layer of ice (requiring you to break strong bond & accelerate the mass of ice) will take more work (i.e., energy) out of the falling body than hitting water (with its weaker bond but equivalent mass). But hitting the "weaker" water STILL requires that you accelerate the water. It is totally irrelevant that the water "is not strong enough to support" the steel block.
And accelerating the water decelerates the steel block. Exactly in conformance with the law of CoM.
Your statement that "there is no deceleration until the object hits something which is more than strong enough to support it" is ludicrous.
BTW, why don't you get your terminology up to an 11th grade level of competence.
A decrease in velocity over some interval of time is not a velocity. It is a (negative) acceleration. Aka, a deceleration.
A decrease in acceleration over some interval of time is not a deceleration. It is a jerk.
Every time you refer to a decrease in acceleration over some time interval as "a deceleration", it demonstrates how woefully confused (and/or sloppy) you are about trivial engineering matters.
Perversely argumentative and incompetent.
No way to go thru an engineering career, Tony.
Tom
PS. Since you stand as a singular bastion of stupid on this issue, with everyone who understands remedial physics or mechanics telling you that you're totally wrong, and you simply asserting - time after tedious time - that everyone else is wrong & you alone are right ...
... why don't you suggest a professor of physics or mechanical engineering. Someone that YOU would accept as an expert and be willing to come here and provide an independent judgment. Then we'll attempt to get him here and weigh in.
Let's see if you have the as-yet-undemonstrated ability to learn anything from anyone. Even your own expert.
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Tony Szamboti
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I never referred to a reduction in acceleration as a deceleration. In fact, I have had to explain the difference here many times.
I believe I made the statement about there not being a deceleration until the object hits something which is more than strong enough to support it in reference to the steel cube falling through water and it would be accurate in that or a similar context.
You don't seem to mind taking someone out of context though, as besides the obviousness of your arrogance and pompousity you are indeed an insidious contorter of fact to boot.
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Tony Szamboti
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Why don't you quantify for me just what the durations and velocity losses are in the jolts you believe you found.
I'll have a go. Might not be in the *correct* terms, but am sure someone will iron out any terminology issues or wotnot.
As a trade, could you post the details on quantifying the maximum jolt magnitude/duration that a 0.200200... sample interval would not show. (Probably have to include the headroom between acceleration of the entity and free-fall in there somewhere, yes?) If I understand correctly, some of that has already been posted recently by WD Clinger, but it would be good to see a general equation which would relate sample interval, magnitude and duration.
If anyone else feels like replicating such detail, fine by me.
I imagine the *result* will have to be a function of magnitude/duration rather than a single value.
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Tony Szamboti
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Well...it's so small that varying smoothing methods alters the shape of the velocity reduction, but I suggest a *reasonable* approximation would be...
The large *mini jolt*...
Velocity reduction of 1.3 ft/s
Over a duration of 0.2s
The shape seems to increase in magnitude and decrease in duration the less smoothing is applied (which makes sense), so I'll also include...
Velocity reduction of 2.6 ft/s
Over a duration of 0.1s
...in the same breath for the same event.
I know it's a bit vague, but it's so small it's right down in the noise range.
The large *mini jolt*...
Velocity reduction of 1.3 ft/s
Over a duration of 0.2s
The shape seems to increase in magnitude and decrease in duration the less smoothing is applied (which makes sense), so I'll also include...
Velocity reduction of 2.6 ft/s
Over a duration of 0.1s
...in the same breath for the same event.
I know it's a bit vague, but it's so small it's right down in the noise range.
Grizzly Bear
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He proposes that the "lack" of any dynamic loading and of any rotation (tilt) are sufficient evidence that the strength was removed artificially. The former totally ignores conservation of momentum, while the latter destroys any supposition that the loads could have been eccentrically applied. The strength never had to be "removed." Just changing the load path can make a column buckle under normal loading.
He won't correct either, so his conclusions will remain invalid, no matter how much he proposes it.
This would be a great place to post evidence for such a thing. Do you have any?
