The Chain Fountain
Why Physics Stack Exchange recommends it
Physics Stack Exchange users link it as the standard demonstration of the chain fountain (self-siphoning beads) whenever they ask how to explain or model the effect.
Recommended by 0 people across 0 different months, 2015 to 2023.
What it is
A 36-second demonstration by Steve Mould of the chain fountain, where a bead chain in a pot siphons itself over the edge and rises in an arc above the pot as it falls to the floor. The description notes the beads are the kind used on office blinds and links to a slow-motion explanation.
Cited in 1 Wikipedia article, including Chain fountain.
What people said
Cites neverneve · 2015-02 · Physics Stack Exchange · on “Tension of a curled chain, connected with understanding the chain fountain”
I'd like to understand the physics of a chain fountain ( [this video] ) and in order to do so, I am reading this paper credited for solving the mystery: [LINK] Yet, I have trouble with the first equation, specifically $\frac{T_C}{r}=\frac{ \lambda v^2 }{r}$. Where does it come from? The right part seems like a representation for the centripetal force, but that's everything I am able to decipher.
Cites Deschele Schilder · 2017-01 · Physics Stack Exchange · on “Have the self sophining beads the same velocity when they reach the ground as the end velocity of freely falling beads?”
Look at this: [this video] The chain seems to be moving with a uniform velocity. Is the kinetic energy of all the moving beads in the whole chain (at the time they reach the ground) the same as the kinetic energy (when touching the ground) of the whole chain when you let it fall freely from the same height as the jar? Or move the beads in the chain with the velocity a single bead would have (when reaching the ground) as you let it fall from jar height? In both cases, the chain possesses the same potential energy.
Cites QuIcKmAtHs · 2018-01 · Physics Stack Exchange · on “The mystery behind the self-siphoning beads”
Recently, I saw this [this video] video, showing the phenomenon of the self-siphoning beads. Dangling one end of a coiled string of beads outside of the container, a single pull is needed to cause all the beads to fall out. Why is this so? My main question: It is also observed that the longer and more coiled the string of beads is, the higher the exiting beads will "jump". Why? This not only defies the principle of gravity that I learnt, but also the fact that energy cannot be created!
Cites Monopole · 2021-02 · Physics Stack Exchange · on “Euler-Lagrange equations for chain fountain”
Most of us are familiar with chain fountains. [this video] I was wondering how this phenomenon is explained in the Lagrangian mechanics. I mean do we know how the Euler-Lagrange equations look like for this system?
Cites mmesser314 · 2023-04 · Physics Stack Exchange · on “What is the reaction force when I "push" a string/rope/wire of some mass $M$?”
This question is confusing in part because of the way ropes are approximated in beginning physics classes. You connect masses together with massless strings. That way you can ignore the forces on them and focus on the forces on the masses. But what happens when you apply a force to just a massless string? You break the approximation. It is better to think of a chain for this kind of problem. Each link is a mass that transmits force to the next link. Unlike a string, the tension isn't always the same all through the chain. If you accelerate the chain, it is like accelerating a series of masses connected with strings. The tension in each string is different. You also think of a string as a thi