About the SA Blog Network

Amazing bead chain experiment in slow motion

The views expressed are those of the author and are not necessarily those of Scientific American.

Email   PrintPrint

Video of the Week #99, July 3rd, 2013:

From: Physics Week in Review: June 29, 2013 by Jennifer Ouellette at Cocktail Party Physics.

Source: io9

The BBC’s Steve Mould joins forces with Earth Unplugged to explore the strange behavior of of a 50-meter string of self-siphoning beads. No, they’re not magnetic. As Mould explains:
“Look at it as a sort of tug-of-war. You can see the outer chain is going to be travelling really quickly as it falls, which means the inner chain is going to be travelling really quickly, as well. And if you’ve got something traveling really quickly, it’s got momentum… So you’ve got the inner chain traveling up, but it wants to change so it’s traveling down, but it can’t do that in an instant, because that would require infinite force.
Instead what it does is it changes direction slowly over the course of a loop, so that’s why it almost has to be a loop, because it needs that time and it needs that space to change directions.”

Rights & Permissions

Comments 6 Comments

Add Comment
  1. 1. jtdwyer 3:01 pm 07/3/2013

    Wow – I guess these kids never had a Slinky!

    Link to this
  2. 2. silvrhairdevil 3:02 pm 07/3/2013

    Amazing as that is, I find it equally amazing that, in the 50 meters of jumbled chain, there were no knots or trapped loops.

    Link to this
  3. 3. scilo 7:08 pm 07/5/2013

    These beads? Other beads won’t do? We use to syphon gas in the good old fun days. I suppose if we go to solid fuel we can still have fun?
    Chain physics are not new. A rag hangin over the side of a bucket of water does the same, a bit less dramatic though.
    I wish he would have tried different methods of release, such as looping spiral before releasing the chain to the ground. He started with an arc and the chain found it’s own path. Would it repath if started with a fancier hand motion? A weighted starting piece? Liquid or gas in the beaker? I think it would find it’s way back to the original state, but who knows?

    Link to this
  4. 4. jtreml 1:22 am 07/7/2013

    I was really hoping you were going to show dropping the chain from a much greater height in the second experiment. Damn – I guess I have to get some chain!

    Link to this
  5. 5. jtreml 1:23 am 07/7/2013

    Oh, ps – great video guys.

    Link to this
  6. 6. 12:31 pm 07/8/2013

    Isn’t it happening because each bead is actually a little assymmetrical dumbbell, with the smaller end trapped inside the body of the large end, and able to swivel through a limited cone of movement? That restricted cone of movement is what creates the kinetic moment that causes the ‘chain’ to behave like that. I think each little dumbbell is trying to swivel outside that cone of movement, and when it can’t, it transfers its energy to the next dumbbell in the ‘chain’ and so on, and so on… ??

    Link to this

Add a Comment
You must sign in or register as a member to submit a comment.

More from Scientific American

Email this Article