Re: Physics Based Critique of the Petrov Method
Posted: Tue Mar 25, 2014 7:43 am
To CoachEric
1. I agree with your point fully and add that the “Rocket” analogy illustrates the conceptual need for continuous uninterrupted energy input throughout the pole support phases of the vault for the vaulter to be able to achieve their best launch trajectory at the instant of final pole release. This release point is in fact a second take-off except in this case the net impetus of the vaulter at this instant is the result of the restoration of some of the stored elastic potential energy due to pole bending caused by the continuous muscular efforts (useful work done) of the vaulter throughout the take-off and preceeding pole support phases. The recoil restoration to the maximum chord length possible and the spatial location and orientation of the vaulter’s body segments above the final hand grip release point provide the potential energy above the take-off surface. The linear and rotational kinetic possessed by the vaulter adds to that potential energy exchage. Note that the parabolic trajectory at the instant of pole release is fixed. The success or failure of the flight therefore relies on
A. the angle of projection of the vaulter’s total body centre of mass and total body segmental orientations and arrangements
B. magnitudes of the linear and rotational momenta of the vaulter and
C. the technical ability of the vaulter to manipulate their body part segmental relationships with respect to the trajectory of their total body centre of mass and their respective spatial locations relative to the cross bar.
2. Your request to clarify which of the two distinctly different take-off methods you interpret as part of the Petrov model is also echoed by me.
“In my opinion, the Free Takeoff is the correct result of the points emphasized by the model”. Coach Eric I concur with your opinion.
3. “An issue that this community remains split on, and which introduced this discussion, is the action of the arms post-takeoff. I believe I agree with your position that there is not a row, but a vigorous "realignment" into a hollow-body position, bringing the body in line with the chord of the pole, keeping pressure up on the pole with the bottom arm, accelerating the swing of the hips toward vertical. While I believe this technique to be correct, I don't have much basis to know for sure that this is part of Petrov's model. So, as with this example, please define more clearly what you believe to be part of the model that you are critiqing. For anybody to get smarter on this, we need to agree on what we're talking about.”
I also would like this (all of 3 above) to be clarified because willrieffer, in his latest post, dodges the
question in regard to presenting any actual physics that explains or supports his assertions in regard to
pole bend being induced whilst the take-off foot continues making ground contact in an “under” position
with respect to a vertical line between the surface of the runway and the top hand grip on the pole.
Some physics principles and facts to underpin these claims are necessary and would be
much appreciated!
To willrieffer
You said and I quote:
“The Petrov model got great success. It should be studied and used on that fact alone. It's just that having studied physics and in reading their and their disciples attempts at a physics based explanation, I see either poor efforts at explanation that do not agree with my knowledge of physics, or I'm left with a lot of questions.”
You went on to say:
”But for a bend take off vaulter they do have a chance to possibly add more energy. That's just physics. Is it enough to counter some of the problems in vaulting this way? I can't be sure.”
Just a moment! Let us pause for reflection here.
Your critique is “poor efforts of explanation”… “do not agree with my knowledge of physics” and you then go on to assert “a bend take-off vaulter can possibly put more energy into the vault due to pre take-off bending of the pole.” Your implication being a vaulter in so doing has an equal to or greater chance of a successful vault outcome compared to vaulters attempting to perform a “free take-off!
If the implication I have taken from your statement is correct then please tell us the physics of how and why this is so?
Will, you also stated and here is the quote:
“The free take off and/or its attempt almost in all cases would, I think, provides a higher/better angled force vector at take-off but eschews the possibility to add more energy. So the difference as I see it is in more energy versus better vector. … But again, from what I know of physics and the vault, if the free take off is "crucial", as Bubka claimed, then the method is giving up a possible energy source.”
What is it that you know from physics that convinces you that the ‘Free take-off” method is giving up a possible energy source?
In what way does a Petrov/Bubka free take-off eschew the possibility for the vaulter to add energy to the total pole plus vaulter system? (Great word choice “eschew”… wish I had used it first!).
However, I dispute that a “free take-off vaulter eschews anything and assert (on the basis of contributions made by me on PVP) but is actually enabled to amplify their capacity and opportunity to add input energy to the complex pendular system during foot contact and immediately after the take-off foot leaves the ground!
In your contribution to critique the Petrov Method so far I believe you have not yet identified the biomechanical and physics principles involved in the technique of how to induce pole bend and minimize input energy wastage that occurs when vaulters have to contend with long pole lengths between the top of the top grip hand and the pole tip and the consequent increase in the horizontal position along the runway to the take-off. The lower pole-ground angle such horizontal take-off distance from the rear wall of the planting box also poses an additional problem to be overcome in effecting a successfully completed vault.
The Petrov/Bubka Method was developed using biomechanical and physics based principles in the attempt to resolve these particular problems and equip the vaulter with techniques to pole vault high successfully, consistently and repeatability with relative safety when using long flexible high stiffness rating composite material constructed poles with long grip length along the pole to the vaulter's top grip hand..