(Couldn't edit for some reason)
ETA:...
And, yes, I'm aware of the large duration.
Thing to remember is it's the trend of the data, as it's averaged.
You could even say that during that period there are a couple of mini-mini-jolts, whose sum is a net velocity reduction.
Or you could go further and say that throughout the entire descent there are very many micro-jolts, and that during that time period their magnitude increased.
Depends upon how you look at it (as we're looking at very low-level).
I'm sure you'll not be happy with the *result* there, so as the data was taken using 6 month old tracing techniques, I'll see if I can increase the fidelity.
As suggested before though, to retain your current data (or indeed use any data set), it will be necessary to quantify the magnitude/duration function that the sampling interval/position sensitivity implies. (if that's in English
)funk de fino
Dreaming of unicorns
And now you are a paranoid liar!!
You do it incessantly.
You've had to "explain it many times" because you constantly confuse the two, and other people, who DO understand, have "called you on it many times".
You still don't get it, of course...
Sorry, bunky.
You brought up your stupid comment ("no deceleration until it hits something strong enough to support it") HERE while referring to the collapse of WTC 1.
I introduced the cube in water in direct response to your stupid contention HERE.
You contention is idiotically wrong in the context of the fall of the WTC towers. It is idiotically wrong in the case of a steel cube hitting water.
It is idiotically wrong in the case of two electrons colliding.
It is idiotically wrong in the case of two galaxies colliding.
It is idiotically wrong in the case of collisions between every single thing in between.
Your statement is a violation of the law (NOT the suggestion) of Conservation of Momentum.
Your comment would be idiotic coming from a poet. Coming from an alleged mechanical engineer, it lands smack dab in the middle of "ludicrously incompetent".
I noticed that you ignored my suggestion of finding your own expert to set you straight... Any particular reason for that?
I took nothing out of context.
The context is a universal law that applies to everything in the universe in every single collision.
The fact that you can't grasp the universality of the context is your personal short-coming.
LMAO, Tony.
I am certain that you considered the teachers who corrected your countless errors due to sloppiness & lack of comprehension "arrogant & pompous", too.
You just don't get it, do you?
Real engineers are NEVER concerned with "arrogance". Or "pompousity".
There is only one quality that matters: "right" or "wrong".
From your perspective, I can see how that would be a problem, tho...
___
So, figured out the CORRECT timing of the fall of the north external wall of WTC7 yet? Figured out where your statement was (oh-so-predictably) sloppy & wrong?
A dozen people here have led you by your little hand to the answer. Care to correct your statement?
(Or is it too pompous & arrogant of me to bring that up...?)
Tom
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I already posted the correct numbers HERE
The last column of that table is "percent of G".
Over the first 2.25 seconds, it rises, continuously & gradually, from 0% to about 85% of G.
___
If you want to do this with your own data, here is the RIGHT way to do it. (Most specifically NOT the way that Chandler did.)
Note that NIST, with access to REAL experts, found that the best that they could do with video footage (when trying to determine the speed of Flight 175) was ±6 feet. You might be able to get slightly better than this, due to smaller distances between the cameras & WTC7, but not much. And you don't have the knowledge or background of the professionals.
Get the best distance vs. time that you can. Generate an empirical equation. If your equation starts to diverge at the boundaries of your time of interest, then introduce an artificial control point well outside of the real data. Use this control point to draw your curve up or down, as needed to fit the raw data as best you can, and to keep it well-behaved.
If you can't get a single equation to fit all your data, do it with a couple of piece-wise empirical equations that have overlapping domains. Try to minimize any discontinuities in slope or magnitude as you transition between one curve & the next by using those artificial control points.
Then do your analytic single & double time differentiation for velocity & acceleration.
This will be the best representation of the "real" velocity & acceleration of the wall.
If you want to post your real data, I can do this for you in about 10 minutes.
An accurate error analysis - in integral part of any study - would take significantly longer. And requires knowledge of the performance details of the video camera systems, their positions, etc. From our discussions in the past, I am fairly convinced that you would not be able to execute this.
