The Chain Fountain, Explained (?) <<Usually, physics research starts with a known problem. There are surprises, of course, but they don’t often come from Internet videos, as happened with the case of the mysterious chain fountain. It started with Steve Mould, a host of science television shows in Britain. Mr. Mould, who has a master’s degree in physics from Oxford, seems to be the discoverer of the chain fountain, which he demonstrated in a startling video posted online. In it, he pulls one end of a long chain of metal beads out of a glass container. Once he starts it off, the bead chain continues spilling out of the container on its own, like water or gasoline being siphoned from a tank. That, in itself, would be interesting enough. But the real surprise is that the chain doesn’t just run over the edge. It rises up in a curve, like a water fountain, as it falls....>>
more http://www.nytimes.com/2014/03/04/science/the-chain-fountain-explained.html Link to abstract http://rspa.royalsocietypublishing.org/content/470/2163/20130689 If a chain is initially at rest in a beaker at a height h1 above the ground, and the end of the chain is pulled over the rim of the beaker and down towards the ground and then released, the chain will spontaneously ‘flow’ out of the beaker under gravity. Furthermore, the beads do not simply drag over the edge of the beaker but form a fountain reaching a height h2 above it. We show that the formation of a fountain requires that the beads come into motion not only by being pulled upwards by the part of the chain immediately above the pile, but also by being pushed upwards by an anomalous reaction force from the pile of stationary chain. We propose possible origins for this force, argue that its magnitude will be proportional to the square of the chain velocity and predict and verify experimentally thath2∝h1. Harry
