Can you add energy after takeoff?

[KirkB]

Bel posted this in the Intermediate forum here http://polevaultpower.com/forum/viewtopic.php?f=37&t=17490 in the "Turning Over/Speed thread ...

... the run sets up the majority of the energy used for the rest of the vault. You can not add energy into the vault once you have left the ground. (now for all those who are growling at your computer screens... let me explain) One you leave the ground, all that is left is physics,

energy in = energy out - the petrov model helps transfer energy to the pole then back to the vaulter in a very efficient way and making the transfer much easier.

Since I'm growling at you about this, (not my screen ), I'd like to challenge you on your statements ...

Everyone with an opinion please vote on this.

I say of COURSE you can add energy into your vault by your actions on the POLE after takeoff!

If your swing is fast enough, it can add energy, and if your extension is quick and powerful enough, it can add even more energy.

Why would you think anything differently?

Kirk

[altius]

Why do we bother??? I am not going through this AGAIN!

[IAmTheWalrus]

Bel is looking at this the wrong way. if we were looking at some arbitrary point mass like we so often do in intro mechanics courses, then the statement would be correct. The Kinetic Energy produced by the run up and takeoff is absorbed by the pole and redirected vertically resulting in an equivalent (minus energy lost through the transfer) gravitational potential energy, aka height.

However, a human body is not a point mass or a block or a rod, and it has the ability to exert forces on its environment. The body has additionally potential energy in the muscles (which is why you don't need someone to push you down the runway). Have you ever watched someone on the high bar? They are able to not only swing their entire body around the bar, but do so with enough energy to perform release maneuvers several feet above the bar. They are capable of raising their center of mass several feet without a run, takeoff or even a flexible pole. If you look at the vault in a similar way, you can see that while the run and takeoff provide the initial energy to get the vault started, the swing adds energy to the pole, and raises the vaulters center of mass.

Also, it's interesting to note that the Fosbury flop actually allows the jumper's center of mass to travel beneath the bar. The same (I imagine) is true with a pole vaulter piking over the bar. This means that for those of you who use Kinetic energy equations to calculate how high you can vault, you can probably add more height because your COM is traveling under the bar.

Take it easy everyone.

[Erica]

Have you ever watched someone on the high bar? They are able to not only swing their entire body around the bar, but do so with enough energy to perform release maneuvers several feet above the bar.

Imagine them trying to complete a giant from a still hang...

They have to do something to create the energy necessary for the giant and the release. They put themselves in the posision to use gravity to it's fullest...the gymnast with the most air on the release or greatest velocity through the giant is the gymnast who minimizes the energy loss the most. Same in the pole vault, otherwise we could just vault without the run...

[powerplant42]

Now think about THIS...

Hanging on a bar, how do you create the energy to start swinging? It's certainly not transferring energy from a run. And how do you accelerate the swing once you get it going? ENERGY IS ADDED BY THE MUSCULAR SYSTEM! Chemical energy (ATP and the like) + potential energy (pre-stretch) ----> kinetic energy! Right? (Close, at least...)

[IAmTheWalrus]

Thank you PP, that's the point I was trying to make.

[vault3rb0y]

I think he's getting at the point that you dont add energy, you redistribute it from your muscles, to the swing action of your body, into the pole. In that sense, there is a limited amount of energy that can be added, limited only by the strength of your muscles and your body type. I know for a fact that bel knows that it is possible to add energy, and that it's a matter of technicalities in what is actually happening to "add" that energy. If i am wrong he will be on here to correct me.

[KirkB]

You're all correct in asserting that you can add energy in both the swing and extension phases of the vault.

And you're correct in saying that it comes from "muscle power" (to dumb it down a bit).

One thing I'd like to make perfectly clear ... and I think this is already clear to the posters on this thread ... but maybe not to younger readers (PP excluded) ... is that once you leave the ground on takeoff, your vaulter-pole system's energy is not PRE-DETERMINED.

That is, it's not the same situation as being in outer space, and trying to ... let's say accelerate your body in a certain direction.

