https://www.youtube.com/channel/UC5B8gE ... h6wwEBX7_Q
I don't know which method they used for measuring the velocity, probably video analysis as I don't see any infrared timing gates, but the numbers seem reasonable.
Have fun!
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willrieffer wrote:In another thread grandvaulter posited that two vaulters of different heights would free swing at the same velocity. This is against well established principles of physics. They may indeed swing at the same speed (and where he used his eye to tell me they did), but not "freely". The natural movement of the shorter vaulter would be to progress faster through the angle...
willrieffer wrote:It's pretty simple really, but hey, feel free to fall on your sword if ignorance again there gv...
grandevaulter wrote:willrieffer wrote:In another thread grandvaulter posited that two vaulters of different heights would free swing at the same velocity. This is against well established principles of physics. They may indeed swing at the same speed (and where he used his eye to tell me they did), but not "freely". The natural movement of the shorter vaulter would be to progress faster through the angle...
I stated that they moved at the same speed on different scales. I don't believe that my practical observation has been scientifically proven inaccurate. Give it a shot Will.willrieffer wrote:It's pretty simple really, but hey, feel free to fall on your sword if ignorance again there gv...
I probably will fall on my sword after I trip over our two state championship trophies and one runner up in the last three years.
PVstudent wrote:"It's here that we find that if we look at WC shorter vaulters like Lavillenie, Dial, Greg Duplantis, Jeff Buckingham, etc, you find they are all lead arm lockers. Why? Because they have to do so to stop swing progression where swing progression is where the COM rotates forward lowering pole compression and causing the vault to fail or be infringed."
What does this actually mean?
Define lead arm-lockers.
“…where swing progression is where the COM rotates forward lowering pole compression and causing the vault to fail or be infringed.”
It is very difficult to understand what the COM is doing if no axis for rotation is identified. Rotates forward? Do you intend the reader to understand that the COM is rotating, implying that it is actually spinning about an axis through the COM?
Or do you mean that whilst the COM is undergoing translation forwards in direction in the sagittal plane toward the landing pads it is also being simultaneously rotated about the pole tip transverse axis located in the planting box as well as being rotated in the opposite direction about the upper and lower grip transverse axes at the other end of the flexing pole due to the weight and swinging action of the vaulter?
“This has almost NOTHING to do with force or pressure on the pole at the lead hand. Yes, it will feel like pressure and there MUST be an active/reactive force, but the important part of what it does is press or hold the COM back...which is part of the PB method! It was imperative to keep the COM/hips back!”
Two points
1. Is holding the COM back actually espoused and advocated by either Petrov or Bubka?
I have had extensive contact with, coached alongside Petrov, have resided in Formia for extended periods whilst my vaulters (World Class level vaulters) were coached and trained in Formia by Petrov and accumulated comprehensive notes and video materials on the Petrov-Bubka Model of Pole Vault.
None of the experiences and learning at first hand from Vitali Petrov has revealed to me that he has ever advocated or insisted that the vaulter “… press or hold the COM back” which you claim / assert is part of the PB method.
2. The role of centripetal force is being misinterpreted by your claim referring to Messrs Lavillenie, Dial, Duplantis (Greg),Buckingham etc., when you make this assertion:
“It's here that we find that if we look at WC shorter vaulters like Lavillenie, Dial, Greg Duplantis, Jeff Buckingham, etc, you find they are all lead arm lockers. Why? Because they have to do so to stop swing progression where swing progression is where the COM rotates forward lowering pole compression and causing the vault to fail or be infringed.”
My Comments for Consideration:
Since the vaulter is attached to the massive earth by the pole, centripetal force generated by the muscle work done by the vaulter in creating swing around both swing axes (namely Pole tip in the box and the grip axes) with the vaulter suspended below the grip axes vigorous swinging will provide additional pole bending moments to that created by vaulter’s weight force.
By stopping or reducing the angular acceleration of the vaulter’s swing by “holding the COM back” reduces the centripetal force contribution to the pole bending moments of force. This has two undesirable consequences.
Consequence 1 reduction in pole chord angular velocity about the pole tip axis because there will be little or no angular momentum contribution from the vaulter swing as holding back is trying to create the same effect as a simple suspended “dead weight” below the hands. This negates some of the total system (Vaulter + Pole) angular momentum about the pole tip axis generated at take-off. Total system penetration rate towards the plane of the cross bar is thereby reduced.
