Can you add energy after takeoff?

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Can you add energy to the "vaulter-pole system" after takeoff?

No - you can't
7
16%
Yes - you can add energy during your swing - but not your extension
5
11%
Yes - you can add energy during your extension - but not your swing
0
No votes
Yes - you can add energy during your swing and during your extension
33
73%
 
Total votes: 45

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IAmTheWalrus
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Re: Can you add energy after takeoff?

Unread postby IAmTheWalrus » Thu May 14, 2009 10:30 am

From physics, the addition or removal of energy defines on the definition of the "system." One could say that NO energy is added because it is all present within the vaulter's body (as chemical potential energy I guess) at the start of the run, and is all contained (with the exception of inefficiencies in pole energy transfer) within the vaulter-pole system. Some of this energy is then translated to kinetic energy through the run and takeoff, and more of this energy is transferred to the pole during the swing and extension.

I believe this debate is entirely semantics. I believe most people, myself included, are looking at this in terms of the question "Does a vaulter's kinetic energy at takeoff determine his final height?" To that question, the answer is no, for the various reasons stated in previous posts. So I ask you, can we all agree that there is energy, beyond that of simply the run and takeoff, the aids in bending the pole and raising the vaulter's COM, and this energy comes from the swing and extension.
-Nick

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Re: Can you add energy after takeoff?

Unread postby KirkB » Thu May 14, 2009 11:26 am

Wally, that sums it up quite well. :yes:

But for me at least, this is not just semantics, and it's not just an academic exercise. It has a practical purpose ...

If you believe that your vault is predetermined at takeoff, then you will not see the value in perfecting your swing and your extension.

There is SO MUCH MORE that you can add to your vault after your takeoff, that this belief would hold you back from learning ... and perfecting ... your swing and your extension.

The only part of this discussion that's theoretical (nice to know, but can't do much about it) is the part about how chemical energy is stored in the muscles, and is used during the vault. That's nice to know, but!

The important part of this thread is to increase our understanding that once you leave the ground, you CAN and you SHOULD apply your MUSCLE-POWER to ADD ENERGY TO THE VAULTER-POLE SYSTEM in order to VAULT HIGHER!

Does the sum of the potential energy in the pole at takeoff (zero) and the kinetic energy of the vaulter at takeoff increase or decrease after he swings? Well, if he's inefficient and loses more energy than he gains, then it decreases. But if he swings his trail leg vigorously and transfers this additional kinetic energy (which came from chemical energy in the muscles, but who cares?) to potential energy in the pole, then at "full bend", the sum of the energy has INCREASED.

Likewise, as the pole recoils, potential energy is lost, and there's some loss of kinetic energy due to inefficiencies (any time you use your muscles, they heat up, dissipating energy). However, even while the potential energy of the pole is transforming back to kinetic energy (as you "ride the pole"), the SUM of the potential+kinetic energy can increase - due to a vigorous back-straightening extension.

Of course in the end, after all these energies have been applied (hopefully optimally), gravity will take over, stopping your upwards momentum, and pulling you back to earth.

In your final state, as you land in the pit, there is no more potential or kinetic energy left ... just as you started at the end of the runway.

True or not true? :dazed:

Kirk
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Re: Can you add energy after takeoff?

Unread postby VaultMarq26 » Thu May 14, 2009 12:10 pm

I'd say the last two posts explained the idea and answered the question perfectly. Marvelous!!!
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Re: Can you add energy after takeoff?

Unread postby vault3rb0y » Sat May 16, 2009 4:56 pm

Being someone who works with brad (bel) on a daily basis IRL, and knows that he likes technicalities and specificities, this debate has been truly comical for me. Thank you :).
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Re: Can you add energy after takeoff?

Unread postby H.I.S. » Sat May 16, 2009 9:21 pm

Explain this top me please, if the vault is predetermined after take off then how come

When I jump from 7 lefts and run at full speed and do not swing after take I do NOT penetrate into the pit nearly as deep from 3 lefts at a slow pace on the same hand grip but with a powerful swing?
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Re: Can you add energy after takeoff?

Unread postby bel142 » Sat May 16, 2009 10:21 pm

The reason is the results are not linear. There are so many variables in the vault that you change one, increase speed, but don't increase swing ability, or plant you are going to have detrimental results to you vault.

