Pendulum Waves

Fifteen uncoupled simple pendulums of monotonically increasing lengths dance together to produce visual traveling waves, standing waves, beating, and (seemingly) random motion.

For more details see http://sciencedemonstrations.fas.harv...

The period of one complete cycle of the dance is 60 seconds. The length of the longest pendulum has been adjusted so that it executes 51 oscillations in this 60 second period. The length of each successive shorter pendulum is carefully adjusted so that it executes one additional oscillation in this period. Thus, the 15th pendulum (shortest) undergoes 65 oscillations.

Our apparatus was built from a design published by Richard Berg [Am J Phys 59(2), 186-187 (1991)] at the University of Maryland. The particular apparatus shown here was built by our own Nils Sorensen.

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Video courtesy of Harvard Natural Sciences Lecture Demonstrations, © 2010 President and Fellows of Harvard College

• Category

  Education

[Nate Guy]

This comment disturbs me. Not by the fact it's insulting; however, about 80 people agreed and promoted this. I have not taken Physics. And my "basic" understanding comes form programming some basic Physics simulations. Like friction, velocity, and gravity. I just learned about atmospheric pressure a week ago from Chem H; and made me think of this video. Now, I find people of science insulting me, rather then helping me. It's an insult not to me. But to science, the act of sharing knowledge.

[AwesomePossumVids]

Not completely. If he/she has only taken basic physics, all they've learned about it objects in systems without friction. So from his/her current perception, they're right.. It would go on forever.. In a Physics 1 world.

[Rubethebest]

That other chap was a prat - ignore him! You're right to ask!! Unfortunately nothing will continue moving forever if it is moving through anything other than empty space.

[monted91]

welcome to the internet, guy.

[FlamingEnigma]

No because of friction.

[basel daradkah]

like you know who he is, he could be a 10 year old

if you were be a 10 year old you will be asking that

[TheFunkyGames]

it will just continue to swing forever, or is there some point where it stops moving?

[Calvin Le]

Makes you think twice about vibration and music strings in regards to all things set in motion.

[AwesomePossumVids]

Wind resistance can be looked at like friction. Also, you only look at linear friction. These pendulums experience rotational friction. It's a very different problem

[Danielle Holzberger]

Yeah, I'm in high school taking physics right now. It's not that we neglect friction, we actually did a whole unit on friction. What we neglect in all problems is wind resistance.

[AwesomePossumVids]

That's exactly what I said. If you live in a Physics 1 world, you might not be dealing with those small forces (friction, wind resistance, which is also friction). Don't talk to me like you're correcting me when you're just saying the exact same thing in a less intelligent way.

[dfarmbrough]

If you ignore the fact that the thing slows down to the point that it will eventually stop or be disturbed by some very tiny external force, the progression would go on forever.