Bubka's Energy transfer

[Lefty]

Hey dude, I'm a bit of a physics nut and a vaulter. Here is a cool paper I found about takeoff efficiency:

http://pukashell.net/kimo/polevault/linthorne.pdf

Also, it might be useful to try to find some of the articles in its references, but most of the publications are pretty obscure.

Based on my knowledge of physics and the vault (15'9" PR... hopefully higher soon!) there isn't really too much you can do to add energy during the vault. When people talk about adding energy to the system what they are actually talking about is converting energy from one form to another (translational kinetic into rotational kinetic, spring potential, and gravitational potential) with maximum efficiency. The swing doesn't really "add energy to the system." About the only energy you can put into the system is during the pull and the push-off.

I will explain my reasoning for this. Once you leave the ground, you and the pole together make up a system that is in contact with its surroundings only at the point where the pole tip touches the box. Internal forces in this system cannot add energy (in any way) to the system due to Newton's third law (equal and opposite reaction). The only way to change the energy of the system is to apply a force such that it is applied at the boundary of system (the box) onto the surroundings. If you do this at any point before the pole is vertical, it will have an adverse affect because the only direction this force can be directed is back towards the runway. But once the pole is vertical, the vaulter can then apply a pulling force and finally a pushing force against the box and thus add some energy (gravitational potential in this case) to the system.

So basically what I am saying is that the kinetic/potential approximation is fairly accurate (once you take into account the initial height of the center of mass for the system), with the only additional height gained essentially by doing an upside-down pull up while in the air.

Hope this helps. If you have any questions or anybody wants to debate/prove me wrong, please do. I love thinking about this kind of stuff.

[dj]

hey

i should have said increase in vertical speed..

rotational speed around the shoulders and top hand.. creates ?

dj

[vault3rb0y]

Well not technically add energy but i do believe transfer the force of your swing into the pole. When you swing with any velocity around your top hand, it creates centripital acceleration (Ac=V^2/R). Then your body weight X that acceleration= the force (F=MA), or extra tension, added onto your top hand and down on the pole. Obviously the farther your body weight (hypothetically keep in mind) from your top hand, the more force you will create. Now the only way to properly add the energy is to set up to add this energy before the pole hits the back of the box. Any trail leg movement backwards AFTER the pole has hit the back of the box is actually releasing tension on the pole, and is then cancelled out again as you swing through. At that point i believe, like you said, you have entered the vaulter-pole system and you cannot add energy because of newtons laws. But what if you put energy into the ground at take off, and set up your swing, BEFORE you enter the vaulter-pole system (free take-off/ pre-jump)? I believe you can add the potential energy you have created off the ground by hitting an inverted C, into the pole with a strong swing.

Imagine you are on a thick bungee cord that will react up and down according to your swing. You swing your trail leg back, and the tension of the bungee is released. This is what happens when a vaulter brings his trail leg back AFTER he/she already enters the vaulter-pole system. The bungee actually contracts a little as you lift your trail leg behind you. Then you swing through, and do a bubka. The bungee expands again as you have added tension to it again. Its the same thing on the vault. Unless you are already in an "inverted C" and prepared to swing before the pole hits the back, you will have a hard time increasing the tension of your swing. Now imagine you are standing on the ground and jump into the air, putting your body into an inverted C, THEN grab the bungee and swing. The bungee is not having to absorb the energy of getting into your inverted C, because you did that before you were in the system.

Now keep in mind, this is something ive just recently had on my mind so i might not be right. This physics project is opening up my mind, even if my teacher has no idea what im talking about!! LOL

[vault3rb0y]

Also i would note, it is not impossible to add additional energy if you plant under (and therefore hit your inverted C while on the vaulter pole system). However, it will only happen if you swing forward with more acceleration than you swung backwards into your inverted C position originally, and if you swing forward for a longer period of time. The energy is coming from your muscles contracting, not from pulling energy away from the vaulter-pole system.