But you could get real close by using NIST's ±6' and then "scaling" the distances between camera & object. But only as long as you have video that is as high quality as that to which NIST had access. If you use compressed video, then the errors will be much higher.
____
Here is the germane point:
Look at NIST's 12-76 of NCSTAR1-9. (pg. 602 of Vol 2).
The raw data - the CORRECT raw data - is the downward displacement vs. time, taken from the videos. This is high quality data, as shown by the excellent quality of the fit all the way out to about 5.25 seconds.
The slope of this curve is also an excellent representation of the velocity at all points within the domain of the raw data (i.e., out to about 5.25 seconds). The last data point @ 5.4 seconds is off a bit.
Now look at Fig 12-77 on the next page.
The black curve is a plot of the calculated time derivative of the empirical curve in Fig 12-76. The QUALITY of this curve's reflection of the real value is given, NOT by any info in curve 12-77, but by the quality of the fit between the empirical curve & the raw data in Fig 12-76.
The single BEST representation of the "real" downward velocity is the black curve. All the way out to about 5.0 seconds. (Again, the empirical equation often starts to diverge at the edges of the data domain.)
The black dots in Fig 12-77 instantaneous velocity are NOT raw data. They are NOT "right". They are mediocre approximations calculated from the raw data.
The curve is a much better representation of the true downward velocity than black dots are.
This is why Chandler's refusal to provide his raw data is so egregious.
Now consider Chandler's "prize": his linear approximation.
He uses mediocre approximations to produce a POOR linearization. And produces no error analysis.
Excuse me for not getting all a-twitter about either his technique or his conclusions.
Tom
I'm aware of your post. Have you checked the NIST data ?
The noise level in my data is +/- 0.5ft
I even included the raw data graph, zoomed in so you can see. Perhaps you didn't click on it. I'll save you the bother...
Er, yup. Tick.
I prefer to use the actual data for derived values, even if the noise level increases. Can always be smoothed out.
If y'like. I'll post it in a bit. Ta.
Chandlers methods are pants.
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tfk said:
Here y'are...
Code:
Time(s) Drop (ft)
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Well, it's immediately clear that femr2's data is of inferior quality. His distance measurements have only nine significant figures, while the data posted on the previous page had thirteen! 
Respectfully,
Myriad
Respectfully,
Myriad
AZCat
Graduate Poster
- Joined
- Feb 6, 2007
- Messages
- 1,672
I think it's a sign of old age that I understand less and less of the slang you kids are using. What is "pants"?
Poor. Rubbish. Not good. Bad.ETA: Forgot about the USEnglish thing. Pants=Shorts=Undergarments.
Last edited:
W.D.Clinger
Philosopher
Well, it's immediately clear that femr2's data is of inferior quality. His distance measurements have only nine significant figures, while the data posted on the previous page had thirteen!
Myriad may be referring to the XML provided by Tony Szamboti, attributed to David Chandler, and posted by DGM. Although the y-value of each data point is expressed as an IEEE-754 double precision value with 17 digits, each of those values is an integral multiple of the quantum 480/1919 (approximately 0.2501302761855133), which probably derives from someone's estimate that the 480-pixel vertical resolution of the video corresponds to 1919 feet.
Multiplying 480/1919 by the following integers will reproduce the Chandler/Szamboti data to within 2x10-14, and even that slight error is probably caused by an imperfect output routine in the software they were using.
Code:
0
0
0
0
3
9
17
27
41
58
79
103
132
164
199
238
280
324
372
421
475If velocities are computed by balanced differencing, then the quantization error goes down by a factor of 2, but the resolution degrades by that same factor of 2, degrading the Nyquist frequency from 2.5 Hz to 1.25 Hz. In other words, balanced differencing might prevent us from seeing any direct evidence of a jolt lasting as long as 800 milliseconds.
We might be able to infer jolts that are a little briefer than that by looking at the velocity's recovery time, but to do that we'd have to know that free fall is 1g, not 0.7g.