In the space scenario, you have no TRACTION to push against ... to move your body or accelerate. Every action has an equal and opposite reaction (according to Newton), so if you try to manipulate your body in a certain direction ... with the intent of ACCELERATING in that direction ... you will just ROTATE your body ... your CoM won't move ... and you won't MOVE in the direction intended. You need an outside force to make that happen.

Typically, a spaceman outside the space-station will use back-pack jets, and the force of the jets in one direction will accelerate his body in the opposite direction. Don't ask me what "object" these jets push against, since space is just "space" (as far as I know), and if you push against "empty space" then how can there by any TRACTION? However, I'll leave that aside, since I don't understand the details of how jet propulsion works in outer space (as opposed to within the Earth's atmosphere, where it pushes against AIR).

In the PV scenario, you have an ANCHOR to push against. That anchor is the pole in the box. That changes the scenario entirely! It's not like the outer space scenario at all! So when you manipulate your body in a certain direction, the downwards force into the box is opposed by equal and opposite upwards forces in whatever way you're manipulating your body ... during the swing and the extension.

So as long as you have a firm ANCHOR to push against ... since the box is immobile ... you have sufficient TRACTION to ADD energy to the vaulter-pole system.

I hope everyone understands and agrees with this ... it's basic physics.

Kirk

[bel142]

Jeez I just about got called out.... Its late and I am trying to pack for a meet out in ohio now, but I can't resist the great debate... I can sleep on the bus...

I am going to stay away from adding energy talk, because if you block your self out the jump ends and you get stood up... You swing and the vault works... you combine those energies together yes.... But in terms of energy not being pre determined, I honestly disagree, all things in the vault being added up leaves with a very specific finite amount of energy to be used. Once you leave the ground, if everything went perfectly, angles, maximum swing, muscle contractions, (everything else you can imagine)... One is not able to exceed 100%... (talking in hypotheticals) when the vaulter can not do anything else better, or change anything else. He/she is tapped out. There is nothing one can do to increase height (this is not the world we live in), this includes ground reaction forces. (and i am taking that sound-bite of information from Hartwig's interview on pole vault world) Ground reaction forces are equal to that of what happens. You hit the earth (the box) it will hit you back with exactly how much you hit it with...

For example, if you were to slam a bouncy ball on the ground it will bounce and recoil to the amount put in, and absorbed back from the ground. Hence you can slam a bouncy ball down from about head height, and it will recoil much higher. Energy transfer is never 100%, if it were then the ball would just keep bouncing, because the recoil and fall would equal each other (sans air resistance and such).

At this point I think simple physics and Newton's law is all we can go on... If we lived in a perfect world, the fastest vaulter with the perfect pendulum and perfect technique for energy transfer, those all being variables, a specific vault height would ensue... now because we don't live in a perfect world, athletes start to loose bits of energy through technique and such, when athletes who start to do more of those variables more correctly getting more close to 100% this is when we start to see records being broken.

If the vault was not predetermined when the vaulter left the ground, this would allow for vaulters to jump past what the laws of physics allow. People enjoy their method of pole vault for specific reasons, but guys who don't jump well, still jump high, and that is more of the punch line in the sport of limits of the human body.

[KirkB]

If the vault was not predetermined when the vaulter left the ground, this would allow for vaulters to jump past what the laws of physics allow.

Whoa Nellie!

Bel, I can see that you just "don't get it" yet. [sigh]

You wrote a lot of words, but all I got out of what you said is that once you leave the ground, the most you can possibly hope to achieve is to apply every last morsel of energy that you've already generated in your run and takeoff to your swing, extension, and fly-away over the bar ... without losing any energy ... except to the pull of gravity.

In other words, you're saying that if your energy at takeoff is 100% (since you haven't LOST any energy yet), then if you don't lose any energy due to inefficiencies in your vault, then all you can get back off the top of the pole is that same 100%. You're saying that anything greater than 100% is a mathematical impossibility. Is that your position?

But I just explained to you that this would only be true in outer space, when you have nothing to push against.

I buy your argument if you're a long jumper. They have nothing to push against after takeoff to make them jump further. But we do. As long as the pole is anchored to the box, you're able to push against the ground, just as on a highbar.

The highbar is anchored to the ground so if you manipulate your body against the highbar, you can do giants, shoot-to-a-handstand, release tricks off the top of the bar, and all kinds of other tricks. All this from a hanging start. A simple kip-up from a hanging start proves that you can generate additional energy once you leave the ground.