Will, what your contribution highlights is the necessity to weigh up the costs and benefits involved in exploiting modern flexible poles by different take-off and swing techniques in relation to the physical
abilities and acquired capacities of a specific vaulter. This is commendable.
Have you actually gained sufficient familiarity with the total Petrov/Bubka Method to be sufficiently informed and therefore be in a position to critique the physics basis and rationale underpinning the method against your claimed understanding of Engineering Physics? I suspect not.
No matter what Model of the Vault a coach adopts and implements it is incumbent upon the coach to be, so far as they are able, to understand what they are coaching and put themselves in the position to be as sure as they can be that what they profess is “safe” and least likely to put young pole vaulter’s at unjustifiable risk!
What I like about your rather audacious physics critique of the Petrov/Bubka Method is that you have put yourself on the rack but show openness to having your perspective changed!
Since you also are actively engaged in coaching youngsters and providing them with an opportunity to participate in pole vaulting I appreciate the opportunity to respond to your questions.
That said I think you have not yet come through clearly to me in your posts as having really understood or appreciated much about the physics underlying the totality of the Petrov/Bubka method and approach to the coaching of flexible pole vaulting.
Fear not. You are not alone in this regard!
The thread you have established, so far, is covering previously well ploughed and sifted ground on PVP.
Coach Eric is right in stating what PVP coaches want in regard to the Petrov/Bubka approach to vaulting with flexible poles is clarification of the role of the lower arm post take-off and the physical and biomechanical rationale underlying the claimed action roles in the generation and maintenance of swing induced energy input throughout the pole bending/buckle and recoil phases.
Finally, I think that when you have read more and have fully digested the Petrov/Bubka Approach you will find either your knowledge of the physics of pole vault was more limited than you thought or you will become even greater in confidence that your physics understanding is correct and that this approach is as you claimed in your opening to this thread. I do request that you give the physics reasons as you understand them for the claims and assertions you make.
This thread will be all over the internet as “Physics Based Critique of the Petrov Method of Pole Vault!” Will, it is incumbent upon you to put up the physics evidence that definitively falsify or cast serious doubts upon the principles espoused in the Petrov/Bubka Model of Pole Vault. If this thread is simply to be questions and answers concerning the Physics foundations of the Petrov Method then I think the inclusion of “Physics Critique” in the thread title is clearly not justified.
I will stop this post here because in the last posts of yours in regard to pole chord shortening etc., a plethora of issues arise in regard to a human’s double pendular motion, moments of inertia of vaulter and moments of inertia of the total system centre of mass, energy and momenta conservation laws with respect to the timing of momenta directional changes, energy inputs and exchanges that need to be sorted out. That is a big task!
1. I agree with your point fully and add that the “Rocket” analogy illustrates the conceptual need for continuous uninterrupted energy input throughout the pole support phases of the vault for the vaulter to be able to achieve their best launch trajectory at the instant of final pole release. This release point is in fact a second take-off except in this case the net impetus of the vaulter at this instant is the result of the restoration of some of the stored elastic potential energy due to pole bending caused by the continuous muscular efforts (useful work done) of the vaulter throughout the take-off and preceeding pole support phases. The recoil restoration to the maximum chord length possible and the spatial location and orientation of the vaulter’s body segments above the final hand grip release point provide the potential energy above the take-off surface. The linear and rotational kinetic possessed by the vaulter adds to that potential energy exchage. Note that the parabolic trajectory at the instant of pole release is fixed. The success or failure of the flight therefore relies on
A. the angle of projection of the vaulter’s total body centre of mass and total body segmental orientations and arrangements
B. magnitudes of the linear and rotational momenta of the vaulter and
C. the technical ability of the vaulter to manipulate their body part segmental relationships with respect to the trajectory of their total body centre of mass and their respective spatial locations relative to the cross bar.
2. Your request to clarify which of the two distinctly different take-off methods you interpret as part of the Petrov model is also echoed by me.
“In my opinion, the Free Takeoff is the correct result of the points emphasized by the model”. Coach Eric I concur with your opinion.
3. “An issue that this community remains split on, and which introduced this discussion, is the action of the arms post-takeoff. I believe I agree with your position that there is not a row, but a vigorous "realignment" into a hollow-body position, bringing the body in line with the chord of the pole, keeping pressure up on the pole with the bottom arm, accelerating the swing of the hips toward vertical. While I believe this technique to be correct, I don't have much basis to know for sure that this is part of Petrov's model. So, as with this example, please define more clearly what you believe to be part of the model that you are critiqing. For anybody to get smarter on this, we need to agree on what we're talking about.”
I also would like this (all of 3 above) to be clarified because willrieffer, in his latest post, dodges the
question in regard to presenting any actual physics that explains or supports his assertions in regard to
pole bend being induced whilst the take-off foot continues making ground contact in an “under” position
with respect to a vertical line between the surface of the runway and the top hand grip on the pole.
Some physics principles and facts to underpin these claims are necessary and would be
much appreciated!
To willrieffer
You said and I quote:
“The Petrov model got great success. It should be studied and used on that fact alone. It's just that having studied physics and in reading their and their disciples attempts at a physics based explanation, I see either poor efforts at explanation that do not agree with my knowledge of physics, or I'm left with a lot of questions.”