Again just some new thoughts of mine.

[Lefty]

Hey, all good thoughts.

Thinking about my analysis some more (at vault practice today...), I see that one part of my analysis was flawed. Initially, the force of the box on the tip all basically in the x-direction, so my argument about external forces is true. But soon after the pole begins to bends there will be an x-component and a y-component of the resulting force on the pole tip. This would allow some of the work done by your muscles to add energy to the system.

And after a little bit of coaxing, google was willing to cough up this article:

super duper article

It is essentially exactly what you are trying to write about. They use some pretty complicated math in their analysis, but the great thing about academia is that now that they have done it, you don't have to! (you can just cite their work)

[vault3rb0y]

Thanks, i actually handed my paper in today (LOL). The purpose wasnt to create a perfect scientific observation that contributes to the scientific community, but to get a feel for how to write a paper. I just went above and beyond since i am interested in this field of work. Thanks for all the input and studies, i have a deeper understanding of the vault myself, having written about it! I guess its true when they say sometimes the best way to learn things is to try to explain it to someone else. You end up asking questions you didnt think of before.

[altius]

Now that is settled, perhaps someone can tell me - as a mere coach - why the 'swing' was seen to be critical by stiff pole vaulters, and why - if you cannot put energy into a system using a 'swing', children manage to get their "swings" above the vertical and why trapeze artists work hard to increase the speed and amplitude of their swings as they prepare for a quadruple back somersault?

In neither of these situations does the energy involved come from a run up and take off -so where does it come from???

[Tim McMichael]

I wish we could put this one to rest. Muscles are an energy system in themselves and are not dependant on any factor other than their own ability to contract. If done correctly this adds energy to the vault. A vaulter should penetrate more on the pole when they complete the jump than they do when they plant and hang.

[vault3rb0y]

Actually im a little confused on how it helped stiff polers OTHER THAN the continued motion of the hips helped them move their hips 2 feet over their handhold. The tuck and shoot on a stiff pole would be very choppy and not very fluid. But it seems like it would be hard to swing on a stiff pole and effectively increase your top hand hold by doing so. If the goal is moving the pole to vertical, i dont know how swinging on a stiff pole helps yet.

[powerplant42]

For the same reason it works on a flexible pole. (Remember, all a flexible pole should be thought of as is an infinite series of stiff poles!)

[master]

Hey, all good thoughts.

Thinking about my analysis some more (at vault practice today...), I see that one part of my analysis was flawed. Initially, the force of the box on the tip all basically in the x-direction, so my argument about external forces is true. But soon after the pole begins to bends there will be an x-component and a y-component of the resulting force on the pole tip. This would allow some of the work done by your muscles to add energy to the system.

And after a little bit of coaxing, google was willing to cough up this article:

http://www.sciencedirect.com/science?_o ... ea4f1#tbl1

It is essentially exactly what you are trying to write about. They use some pretty complicated math in their analysis, but the great thing about academia is that now that they have done it, you don't have to! (you can just cite their work)

When you want to post a long url, it won't force the use of a horizontal scroll bar if you do it as is shown in the code box.

Code: Select all

[url=http://xyz.aslonganameasyoucanwrite.com/evenmore.htm]descriptive text here[/url]


Your url could then be very short and still achieve the same thing.

You can edit your post to see the difference it makes. Just use the edit button in the upper right corner of your post, change it in the text entry box, the click on the submit button.

- master

[vault3rb0y]

Ok then powerplant, in what form is the energy converted? Your swing on a flexible pole is stored in the pole in the form of stretching and compressing fiberglass. If your swing is adding energy into the vaulter pole system, what form does it take?

Also Tim, im curious if you know the distance from Joe's top hand hold to the bottom of the box at its largest bend. Basically, as high as he would have been able to hold while stiff poling. Id like to know how that compares to the other 19'7" jumpers top stiff-pole hand holds like bubkas 4.20 (i believe?).