Video of the Week #99, July 3rd, 2013:From:Physics Week in Review: June 29, 2013 by Jennifer Ouellette at Cocktail Party Physics.
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."