Hi everyone,
I am a hooper, and I like to know what the physical forces are behind what I do, to aid in instruction. A question I have been asked by a fellow hooper is why when doing the move shown in the link below, the hooper can turn only in the same direction in the hoop. The move will not work if you try to turn in the opposite direction. Here is the move being discussed:
www.christagiles.com/video/orbit.wmv (requires Windows Media Player)
Also, if this sort of stuff interests you, here is a little video tutorial of mine on the physics of hooping and other flow toys. I would love to hear any thoughts more educated people have on this matter:
www.youtube.com/watch
I am a hooper, and I like to know what the physical forces are behind what I do, to aid in instruction. A question I have been asked by a fellow hooper is why when doing the move shown in the link below, the hooper can turn only in the same direction in the hoop. The move will not work if you try to turn in the opposite direction. Here is the move being discussed:
www.christagiles.com/video/orbit.wmv (requires Windows Media Player)
Also, if this sort of stuff interests you, here is a little video tutorial of mine on the physics of hooping and other flow toys. I would love to hear any thoughts more educated people have on this matter:
www.youtube.com/watch
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Ohio
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Re: Question- Physical forces of a hooping move
Mon, March 12, 2007 - 11:45 PM1) you've got a great perspective on physics. i would bet that you'd have the tools to understand a fair amount of advanced physics because you seem to think clearly and carefully. (i glean that perspective from your youtube video).
2) i'd like a little more clarification about your question, because I don't quite understand it. you ask:
"why [can] the hooper ... turn only in the same direction in the hoop?"
The reason i don't quite understand you question is because of what happened to that sentence around the word "in". :-)
Would it be fair to restate your question the following way? I'm a little unsure of this restating because I'm not even sure that what I say below is true...
A) A hooper can spin a hoop counterclockwise (from their own perspective) around an axis that goes through its circumference if they themselves are moving counterclockwise as seen from above.
Given statement A) why, when they themselves are moving clockwise (as seen from above) must the reverse the direction of rotation of the hoop from their perspective?
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Lemme try again... for this move.... why must the rotation sense of the hoop from the hoopers perspective (CW or CCW) match that of the hooper as seen from above?
First off I think the answer to you question will turn out to be rather complex. But before I think too hard about it (because I'm sure there's some good thinking to do here, smoke coming out of the ears kind of thinking) I'd like to know if I have the question correct. =)
regards
Christian Nally
Galiano Island, British Columbia
www.sticksallison.com
p.s. my guess (if indeed i do have the question correct) is that it has something to do with the following... you must have at least one part of your force upward on the hoop to counteract gravity, and looking at your hoop as a gyroscope (for that indeed is what it is ;-), a gyroscope that is spinning in a given direction will itself tend to rotate around its support point in a determined sense. that determined sense must match the sense of motion of the hooper.
so... a little experiment to do here... get a gyroscope (the kind you set spinning by pulling a string that's been wrapped around its axis while holding the outer frame?) and set its axis on a pencil tip. you'll have to think clearly about the angular momentum of the hoop in this situation compared with the gyroscope.
anyway... my statements so far are less of an explanation, than they are to say 'look... here's another system that does the same thing'. the deeper understanding to your question will come when you understand how torque effects angular momentum. the math behind that can be fairly complex, but playing with a gyroscope will build some intuition. -
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Re: Question- Physical forces of a hooping move
Tue, March 13, 2007 - 3:57 AMThanks!
Yes, my question should have read: " Why can the hooper turn only in the same direction AS the hoop." You restated it well.
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Re: Question- Physical forces of a hooping move
Fri, March 16, 2007 - 2:02 PMSo for the hooping move, might it be the force called "precession?"
Here is a simulation of gyroscopic precession: www.youtube.com/watch
Would the fact that the hoop does not have the inner part of a gyroscope negate gyroscopic forces?
Bueller?....
Bueller?...
Anyone? -
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Re: Question- Physical forces of a hooping move
Fri, March 16, 2007 - 2:53 PMI believe Christian had at least part of the answer. In working out the angular momenta and torques, I didn't come up with anything other than precession due to gravity.
Precession is not a force, it's a description of the type of motion.
The fact that the hoop has an empty interior makes no difference. It will still have angular momentum as it spins.
Changes in angular momentum are produced by torque. Torque has a mathematical definition that I won't get in to. You can think of angular momentum and torque as being analogous to regular momentum and force. However, the results can be a little counterintuitive.
In the hoop case, taken from the perspective of the hooper, the angular momentum vector would point either away from the hooper (clockwise rotation by standard definitions) or toward the hooper (counterclockwise rotation). The torque due to gravity will always point to the hoopers left. So that is the direction of change of the angular momentum vector. In the CW case, this means the hoop tries to rotate (precess) in a CCW direction (as viewed looking down at the hooper), so that flows naturally with the hooper's CCW rotation. In the CCW case, the hoop tries to precess in a CW direction, counter to the CCW motion of the hooper.
I wouldn't think this would make the move impossible, just more difficult. Can you describe what happens when you try it?
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Re: Question- Physical forces of a hooping move
Tue, March 13, 2007 - 11:28 AMOn a related note:
Is there a physical reason why antispin poi moves are so much harder. "Antispin" is anything where the point of rotation of the poi is move in a circle in the opposite direction as the poi themselves.
For example, here is a flower: www.homeofpoi.com/lessons_a...ch/3_18_67
and here is the same move in Antispin: www.homeofpoi.com/lessons_a...ch/3_18_69
You can also see both variations in this short little vid of me, starting at about the 30 second mark: www.youtube.com/watch
Also, it is much harder to keep good planes on a horizontal buzzsaw, if you are turning your body against the poi. Even if you are turning slowly. The move is not hard if you are turning the same direction as the poi.
A horizontal buzzsaw is this move done on its side: www.homeofpoi.com/lessons_a...ach/3_8_72
Thoughts? -
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Re: Question- Physical forces of a hooping move
Fri, March 16, 2007 - 2:58 PMIf you think of the direction of tension you must apply to the poi to cause it to rotate, you can see that in the regular spin direction, the wrist would, in effect, move around in sync with the direction the arm is moving. In antispin, the wrist/hand would have to trace out a circle in a direction counter to the circle the arm is tracing. Seems like that would take more coordination. Possibly more than I have... ;-)
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