Self-siphoning beads
This is the coolest thing I’ve seen all day, and I’m pretty sure it’ll be the coolest thing you’d have seen all day, too: The Chain of Self-siphoning Beads, a.k.a. Physics Brainmelt.
It’s so simple; just think of the forces acting on the beads. Once a chain link is pulled up and let down, its kinetic and potential energies give it momentum going downward, and this pulls the rest of the chain up. The reason the loop doesn’t collapse is that it’s got some energy travelling along itself in the form of the beads’ momentum as they traverse that path. If the beads had been stationary, then the mass of the beads in the loop would’ve brought it down. Like a bicycle: A standing one would’ve toppled over; a moving one keeps moving.