You went on to say:
”But for a bend take off vaulter they do have a chance to possibly add more energy. That's just physics. Is it enough to counter some of the problems in vaulting this way? I can't be sure.”
Just a moment! Let us pause for reflection here.
Your critique is “poor efforts of explanation”… “do not agree with my knowledge of physics” and you then go on to assert “a bend take-off vaulter can possibly put more energy into the vault due to pre take-off bending of the pole.” Your implication being a vaulter in so doing has an equal to or greater chance of a successful vault outcome compared to vaulters attempting to perform a “free take-off!
If the implication I have taken from your statement is correct then please tell us the physics of how and why this is so?
Will, you also stated and here is the quote:
“The free take off and/or its attempt almost in all cases would, I think, provides a higher/better angled force vector at take-off but eschews the possibility to add more energy. So the difference as I see it is in more energy versus better vector. … But again, from what I know of physics and the vault, if the free take off is "crucial", as Bubka claimed, then the method is giving up a possible energy source.”
What is it that you know from physics that convinces you that the ‘Free take-off” method is giving up a possible energy source?
In what way does a Petrov/Bubka free take-off eschew the possibility for the vaulter to add energy to the total pole plus vaulter system? (Great word choice “eschew”… wish I had used it first!).
However, I dispute that a “free take-off vaulter eschews anything and assert (on the basis of contributions made by me on PVP) but is actually enabled to amplify their capacity and opportunity to add input energy to the complex pendular system during foot contact and immediately after the take-off foot leaves the ground!
In your contribution to critique the Petrov Method so far I believe you have not yet identified the biomechanical and physics principles involved in the technique of how to induce pole bend and minimize input energy wastage that occurs when vaulters have to contend with long pole lengths between the top of the top grip hand and the pole tip and the consequent increase in the horizontal position along the runway to the take-off. The lower pole-ground angle such horizontal take-off distance from the rear wall of the planting box also poses an additional problem to be overcome in effecting a successfully completed vault.
The Petrov/Bubka Method was developed using biomechanical and physics based principles in the attempt to resolve these particular problems and equip the vaulter with techniques to pole vault high successfully, consistently and repeatability with relative safety when using long flexible high stiffness rating composite material constructed poles with long grip length along the pole to the vaulter's top grip hand..
Will, what your contribution highlights is the necessity to weigh up the costs and benefits involved in exploiting modern flexible poles by different take-off and swing techniques in relation to the physical
abilities and acquired capacities of a specific vaulter. This is commendable.
Have you actually gained sufficient familiarity with the total Petrov/Bubka Method to be sufficiently informed and therefore be in a position to critique the physics basis and rationale underpinning the method against your claimed understanding of Engineering Physics? I suspect not.
No matter what Model of the Vault a coach adopts and implements it is incumbent upon the coach to be, so far as they are able, to understand what they are coaching and put themselves in the position to be as sure as they can be that what they profess is “safe” and least likely to put young pole vaulter’s at unjustifiable risk!
What I like about your rather audacious physics critique of the Petrov/Bubka Method is that you have put yourself on the rack but show openness to having your perspective changed!
Since you also are actively engaged in coaching youngsters and providing them with an opportunity to participate in pole vaulting I appreciate the opportunity to respond to your questions.
That said I think you have not yet come through clearly to me in your posts as having really understood or appreciated much about the physics underlying the totality of the Petrov/Bubka method and approach to the coaching of flexible pole vaulting.
Fear not. You are not alone in this regard!
The thread you have established, so far, is covering previously well ploughed and sifted ground on PVP.
Coach Eric is right in stating what PVP coaches want in regard to the Petrov/Bubka approach to vaulting with flexible poles is clarification of the role of the lower arm post take-off and the physical and biomechanical rationale underlying the claimed action roles in the generation and maintenance of swing induced energy input throughout the pole bending/buckle and recoil phases.
Finally, I think that when you have read more and have fully digested the Petrov/Bubka Approach you will find either your knowledge of the physics of pole vault was more limited than you thought or you will become even greater in confidence that your physics understanding is correct and that this approach is as you claimed in your opening to this thread. I do request that you give the physics reasons as you understand them for the claims and assertions you make.
This thread will be all over the internet as “Physics Based Critique of the Petrov Method of Pole Vault!” Will, it is incumbent upon you to put up the physics evidence that definitively falsify or cast serious doubts upon the principles espoused in the Petrov/Bubka Model of Pole Vault. If this thread is simply to be questions and answers concerning the Physics foundations of the Petrov Method then I think the inclusion of “Physics Critique” in the thread title is clearly not justified.
I will stop this post here because in the last posts of yours in regard to pole chord shortening etc., a plethora of issues arise in regard to a human’s double pendular motion, moments of inertia of vaulter and moments of inertia of the total system centre of mass, energy and momenta conservation laws with respect to the timing of momenta directional changes, energy inputs and exchanges that need to be sorted out. That is a big task!