Date: Fri, 15 Oct 2004 16:50:59 -0500

Author: A Gavrin

Subject: Re: localized energy mode demo, i.e pendulum revisited

Post:

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Here's a possible wrinkle. If the pendula can go all the way over, you
can end up with a full twist stored in the spring between two pendula
that "look" parallel. This would be a "kink" type solution similar to
those observed in some systems that have soliton solutions, e.g., the
"sine-gordon" equation.

Did they show that, Sam?

- Andy



sampere wrote:

> And a followup, this effect wasn't discovered until the late '80s, so
> it's relatively new.
>
> Sam
>
> Richard Berg wrote:
>
>>For small amplitudes, they might end up all moving back and forth together
>>in phase.
>>
>>For large amplitudes, they might end up moving back and forth with
>>adjacent pendula out of phase.
>>
>>But then again, they might not.
>>
>>DB
>>
>>On Fri, 15 Oct 2004, sampere wrote:
>>
>>
>>
>>>I saw the coolest demo yesterday. Al Sievers from Cornell gave a
>>>colloquium here yesterday and brought a demo with him.
>>>
>>>Picture a dozen small identical pendulms suspended from a single rod,
>>>perhaps from a bearing, so the rod does not play any role in
>>>transferring energy. Then, connect each of the pivot points with
>>>springs so that as the pendulums oscillate, the springs either wind up
>>>or unwind. The direction of oscillation is perpendicular to the length
>>>of the suspension rod, i.e., if the pendulums all dangle from rod
>>>horizontal and parallel to your screen, the pendulums oscillate in and
>>>out of the screen.
>>>
>>>So, here are two questions for you:
>>>
>>>1) For small starting amplitudes, the initial conditions for all pendula
>>>being equal, what do expect to see?
>>>2) Same as 1, but for very large starting amplitudes?
>>>
>>>I'll post the answer later after I hear your thoughts.
>>>
>>>Sam
>>>
>>>
>>>
>>>
>>
>>***********************************************************************
>>Dr. Richard E. Berg, Professor of the Practice
>>Director, Physics Lecture-Demonstration Facility
>>U.S. mail address:
>>Department of Physics
>>University of Maryland
>>College Park, MD 20742-4111
>>Phone: (301) 405-5994
>>FAX: (301) 314-9525
>>e-mail reberg@physics.umd.edu
>>www.physics.umd.edu/lecdem
>>***********************************************************************
>>
>>

--
Dr. Andrew D. Gavrin
Department of Physics, 402 N. Blackford St.
Indiana Univ.-Purdue Univ. Indianapolis
Indianapolis, IN 46202-3273

317-274-6909 (Ph) -2393 (FAX)
agavrin@iupui.edu


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Here's a possible wrinkle. If the pendula can go all the way over, you
can end up with a full twist stored in the spring between two pendula
that "look" parallel. This would be a "kink" type solution similar to
those observed in some systems that have soliton solutions, e.g., the
"sine-gordon" equation.



Did they show that, Sam?



- Andy







sampere wrote:




And a followup, this effect wasn't discovered until the late '80s, so
it's relatively new.



Sam



Richard Berg wrote:

cite="midPine.OSF.4.44.0410151217540.370-100000@student1.physics.umd.edu">
For small amplitudes, they might end up all moving back and forth together
in phase.

For large amplitudes, they might end up moving back and forth with
adjacent pendula out of phase.

But then again, they might not.

DB

On Fri, 15 Oct 2004, sampere wrote:



I saw the coolest demo yesterday.  Al Sievers from Cornell gave a
colloquium here yesterday and brought a demo with him.

Picture a dozen small identical pendulms suspended from a single rod,
perhaps from a bearing, so the rod does not play any role in
transferring energy. Then, connect each of the pivot points with
springs so that as the pendulums oscillate, the springs either wind up
or unwind. The direction of oscillation is perpendicular to the length
of the suspension rod, i.e., if the pendulums all dangle from rod
horizontal and parallel to your screen, the pendulums oscillate in and
out of the screen.

So, here are two questions for you:

1) For small starting amplitudes, the initial conditions for all pendula
being equal, what do expect to see?
2) Same as 1, but for very large starting amplitudes?

I'll post the answer later after I hear your thoughts.

Sam





***********************************************************************
Dr. Richard E. Berg, Professor of the Practice
Director, Physics Lecture-Demonstration Facility
U.S. mail address:
Department of Physics
University of Maryland
College Park, MD 20742-4111
Phone: (301) 405-5994
FAX: (301) 314-9525
e-mail href="mailto:reberg@physics.umd.edu">reberg@physics.umd.edu
href="http://www.physics.umd.edu/lecdem">www.physics.umd.edu/lecdem
***********************************************************************





-- 
Dr. Andrew D. Gavrin
Department of Physics, 402 N. Blackford St.
Indiana Univ.-Purdue Univ. Indianapolis
Indianapolis, IN 46202-3273

317-274-6909 (Ph) -2393 (FAX)
agavrin@iupui.edu




--------------080109050700060909030105--
From sampere@physics.syr.edu Sun Oct 17 20:37:45 2004

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