Very similar to Triple jump, athletes who have a great first phase but fall apart on the second and then can't pull out a third phase will have a short jump. An athlete who has an average 3 phase may jump farther.

When you hit the box faster you have to do things better, when you hit the box from 3 lefts things are slower and you can get away with allot more... But to say "well I am running faster why am i not jumping higher?" you are not looking at the vault as a whole... Hope that helps
-bel

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Re: Can you add energy after takeoff?

Unread postby KirkB » Sat May 16, 2009 11:00 pm

Sorry Bel, but I think you're throwing a red herring in here. What H.I.S. is trying to say (I think) is that "ALL ELSE BEING EQUAL, why can't I jump as well from 7 WITHOUT a vigorous swing as from 3 WITH a vigorous swing".

The vigorous swing is assumed to be the only variable ... it's ADDING ENERGY after takeoff!

It's a rhetorical question, with the answer being that you can in fact add energy after takeoff, and by doing so, you will vault higher.

Let's stay on topic!

Kirk
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Re: Can you add energy after takeoff?

Unread postby barragan » Fri Nov 13, 2009 3:31 pm

As a really quick aside in case anyone was wondering, jet propulsion works because of conservation of momentum. The change in momentum per change in time is due to external forces on a system. Therefore, if there are no external forces, momentum must be conserved (change of momentum is zero). So a jet's propulsion is not reliant on the medium it is moving in (air or space). It is due to ejecting mass at a high speed from the rocket. Momentum is mass times velocity. So if the rocket sends a bunch of mass (it's fuel) at a high speed in the opposite direction it wants to travel, it will travel at some speed in the opposite direction. Mrocket*Vrocket = Mfuel*Vfuel. While that is not a perfect analysis, it is the basic principle behind jets. Sit in a rolly chair that rolls on the ground really easily and kick your legs out rapidly. The chair should shift around a bit while you are moving. It must respond to your change of momentum. Of course, the friction in the wheels and the tiny friction from air resistance changes the results slightly, but it is the same principle. It's the same that Kirk mentioned happens when someone is in space and they try to move. All momentum conservation.

Just throwing it out there.

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Re: Can you add energy after takeoff?

Unread postby Tim McMichael » Fri Nov 13, 2009 3:51 pm

To me, the analogy of a gymnast on a high-bar puts this question to rest. An athlete hanging in a static position beneath their hands can propel themselves to a handstand. They have obviously created energy. This means that the swing can create energy above what is present in the velocity of the run alone. Energy takes the path of least resistance, so some of that force goes into the moving pole, thus adding penetration.

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Re: Can you add energy after takeoff?

Unread postby Capt Caveman » Fri Nov 13, 2009 6:08 pm

The energy was there the whole time, the athlete just used it. Now, can that same athlete produce more energy .... no they cannot, they are limited by how strong they are (all the human factors that are "the athlete"). There is a max limit to what the muscles can produce and that is why we train, to increase the amount of energy we can generate. The amount of energy in a vault has a maximum. It is stored in several different places, the athletes muscles, the pole, speed, technique, efficency. I would argue that you cannot add energy to a vault, you can use more of the energy (of which there is a maximum) available to you and use it in the most efficent way.
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Can you do things to raise your CoM after takeoff?

Unread postby KirkB » Fri Nov 13, 2009 7:07 pm

I thought my original question was quite clear ... [sigh]

Can your add energy after takeoff?

Perhaps I should have asked it differently.

What would be your answer if I said what I really meant, which is ...

Is your maximum CoM pre-determined once your takeoff toe leaves the ground, or can you do some actions post-takeoff to raise your CoM even higher?

Kirk
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Re: Can you add energy after takeoff?

Unread postby rainbowgirl28 » Fri Nov 13, 2009 7:48 pm

Does it matter?

You can believe that you are creating energy after takeoff, or you can believe that the max energy is already predetermined and you are just using more or less of it... but in the end, we all know that the more speed and better takeoff you have the better the potential is, and the better you behave after takeoff, the better you'll use that energy.

So in the end, you're trying to achieve the same thing. I mean even Bubka didn't maximize his potential on very many jumps. So whether he could have done things to create energy to jump higher, or whether he could have used the predetermined energy better, the end result is the same: he could have vaulted higher.
:confused:


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