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Author Topic: Simulation of Track & Field event "Javelin"  (Read 22828 times)
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javcoach
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on: December 09, 2007, 08:24:49 am »

Hi,

I am a former coach of this event and would like to find a simulation that I can input speed of athlete "miles per hour/meters per second, and distance in inches/centimeters that it takes the athlete to completely stop.  I would like to find the force created by this simulation.

There are two varying techniques to this event.  The first one revolves around the ability to focus momentum as long as possible along the shaft of a javelin in much the same way as pulling back the arrow on the bow.

The second technique is just relax the body and stop your horizontal momentum as quickly as possible creating a reactionary force on the javelin.  The simulation would help to show young athletes the force they can create by stopping better.  There is a Car Crash example page that I use for the calculations but I would love to see a javelin flying in a simulation of this.  Here's the link for that car crash page.  http://hyperphysics.phy-astr.gsu.edu/hbase/carcr.html#cc1

Thank you for reading this.

Sean Elkinton
 
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Fu-Kwun Hwang
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Reply #1 on: December 09, 2007, 10:26:01 am »

I understand that if the athlete complete stop, all the energy can be pass to javelin to make it more effectively.

Could you upload some photos related to the event with your reply message?
So that I can know about the situation more clearly.
(Click additional Options) just below the message box, you will be able to upload files.
And provide me typical numbers: speed of athlete, initial speed of javelin (or distances )...
Can you give me some website which provides information related to your event?

The more information I can have, I should be able to create something better fit with what you want.
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javcoach
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Reply #2 on: December 09, 2007, 02:42:26 pm »

Thank you for your reply Fu-Kwun,

Here is a link to a series of animated photo's of the farthest throw ever thrown.  The throw was over 104 meters and an East German by the name of Uwe Hohn threw it.

http://www.geocities.com/jabalina_2y/UweHon104.80.gif

There is a very good paper written on the physics of javelin throwing located here:

http://www.leshatton.org/Documents/jav2007a_paper.pdf

The author states in it that "The javelin is not so much a throw as a long pull" this is his analysis but other techniques challenge
this statement.  The world record holder of the current javelin, Jan Zelezny, has a best toss of 98 meters.  He also has the shortest
pull of the current crop of throwers but he stops his momentum the best.  The number one factor of distance in the javelin is
speed of javelin at the release.  Jan has hit upwards of 33 meters per second in this factor.

The author of the web page also has a windows application for download that simulates many different factors on the javelin thrown
today and this javelin page and application can be found here:

http://www.leshatton.org/javelin_2005.html

There is a very clear and well graphed paper of the 11th World championships located here:

http://www.iaaf.org/newsfiles/38220.pdf

The simulation that I would like to see is how much force can be created on the javelin by stopping your momentum quickly.  In this
event, all throwers try to relax their arms and use the reaction to the stop as the main power for the javelin, if they anticipate the
stop and try to use their arm, it results in slowing the javelin down.  This may not sound correct for someone who has never thrown
but the arm just cant move faster then the reaction force on the javelin when a thrower stops.

Thank you agin Fu-Kwun for considering this simulation.

Sean Elkinton








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Fu-Kwun Hwang
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Reply #3 on: December 10, 2007, 11:31:47 pm »

Thank you for all the information provided, I will read them and layout a a draft for the simulation.
The gif image help a lot.

 I think I will try to create something similar to the above gif image.
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javcoach
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Reply #4 on: December 12, 2007, 10:11:51 am »

Your welcome and thank you too.  This is an event where you can't tell by
looking at a person if they are going to throw far or not.  Many times a big
strong fast person gets beat by a small weak slow person and it's one of the
reason I love coaching it.

Thanks again Fu-Kwun.

Sean Elkinton
« Last Edit: December 12, 2007, 11:09:10 am by javcoach » Logged
Fu-Kwun Hwang
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Reply #5 on: December 12, 2007, 09:58:23 pm »

From my point of view, the person who throw the javelin acting like a spring.
A stronger person is like a spring with larger spring constant.
But the force depend on spring constant (k) and the distance (dx) being compressed.
If you just move the whole spring very fast without compress it much, it might be beat by a slow moving spring with larger compression.
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javcoach
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Reply #6 on: December 13, 2007, 09:09:05 am »

I have been reading and posting a lot over the years on a few forums strictly dealing with javelin technique and let me tell you there are lots of different methods and techniques discussed.  I have always like to keep things real simple but others can discuss pages worth of information just dealing with the angle of the arm or neck compared with the the foot and ankle. Smiley

Here is how I see things regarding throwing the javelin very far.  It has to do with how sudden you stop.  That's it in a nut shell for me and I have had good success coaching throwers on how to stop.

A lot of coaches do see your type of mechanics in the throw and use a term called "elastic reflex" in discussing this spring effect.  Right or wrong I don't follow along with them because I see so much is missed when not discussing the huge reactionary force you can create immediately by stopping.

And let me now try to be convincing in discussing my rather absurd remark of how a little, slow, weak thrower can beat a big, fast, strong thrower.  If this sport relied on springs or the more common javelin coaching term called levers, throwers with longer levers, basically your big guys would win or throw father on average.  The fact is they don't.  I am not a physics major so please correct me when I get something wrong in that field but I believe it takes less force to stop something moving the same speed that is smaller in mass.  What I am trying to say is that little throwers stop quicker.