Consequence 2 Retarding the vaulter’s swing acceleration and reducing centripetal force to keep the COM “lower” with respect to the pole tip axis increases or maintains the vaulter’s COM in a position relative to the grips that increases the moment of inertia about the hand grip pivots. The delay or pressing back of the COM increases the vaulter muscular torque required to initiate or create the swing angular velocity from a “dead hang” or “low rotational speed” about the grip pivots because of this larger moment of inertia about the grip axes.
The two consequences alluded to above get to the heart of the “Double Pendulum Challenge” that faces a pole vaulter once airborne in the first phase of vaulting.
All vaulters solve this “Double Pendulum Challenge” optimization problem in phase 1 of pole support to be successful in a pole vault jump clearance. What the optimal solution is can only be solved by a specific vaulter, in a specific vault attempt in a specific psychosocial-cultural and physical environment context.
The optimization requires multiple interacting parameters to be resolved.
These parameters produce both linear and nonlinear interactions.
Fortunately most vaulters employ an empirical learning of this optimizing process guided by their own efforts and input feedback from a coach.
Athlete and Coach use the tried and true “Suck It and See What is Just About Right!” method of Goldilocks.
This is doing by practice in the “Arts” of pole vault learning and coaching. The practice process can be informed by science but it is not science!
The performance of the art can of course be studied and subjected to analysis using Newtonian Mechanics Principles by scientists.
“When PV Student did his "box force" experiment and found a higher force by differing method it was extrapolated as being an infringement without taking every possible physics possibility into consideration. This is why he's more politician than scientist. A force at one end is going to end up at the other. SO the vaulter is going to experience higher pole braking which is the point at which he stopped his analysis because it offered the result he had set out to find the beginning(for any physicist this result such was so simplistic as to be given from a brief thought experiment!) . This COULD cause the vaulter to be thrown forward, which we all AGREE is a problem for both my ideas and the PB model. Yet it also means that the pole is taking on more energy, faster, bending more and shortening the chord faster which would, or can reduce its length and with all other things being equal, speed is rotation. But this idea was never addressed (neither has the "free" take off versus drive energy idea). Which is why we have a political argument and not a scientific one...and it continues. For the COM movement one would need to do a comparative study, not just post one graph (which would only be the scientific starting point) and then follow with a political argument. But its easier to be a politician with a gang than do good thorough science...”
This is not only inaccurate, misrepresenting what I have done in regard to measuring forces under the pole via transducers in the pole planting box but demonstrates yet again the correspondent’s inability to understand or communicate, or both, what I have actually stated.
The contributor’s attempted critique of my work does not convey in any cogent manner what it is that he finds so simplistic.
He is unable, as best as I can decipher from the above, to clearly and cogently describe where, when, what and why my contribution/s is/are or have been so simplistic and wrong.
If I’m wrong about something I will be the first to acknowledge my mistake/s when the mistake is clearly and explicitly explained to me. I am always ready and eager to learn.
The attempt to belittle with “This is why he’s more politician than scientist.” and “But it’s easier to be a politician with a gang than do good thorough science...” does not need any rebuttal from me!
I am not going anywhere near objects with sharp points or hoisting myself with my own petard and so, without any reluctance, relinquish my place at the discussion table.
I am happy to stay firmly grounded in the near enough is good enough Newtonian Earth World where basic mechanics principles operate quite well.
Bon Voyage Will on your trip through the nebulous “Black Hole” you are creating!
willrieffer wrote:The problem is that you think there needs to be a "scientific" response to your practical observations. That's not how "science" works, or, you're working backwards. In this, the property of pendulums is proven science which YOUR observation goes against. OR, again, the point of proof is yours.
Indeed I say they CAN swing at the same speed, but only if they are actively regulating the swing speed.
willrieffer wrote:In another thread grandvaulter posited that two vaulters of different heights would free swing at the same velocity. This is against well established principles of physics. They may indeed swing at the same speed (and where he used his eye to tell me they did), but not "freely". The natural movement of the shorter vaulter would be to progress faster through the angle...
PVstudent wrote: The 3-dimensional space curvilinear pathway (since the radial distance from the pole tip axis to Stickman's hips (COM) is not a constant radial length varying continuously with respect to time from Stickman's Take-off to 180 degrees of inversion) must also be taken into account.
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