The physics of that gravity-defying chain of metal beads

The physics of that gravity-defying chain of metal beads


I was totally baffled when I first saw that. It's so surprising that many sources covering this video assumed that the beads were actually magnets, presumably because that would make this strange phenomenon easier to swallow. But they aren't magnets - what you're seeing is just a boring old chain of metal beads, the kind that you might have at home hanging from blinds or from ceiling fans. (You can buy it here.) Which makes it even stranger.To get more news about ball chain curtain, you can visit mesh-fabrics official website.

So what's going on in this incredible video? How does a seemingly unremarkable chain of metal beads somehow appear to defy gravity? The physics nerd in me had to find out. Fortunately, there's an even more stunning slow-motion video where Steve offers us an explanation.

That's a nice explanation, but can we take it further. I'm in a particularly empirically zeal-ous mood, so in the spirit of this blog, let's do a calculation and work out if this explanation fits the data.

The first thing we need to know is what momentum is. Momentum is a measure of how much stuff an object has, and how fast that stuff is moving. Something that's fast and heavy has a lot of momentum. Something that's light and slow has very little momentum. Mathematically, momentum is just the product of an object's mass and its velocity.The second thing we need to know is that whenever an object changes its momentum, it experiences a force. If you think about it, this is pretty intuitive. For example, if you throw a tennis ball at a wall, its momentum changed from positive (forward) to negative (backward) when it bounces off the wall, because the wall slammed in to it (that's the force). If you were to slap the table in front of you, the momentum of your hand would go from something to nothing. The pain you'd feel is the direct result of the force that brought about this change in momentum.

Now, in this bead-chain, just as Steve described, the inner part of chain is traveling upwards, and then suddenly, at the top, its being pulled downwards. As each beads turn the bend, its change in momentum causes a little upwards kick of a force. There are many beads in the chain, and so there's a constant stream of little upward kicks, as the beads go around the bend. And it turns out that these kicks provide just enough of an upwards force to balance out the weight of the suspended part of the chain. That's why the chain seems to hover in mid-air - it's because the changing momentum of the chain provides a force that keeps it up.