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Back of the Net!

When covering circular motion, I often find students a little resistant to the notion that at any particular moment in time, the direction of an object’s motion is at a tangent to the circle. They will of course nod and smile and agree with you when you say it to them, but if presented with specific ‘what-happens-next’ questions they often predict that a particle released from a circular path will spiral off in any one of a number of ways. So I was delighted when I saw somebody suggest a game like this one on twitter last year - though I can’t find them now to give kudos for the idea.

The game is simple. You have to get the ball into the goal. To do so you can speed it up as much as like by spinning it around inside the Sellotape roll before releasing it. And – crucially – when you release it, you have to do so by lifting the roll vertically off the table.

It’s surprisingly difficult even when you understand the idea and see the physics involved. And that allows us to play it over and over again, which helps to get the message across, and also have a bit of fun.

Of course, in anything set up as a competition, you’ll have a few inclined to push the boundaries of the rules, and in the first few runs of the game we came across a phenomenon that became known as ‘whooshing.’ This is when a player gives the ball a little shove in the right direction as they lift the roll, rather than trusting their ability to release it at exactly the right moment so that a tangential path will get the ball into the net.

But this only added to the merriment, as it allowed me to appoint ‘whooshing’ judges who position themselves just to the side of the table and kept an eagle eye on the direction of motion of the Sellotape roll as it is lifted. We even stretched the school’s phone policy a little bit so that we could have recordings and institute a VAR system of sorts. Although ultimately nothing can get in the way of an impassioned argument on a matter of little importance when it comes to sport. But that all adds to the entertainment in my view. And maybe even the educational aspects.

That is a Carom table I’m using here, by the way, which is a beautiful thing but not really essential to the game. Its just handy to stop the balls flying off the table. And it allows me to use the pockets instead of goals when a few students begin to find the game too easy. But you could also just make the distance to the goal a little longer.

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1 Comment

Noel Cunningham
Noel Cunningham
Apr 19, 2021

What a beautiful idea. Thanks David!

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