You just lift your legs, cast a bit to generate some swing, then go "arch to hollow", and do your kip. Now you're in a static position with your hips on the bar. You raised your potential energy by several feet ... all with sheer muscle-power! All from a static hang under the bar!

Your muscular actions add energy to the gymnast-highbar system, just as your muscular actions in the vault add energy to the vautler-pole system. Don't you get that?

If what YOU say is true, then you should not use your muscles at all. Instead, you should only use your skeletal system and tendons ... to minimize energy leakage.

While there's a huge advantage in swinging long and minimizing your muscular actions in SOME parts of the vault, you can't take this argument to the extreme. You shoudn't just "swing long". Instead, you should cause your downswing to accelerate as quickly as possible, so that it hits its maximum speed when you pass the chord. Otherwise, you're just "coasting", which doesn't add any energy.

Are you advocating just coasting during the downswing, or do you see the merit in accelerating your swing ... thru muscular actions. Not only "slight" muscular actions, but "vigorous" muscular actions ... from hand to toe!

Have I convinced you re the swing yet?

Let's move on to the extension ...

If muscular action does nothing, then you must be advocating just "freezing" in an inverted position and "riding the pole". Let's even sidestep the fact that the only way to get inverted is thru some muscular action. Or are you saying that by just "hanging onto the pole", you'll swing completely upside down into an inverted position without any additional muscular effort?

BTW, even "freeezing" takes some muscular energy, so I guess you're thinking that you need to exert enough muscular energy in this frozen positition (which would be passive, BTW) to stay inverted. Is that it?

Well, if you're going to spend some energy in freezing in this position (sounds like a tuck to me), then why not spend some MORE energy, and shoot out of that frozen position ... in unison with the pole? Even tuck shooters do that ... and when they do, they're adding energy to the system ... believe it or not!

Can't you see how the straightening of your torso, back, and shoulder muscles as you accentuate your extension, causing you to add energy to the system?

Have you got it now? ... or not?

If not, I've run out of words, and someone else will have to try to explain it. [sigh]

Kirk

[bel142]

No, I do not negate the fact that muscular contraction is apart of the vault. Actually at this point I am not sure what we are discussing. Musculature affects the vault yes. Absolutely, other forces affect the body, pole tip friction, air resistance, gravity.

If we think about the vault in parts (and I am not trying to do that) I think one would be able to get more than the original 100% out of the pole. However, if we think about the vault as one action, it is not possible, but once net forces applied to the body, are enough to take the body of mass off of the pole, triceps extension still is affect movement, however my point (if this was the questions) actin/myosin cross bridges still also have potential energy stores that have limits. If we think about the vault in that same degree, one is not adding anything, so much as it was, already in the mechanical system.

Once net forces push the body off the pole energy has already been transfered and now the pole is inactive and the human body is pushing against the pole, pushing against the world. At this point it is reasonable to think about triceps extension adding energy.

I am personally thinking about the vault in two regards, one, at take off moment by moment calculations, as if a high speed camera was used and frame by frame is used, and second end results energy conversion. Everything is already set up to supply maximum results, and that 100% conversation changes as moment to moment continues. The second regard, at the end of pole/body manipulation.

[VaultMarq26]

I think that everyone on the thread agrees to the same principle but is arguing different points.

Bel, you are saying that you can't add energy to the pole after take-off, yet, through muscle action, you can add energy to the system....I see what you are saying, but I don't think it is quite that black and white. If you are putting pressure through your arms with your lats or triceps, you will likely be adding some loading to the pole. I believe that is what everyone else is arguing.

So to answer the origional question, speaking strictly from science.....ENERGY is being produced from the muscles, but where is it going? Now you can get into the argument about reverse muscle actions.....does the lat muscle contraction put energy into the pole, or does it only pull the body into the correct position. Since the pole is bending, it must be having more energy put into it. On a rigid high bar, I would argue that, since the bar isn't moving, all muscle energy not lost to heat or sound, would have to stay within the body. Hense, Giants take a great deal of muscle strength and momentem (from muscle activation) to complete.