So would two pendulums of the same length hung from the same string (like on the Wikipedia page) be considered in phase, even though they have opposite patterns? What about the Wilberforce pendulum? Is it considered to be in phase?>> ^crotchflame:

You're right: a double pendulum is a coupled oscillator and is a good example. It's a coupled oscillator with multiple normal modes that can give it a complex motion even for small oscillations where it isn't chaotic - some would argue that at larger amplitudes it's no longer a simple oscillator so a lot of the terminology in use here doesn't apply. The point is that it doesn't settle into one coupled mode that is stable against perturbations the way phase locked oscillators would.

>> ^messenger:

I'd imagine very few of them phase lock, no? Most of them result in chaos, I'd think, assuming a double pendulum counts as coupled oscillation.>> ^crotchflame:
>> ^draak13:
Actually, the answer is known as coupled oscillation
http://en.wikipedia.org/wiki/Oscillation#Coupled_oscillations

Oscillators have to be coupled to phase lock but not every coupled oscillator phase locks.




You're right: a double pendulum is a coupled oscillator and is a good example. It's a coupled oscillator with multiple normal modes that can give it a complex motion even for small oscillations where it isn't chaotic - some would argue that at larger amplitudes it's no longer a simple oscillator so a lot of the terminology in use here doesn't apply. The point is that it doesn't settle into one coupled mode that is stable against perturbations the way phase locked oscillators would.

I'd imagine very few of them phase lock, no? Most of them result in chaos, I'd think, assuming a double pendulum counts as coupled oscillation.>> ^crotchflame:

>> ^draak13:
Actually, the answer is known as coupled oscillation
http://en.wikipedia.org/wiki/Oscillation#Coupled_oscillations

Oscillators have to be coupled to phase lock but not every coupled oscillator phase locks.

@Kalle: Another machine that runs on gravity is an old-fashioned cuckoo clock. It uses a pendulum, yes, but that is to keep time. The energy comes from hanging weights which fall slowly (very slowly) as they deliver energy into the machine (mostly to overcome friction). When the weights reach the floor, somebody needs to come and pull them back up again, thus adding more (potential) energy to the system.

This guy has created an interesting sculpture, but it is not perpetual motion. He is certainly cheating--perhaps with weights hidden inside the central column; hopefully not with a hidden electric motor. He might know that he is cheating or he might just be fooling himself as a result of his stated ignorance of physics.

>> ^Kalle:

One serious question that bothers me is.. why isnt it possible to use gravity as an energy source?
Would such a machine be a perpetual motion machine?

There is a bottom to a gravity well (apart from Black Holes? I don't know ). Say you drop an object and harvest some of its kinetic energy as it falls...what do you do once it reaches the bottom of the well? You must exert energy to pull it back out of the well, and that energy is greater than what you gained from dropping it. In a sense a pendulum makes this transaction with every swing. It does it very efficiently, only losing a fraction of its energy with each exchange but none the less it does lose energy. In a sense we never truly generate energy, we simply move it around. We break chemical bonds and withdraw a portion of the energy that was needed to make those bonds. Whenever we put an object with any mass on a high shelf we use some our energy and give it potential energy. Should it fall from the shelf this potential is converted to kinetic. The most plentiful supply of locked away energy? Probably mass. The speed of light squared is a big number, as GeesussFreek says, the future is probably fusion. If we can convert just a tiny fraction of this planets mass to energy cheaply and safely then our energy problems are more or less solved.

Anyway, I hope that somewhat answered your question. Its one of those questions that on the face of it seems simply to answer but once I tried I realised it wasn't so easy

To me this object looks like an extremely efficient pendulum. I actually love its design. The fact the ball "orbits" is actually very apt. I don't think its perpetual motion, but if it really had been going at near constant speed for that long then it is still a very impressive piece of engineering. He should patent and start making more. I'd bet people would pay a pretty sum for a scaled down version sitting on their desk. I would. Even better, put a lightbulb in the centre, surround it with 8 concentric rings for each planet and tweak the weights/magnets so the balls orbit at approximately the right speed...that would be fucking sweet.

>> ^Fantomas:

Did you know that there's a direct correlation between the decline of Spirograph and the rise in gang activity? Think about it.


Always thought I was the only one that recognized the relationship...should be obvious to anyone who can draw a perfect circle simultaneously with both hands behind their back on a chalkboard!!?

>> ^hpqp:

Now that's some awesome father-son activity. I believe it involves some engineering as well.
And a good illustration of how it's the time you spend together that's important more than what's ultimately accomplished.

Your video, Rembember the Spirograph? Three Pendulum Rotary Harmonograph, has made it into the Top 15 New Videos listing. Congratulations on your achievement. For your contribution you have been awarded 1 Power Point.

That pendulum experiment is very cool. I think a lot of adults would be apprehensive about that, even though that can simply can't hit your face as long as you don't apply any push to it.

Government created the "super Pac". The only reason the Republicans are getting super pac money is because the democrats are screwing the county badly.

The pendulum will swing back some day after the Republicans gain control and start screwing up.

So Bill quit bellyaching. Your team will be back on top some day.

8 more comments have been lost in the ether at this killed duplicate.

This video has been seconded as a duplicate; transferring votes to the original video and killing this dupe - dupeof seconded with isdupe by deathcow.

*dupeof=http://videosift.com/video/Wave-Pendulum

This video has been nominated as a duplicate of this video by garmachi. If this nomination is seconded with *isdupe, the video will be killed and its votes transferred to the original.

I disagree, the audio on the other one is stupid I'm not calling it, mainly because I'm too lazy to look up if audio is enough of a difference, but if someone else wants to look it up and invoke...>> ^Zawash:

Naw - even though I don't have permissions to invoke it, it's a dupeof=http://videosift.com/video/Wave-Pendulum
Or this one - with music.