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A simple wave machine made from tape, kebab sticks, and… jelly babies?
This film may be only a minute or so long, but there’s loads in it - slow-mo, fast-mo, stop-motion, time-lapse, animated captions, and artful angles. It was exhausting to make!
There’s a lot of subtlety to the wave machine too. The kebab sticks move the masses (jelly babies - fruit pastilles are good too!) away from the centre strip of gaffer tape. When they’re displaced up or down the tape twists, and there’s just enough torsional spring in it to bring the kebab sticks back to horizontal.
The result is a lovely slow wave rippling down the wave machine. If you watch carefully you’ll see that it reflects off the end, too.
Have a go at making one! A couple of tips: the kebab sticks have to be balanced horizontally, which is why not all the jelly babies are right at the ends of the sticks. Also, don’t try to make too long a span, or spread the kebab sticks too far apart. This group got it about right, we reckon.
You can buy wave machines from educational suppliers, but this design is almost as good and costs about a hundredth as much!
It was developed by Luke Donellan, a brilliant researcher who worked with me on CITV’s The Big Bang (fans of the series might recognise several of the demonstrations here at SciCast - hey, what’s a little recycling between friends?). Luke’s design is elegantly simple - just a strip of tape used as a torsional spring, and a bunch of masses (jelly babies) on the end of sticks (kebab skewers).
Just about everything you can do with a ‘real’ wave machine, you can do with this. Compare wave speed for different amplitudes? Check. Observe wave packet dispersion? Check. Eat the machine afterwards? Ah, on that point we win hands-down.
[update: we made a film describing how to make the wave machine in more detail, and exploring some of the physics you can show with it, for the Institute of Physics and the National STEM Centre. You can view the film here, and explore the set of physics demo films we made.]