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General Forums => The O' Club => Topic started by: Wayout on May 09, 2011, 06:59:37 AM

Title: Pendulum waves.
Post by: Wayout on May 09, 2011, 06:59:37 AM
The 'Math Guys' could probably explain this but I just think it looks cool. 

http://wimp.com/pendulumwaves/ (http://wimp.com/pendulumwaves/)
Title: Re: Pendulum waves.
Post by: ToeTag on May 09, 2011, 07:38:37 AM
I didn't look. Magnets would explain alot.



Put little orange dots on the middle of some larger balls and it would make a great target! 
Title: Re: Pendulum waves.
Post by: gyrene81 on May 09, 2011, 08:09:33 AM
it's more of a physics thing than it is a math thing although they go hand in hand... one of those  :headscratch: things...very cool looking though
Title: Re: Pendulum waves.
Post by: curry1 on May 09, 2011, 10:05:24 AM
That is very cool stuff not to mention trippy.
Title: Re: Pendulum waves.
Post by: 68ZooM on May 09, 2011, 11:01:50 AM
it really would of looked cool if he painted each ball with fluorescent paint and filmed it under intense black light
Title: Re: Pendulum waves.
Post by: dedalos on May 09, 2011, 11:16:59 AM
Explain what?  The balls are hanging at different lengths and therefore swing back an forth at different time intervals.  The rest is just a game your eyes are playing on you.  Your eyes retain an image for 1/8 of second I think so looking from that angle it looks like changing waves.  There is no advanced math or physics involved (unless the guy calculated the lengths of the strings to create that exact set optical illusions).  I have a feeling it would work as long as the lengths are different but it would produce a different sequence of waves.

Title: Re: Pendulum waves.
Post by: allaire on May 09, 2011, 02:58:58 PM
Ladies and gentlemen, Sir Buzz Killington.  That was cool but I have to agree with the fluorescent point and black lighting. :rock
Title: Re: Pendulum waves.
Post by: fbEagle on May 09, 2011, 03:27:24 PM
just ask mister Isac Newton he'll explain it lol
Title: Re: Pendulum waves.
Post by: Yossarian on May 09, 2011, 03:38:09 PM
Cba to think about it too much, but I'll say that the first part of dedalos' post is definitely right, but I'm not sure about the eye-trick bit.  I *think* it's probably the balls approximating simple harmonic motion, but that's as far as I've gotten ;)
Title: Re: Pendulum waves.
Post by: Pigslilspaz on May 09, 2011, 03:51:15 PM
Cba to think about it too much, but I'll say that the first part of dedalos' post is definitely right, but I'm not sure about the eye-trick bit.  I *think* it's probably the balls approximating simple harmonic motion, but that's as far as I've gotten ;)

Exactly, it's no eye trick. Just quick calculation of the string lengths to set up the effect. The curve caused by the balls while at rest has to be parabolic in order for the effect to work. I've made a couple myself, always fun to watch.
Title: Re: Pendulum waves.
Post by: dedalos on May 09, 2011, 04:24:41 PM
Exactly, it's no eye trick. Just quick calculation of the string lengths to set up the effect. The curve caused by the balls while at rest has to be parabolic in order for the effect to work. I've made a couple myself, always fun to watch.

Bah, give it a try.  If you pause the movie at the beginning you will she the curve is tinny almost a straight line.  I think you can get the effect as long as the lengths are increasing by the same amount.  The eye trick I was talking about was for the smoothness of the motion and the movement of the wave.
Title: Re: Pendulum waves.
Post by: bozon on May 09, 2011, 05:01:34 PM
There are two effects that can play here:
One is simple harmonics: if one pendulum has a swing period P and the other has 9/10P (for example), then after 9 swings of the first the other will complete 10 swings and they will be "in phase" again for a brief moment. Setting up the swing periods smartly, there will be several pendulums that can be in sync at any given moment. It is a game of common dividers (that's the english term?) of period fractions.

The other possible mechanism which will be much easier top set up is frequency coupling. If each pendulum can "shake" or swing a little the bar from which they hang, they can bring the other pendulums into sync. This will not be stable since there are many frequencies interacting at ounce and conflicting with the fundamental frequency of each pendulum. They will move in and out of sync naturally. It is similar to the effect above, only that the frequencies do not have to so precise. The bridge in guitars and other string instruments actually make use of such an effect (by passing vibrations between strings).
Title: Re: Pendulum waves.
Post by: ToeTag on May 10, 2011, 07:15:57 AM
was it just me? Or did it appear to slow down and then speed back up again.
Title: Re: Pendulum waves.
Post by: dedalos on May 10, 2011, 10:47:45 AM
was it just me? Or did it appear to slow down and then speed back up again.

Just your eyes
Title: Re: Pendulum waves.
Post by: Pigslilspaz on May 10, 2011, 01:54:07 PM
Bah, give it a try.  If you pause the movie at the beginning you will she the curve is tinny almost a straight line.  I think you can get the effect as long as the lengths are increasing by the same amount.  The eye trick I was talking about was for the smoothness of the motion and the movement of the wave.

The curve is small, yes, but it still follows a parabolic bath, just like the curve on a bullet is small yet it will still fall on a parabola. Also, it won't work if the length differences between two adjacent pendulums are same throughout. i don't know the formula off hand, but I will be willing to go and reread it and post it here about the relationship of pendulum length to it's period.
Title: Re: Pendulum waves.
Post by: bozon on May 11, 2011, 03:47:08 AM
like the square root of the length for an ideal (point mass on a massless string) pendulum
Title: Re: Pendulum waves.
Post by: Pigslilspaz on May 11, 2011, 03:56:14 AM
If only we lived in an ideal physics environment. Frictionless/massless objects at will  :D.
Title: Re: Pendulum waves.
Post by: dedalos on May 11, 2011, 08:47:35 AM
The curve is small, yes, but it still follows a parabolic bath, just like the curve on a bullet is small yet it will still fall on a parabola. Also, it won't work if the length differences between two adjacent pendulums are same throughout. i don't know the formula off hand, but I will be willing to go and reread it and post it here about the relationship of pendulum length to it's period.

Try it.  It should work although it will create different paterns
Title: Re: Pendulum waves.
Post by: kotrenin on May 11, 2011, 09:12:13 AM
This would be a fun one for any musically inclined types to watch.  Watching the different frequencies phase in and out of harmony with each other as their energy decreases made me think of watching guitar strings.  This is where the dots and the frets on a guitars fret board come into play, using natural harmonics to divide 1 string into to strings that play in harmony with each other.
Title: Re: Pendulum waves.
Post by: Pigslilspaz on May 11, 2011, 05:21:34 PM
Try it.  It should work although it will create different paterns

Might give it a try, but chances are that it will go into chaos quicker and take much longer to reach it's various harmonies.
Title: Re: Pendulum waves.
Post by: phatzo on May 11, 2011, 10:09:50 PM
All the balls are moving at the same speed, therefore the ones on the short strings have a shorter journey to their period than the ones on long strings. Think of two cars travelling 60mph on a round circuit, one has a one mile circuit while the other one has a mile and a half circuit.
Title: Re: Pendulum waves.
Post by: 4deck on May 12, 2011, 06:56:11 AM
Very Kewl.