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Posted:recently i was trying to findout the forces acting on my arms while doing my poi and after looking through 1000000000's of books i found the info, to my dismay i then found that the info was right here on the site.... aaarrrrhhhhhggg. but after getting bored with doing all the calculations on paper i got bored and decided that a computer can doo this soooooo mutch faster.anyway so i am writing a with my *tiny*!!! javascript knolodge a small script to work out the forces, speed and things involved in the basic physics of poi... and what i want to know is 1 when i have finished, malcom do you want a copy???, 2 cananyone think of anything else to put into it? and 3 it should be finished soooon so if you want to play i will put the address up shortly. oh and when it is up please feel free to change it and send it back, as i am always intrested in the diffrent ways that people put scripts together and it also means that the script will be improved... yay

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Malcolm
SAPPHIRE Member since Nov 2003

Malcolm

HOP admin
Location: New Zealand

Total posts: 1024
Posted:ajtag,I would love a copy.
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RegardsMalcolm


May your balls always burn

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Peregrine


member
Location: Mystic, Ct. USA

Total posts: 428
Posted:xestrel the physicist spent about 2 hours working on the proof of how poi works at Eastcoastspinfest...and why weight has nothing to do with speed...he somewhere lost a factor of 2 apparently, due to gravity but he claims that doesnt matter that much since astrophysicists are routinely off by factors of 3 or so...I'll see if he's written the thing up yet, it had quite nice illustrations ivolving vectors of force!
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and you guys can compare notes...Pere


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Posted:COOOOOOOOOOL!!! i want to see, i was talking to my physics teacher and he suggested to draw a insanely accurate, complicated vector diagram... but no me being thick decided not to and went for malcoms approach.... the simple way forgetting forces such as windspeed and gravity, 1: becouse i could not be bothered and 2: it would be quite hard for someone to work out the phisics of their own poi by just inserting 3 numbers into boxes. but i would love to see what that exstrel had written,!!!

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Pele
BRONZE Member since Dec 2000

Pele

the henna lady
Location: WNY, USA

Total posts: 6193
Posted:I remember that Pere! And at one point someone was helping him and I was listening and I got such a headache!!!!
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However, that little piece of paper was pretty impressive when all was said and done. I think we were looking for it right before everyone left and it couldn't be found.
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I'd be interested to see what came of that.I would like to then know from it how that would figure into wear and tear on my joints, though I imagine the fuel I use for breathing will get me long before any wear on my joints is evident!------------------Pele Higher, higher burning fire...making music like a choir...


Pele
Higher, higher burning fire...making music like a choir
"Oooh look! A pub!" -exclaimed after recovering from a stupid fall
"And for the decadence of art, nothing beats a roaring fire." -TMK

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NYC_not_PK


NYC_not_PK

One Tyred Guy
Location: Camaiore, Lu, Italy

Total posts: 203
Posted:As a physics guy myself, the physics of an object spinning on a string is very simple. Therefore, I'm not quite sure what you guys are trying to do. The simplest thing to do would be to get a spring balance and hook your poi up to it and actually READ the forces acting on it as you are spinning it! The only factors for centripital force are speed, mass, and radius. What other forces are you looking for?

PK is a god.. i love the Peeekster.

.:PK:. [poiinthepark founder member]


Educate your self in the Hazards of Fire Breathing smileSTAY SAFE! hug

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NYC_not_PK


NYC_not_PK

One Tyred Guy
Location: Camaiore, Lu, Italy

Total posts: 203
Posted:Just happened to be in my classroom during a break in the day and I hooked up my light glowstick poi to a force meter and found that they weigh about 50 grams or .5 newtons when just hanging. After spinning them I got the force meter up to about 7 newtons. This means that they had a force while spinning of 14 times that of when they were just hanging (or "14 Gs".) This means that when spinning ANY weight at that speed (normal poi speed) and length (normal poi lenght) ANYone should be feeling about 14 times the force of the same poi at rest. Granted, this is just a quick and inexact experiement with a very light poi set but I would expect it to be a rough guess at the outward forces. I'll probably do the math later to confirm it but if I don't finish grading these tests by 3rd period my kiddies will be grumpy.Centripital force = [(mass)(velocity)^2]/(radius)You can find the velocity by doingvelocity = (2*pi)(radius)/(time for one swing)Keep everything in meters, kg, and seconds. So one swing should take about 0.5 seconds if you're swinging at 120 beats/minute.Somebody want to check me on this?

PK is a god.. i love the Peeekster.

.:PK:. [poiinthepark founder member]


Educate your self in the Hazards of Fire Breathing smileSTAY SAFE! hug

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Posted:true true thats basicially what i worked out and i bet that you were spinning at about 1.8 r p s?the other forces i meant were when spinning the is air restance (especially with fire) and there is gravity.... ad probaly others... but i am not the super accurate kind. if you look in the articles place second from the bottom there is a topic on this, and all i can say is you had better mark those tests otherwise those kiddies will be on to you.anyway i will send this little script that i am working on to you....

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NYC_not_PK


NYC_not_PK

One Tyred Guy
Location: Camaiore, Lu, Italy

Total posts: 203
Posted:Did the math and got about 10g for swinging at 120 beats per second for a 65 cm poi. This means that every poi would "seem" 10x heavier when you are spinning it quickly. The only trick is that you don't measure the actual length, you measure the length to the center of gravity of the poi. And neglect air resistance. But, like I said, I did hook mine up to a forcemeter and got about 14g. Gravity gets insignificant as you are spinning faster... It only adds or subtracts 1g! I do think that this motion with this much force does suggest that one should take it easy on the wrists if you are using heavy poi. Repetitive motion on shoulders, elbows and wrists can't be good with a lot of weight. Take breaks and stretch out
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PK is a god.. i love the Peeekster.

.:PK:. [poiinthepark founder member]


Educate your self in the Hazards of Fire Breathing smileSTAY SAFE! hug

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Twist


member


Total posts: 160
Posted:I dunno... I've said it before and I'll say it again... I feel like spinning heavy poi for a long period of time really helps my repetitive stress crap.... my wrists and shoulders ache from the comp. all day... but spinning for an hour or so with weighted poi makes me feel a great deal better... and, when you think about it, many of the motions are not that repetitive, particularly if you are incorporating several different moves and rotational directions into your routine...

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