Second point is dealing with speed of the thrower but with the same principal in mind, the faster you go, the more force it takes to stop you.  So throwers that move faster, can't stop as easy as slower ones, resulting in loss of force they would get in a sudden stop reaction.

Third point strength.  I could go on and on with stories of javelin throwers setting records while in a weaken state, coming off illness, lack of sleep, etc.  I have discussed before the importance of relaxing you arm and not trying to time the throw.  If a thrower acts on a throw instead of reacts, normally the throw goes nowhere.  There are tons of big arm throwers that place last.  A lot of coaches picture the javelin throw like a whip type of action and a whip is quite thick and strong at the base but quite thin and weak on the opposite end.  If the end of the whip was the same as the base, I am sure the snap wouldn't be as loud or fast at the end.  Being weak in your throwing arm has big advantages in this event. 

So those are my points on my absurd statement.  Smiley

Now with the premise of being it's all about stopping, how do you do that efficiently?  How do you not lose your momentum before you stop?  A good majority of throwers lose a great deal of momentum on the second to last step.  When you notice Uwe throw above, take note of his right knee at the time he lands his right foot.  It is colasping.  It may look like a normal bend but he is moving at a good deal of speed, so keep that in mind.  If he didn't "soft step" that right leg, he would never get that plant leg down at a good angle to stop his moment and his momentum would be slowed before he is able to stop.  In the way I see things you want to carry as much speed as you can into the plant leg and if your plant knee doesn't buckle you going to create a huge amount of reactionary force.

Last thing is on the bend of the knee on the plant leg.  There are some very good coaches who think this isn't a big deal and some who suggest you should try to emulate a bend in the plant knee.  In my style of throwing/coaching, a millimeter bend in the knee is a horrible loss of a lot of reactionary force.  I think of this loss the opposite way seat belt manufactures think of making seat belts.  The design them so they slow you momentum down, real quickly of course but they definitely don't design them to stop you suddenly.  That would be way to much force on your body to take so they design a certain give to them.  In javelin throwing you don't want any give because you look to gain as much reactionary force which comes with this jolting sudden stop.

Thanks for reading my thoughts of this event Fu-Kwun.

Sean Elkinton
« Last Edit: December 13, 2007, 10:37:29 am by javcoach » Logged
javcoach
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Reply #7 on: December 17, 2007, 03:15:14 am »

I copied the Calculation of Force on Car page found here:

http://hyperphysics.phy-astr.gsu.edu/hbase/carcr.html#cc3

And changed it into something that make more sense to me as a javelin coach and put it up on my website.

http://www.throwinghuge.com/force.html


Sean Elkinton
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Fu-Kwun Hwang
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Reply #8 on: December 23, 2007, 09:19:05 pm »

I am sorry that I have not figure out a satisfied model to simulate your case yet.
I will keep in mind and I will let you know what I find out a good model to explain Javelin event.
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javcoach
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Reply #9 on: December 24, 2007, 07:28:22 am »

Thank you very much for keeping me informed.  There has been a big discussion lately on a javelin forum I post too about some new numbers coming from the last American championships.

I will link the thread below since several world class coaches and athletes have responded to it and it may give you another idea of how to explain the event through your model.

http://disc.yourwebapps.com/discussion.cgi?disc=109718;article=71575;title=%5BJavelin%20Discussion%20Forum%20II%5D

Thanks again Fu-Kwun,

Sean Elkinton
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aquixley
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Reply #10 on: October 10, 2008, 02:49:21 am » posted from:Farnham Royal,Slough,United Kingdom

Here's a link to a sequence of sixteen colour photos of Steve Backley, UK record holder, throwing the javelin. I think these would lend themselves to being animated as a gif file if anyone has the time and software to do it.

http://www.brianmac.co.uk/javelin/photo.htm
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Fu-Kwun Hwang
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Reply #11 on: October 10, 2008, 07:46:28 am »

Please check out the attachment. CLick the image to view animated gif.


* jav.gif (244.58 KB, 200x135 - viewed 459 times.)
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aquixley
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Reply #12 on: November 23, 2008, 04:50:50 am » posted from:Farnham Royal,Slough,United Kingdom

Fu-Kwun Hang, thank you for creating the animated gif.

I realise now that the static images I provided were not taken at equal time intervals, hence the rather jerky animation. It's a pity - my athlete would really benefit from a longer, richer sequence that we can slow down and study (which would probably require a hundred or more images in the sequence). The videos I find on YouTube tend to be very grainy and shot at too few 'frames per second' to really see the detail, especially at the moment of the strike. Does anyone out there know of a good quality slow-motion sequence of a world-class javelin thrower?
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Fu-Kwun Hwang
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Reply #13 on: November 23, 2008, 09:30:24 am »

There is a new camera CASIO EX-F1 which is able to take 300 shots per scecond with 512*384 resolution.
And it is not very expansive-- cost about US 1000.
I have used it to take several good quality dynamic motion quick time movies.
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imke24
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Reply #14 on: February 08, 2011, 09:09:19 pm » posted from:Singapore,,Singapore

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