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Chain fountain

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Edited by Richard Walker, Tuesday, 23 Nov 2021, 12:37

Inspired by Steve Mould's videos about the chanin fountain, I bought 5 m of 3.2 mm beaded roller pull chain and took it down the pub, where it was a big hit.

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Here’s the explanation I sent my brother.

The favourite and probably correct theory goes like this.

Think of standing on tip-toe. If you stand on the floor and then pivot your ankles so your toes push against the floor then your toes exert a force on the floor and the floor pushes back with equal force. So this makes you move upwards. 

The beads of the chain are quite close and the whole assembly is not flexible in the way string is; there is a certain stiffness. As the chain unwinds from the container the segment currently unwinding acts a bit like your ankle; it rotates and pushes on the floor of the container and the floor pushes back. This imparts some upward momentum to the chain above, sufficient to make it fly up in the way seen.  But this explanation is controversial. It seems to be the case that string, being more flexible, behaves differently; we may get it to flow out but it doesn't rise up in the same way. So this suggests the theory may have something in it.