I’ve just started teaching circular motion to my Year 12s. There are some obvious demonstrations you can do when teaching this topic, such as spinning a bucket of water around your head, but I’m somewhat ashamed to admit that I’ve only just discovered the floating cork accelerometer which can be used to illustrate a key idea for this topic. Watch the video to see what I mean.
Massive thank you to my colleague Ronan McDonald for making the big accelerometer and volunteering to get dizzy.
[Edit 18/6/2013 – this post inspired a lively discussion at the Institute of Physics PTNC mailing list for physics teachers, which is a hidden gem of a community and a list every teacher of physics should at least be aware of. Sign up via the web interface. Thanks to everyone who cross-posted their comments here.
Joe Rowling had a nice blog post a few days before this, too – well worth a look if circular motion is your thing.
Science communication legend Ben Craven was in London over the weekend, giving me the chance to grab a quick bite with him while he waited for his train at King’s Cross. It also gave him time to show me a surprising demo related to his love of arches and for me to try out filming on my new iPhone 5. The picture quality is way better than my crappy old iPhone 3GS but the sound is problematic for doing something like this. Might need to invest in a lavalier mic of some sort…
[Oh, I see: requisitioning equipment via the blog. That’s your game, is it? Tsk. – Ed.]
This is a lovely demo shown to me by Andreas Tober, the Physics technician at Alleyn’s School in Dulwich, London (which also happens to be the secondary school I attended. I left shortly before Andreas started, but we’ve somehow managed to become friends anyway. Gotta love the internet). I think this is a lovely, simple way to introduce the idea of absorption spectra. I will definitely be using it in my physics teaching next year.
I would really like to take credit for “The Alom Shaha Motor” and “Alom Shaha’s jellybaby wave machine” because they’re two of my favorite demonstrations to use in class, but I can only wish that I had had the ingenuity to devise either of them. I’ve put my own spin on a few demos but the only thing I think I’ve invented from scratch was something to illustrate how the Mercator map projection works for an Adam Hart-Davis TV programme.
I’ve no idea who invented the simple electric motor demo, so that person is not credited in the film Jonathan and I made for our series of physics demonstration films for the National STEM Centre and IOP. But we do know who invented the jelly babywave machine… well, kind-of.
The first jellybaby wave machine was built for the Children’s ITV series The Big Bang, produced by Jonathan back in 2004. Whilst working at the Royal Institution years earlier, he’d seen a wave machine made of wood and metal. He’d wanted to recreate it in a way that children watching the show could build, and with his colleagues David Pitt and Luke Donnellan, came up with the now-famous jellybaby version. 150,000 or so young TV viewers would have seen it when that particular episode of The Big Bang was broadcast.
Surprisingly – perhaps because it was only shown on children’s TV in the days before YouTube – it didn’t become widely used by science teachers, even though it really is a fantastic way of introducing wave phenomena in the classroom. So Jonathan and I are delighted that the more recent film we made seems to have taken it into classrooms all over the world. Videos are a great way of sharing science demonstrations and it’s wonderful that the internet allows teachers and science communicators to find ones that are new to them, but I think it’s a bit of a shame that we rarely acknowledge the originators of these wonderful things we call demos. So, two questions to you, dear reader:
Can you name any classic demonstrations for which you know the inventor?
Funnily enough, only today Paul and I were discussing the importance of jeopardy in demos, and how the ‘best’ moments (particularly for children’s audiences) are often when things ‘go wrong.’ This isn’t quite what we had in mind.
What I don’t understand is why the bubbles are being lit on the ceiling. Typically, the methane bubble demo is done with a volunteer’s hands well wetted with the soap solution, and the bubbles lit on their hands. The perceived jeopardy is very much to the volunteer. It’s a lovely routine for building trust and establishing the purpose of exploring science (you get to do things to the world that are worth doing, and nobody dies). Setting up the demo in the way shown here is, I think, less impressive and less useful.
The imploding can demo is an old classic, often done with an old square-sided oil tin though I’m personally rather partial to the Coke can version. This, however, is something else. Commentary around the web suggests the method used here is to steam-clean the tank then seal the valves while it’s still full of steam. Which sounds plausible, and it’s not ridiculous to suspect this has been done as part of an industrial safety course.
Years ago I remember talking to David Jones about trying this – he’d long fancied having a go with a petrol tanker lorry. Even for TV the costs had looked prohibitive, and I never did find him an end-of-life tanker to play with. There’s also the minor issue of disposal to consider. But at least we can now be reasonably confident we could have made it work.
One concern, though: I’m not 100% convinced by the video. It’s from an interlaced source so it’s hard to tell for sure, but frame-by-framing the implosion makes it look to me like it’s been sped up somewhat. That said, the movement of the bogies looks appropriate. Ah, YouTube, you do so tease us with your ripped-off sources and your dodgy recompression.
I should probably run a ‘Wing Week’ here, but then I’d have to delve into explanations of how wings work. And we all know how messy that gets. So here’s a video from Ruesch Productions via the wonderful Fuck Yeah Fluid Dynamics, via @elinoroberts. I like demos on this scale, even if they’re more commonly known as ‘landing.’
As Pendulum Week continues here you’ll have noticed a pattern building up: that pendulums crop up in all sorts of demonstrations, but it’s often rather tricky to pin down satisfying explanations for their behaviour. Pendulums appear simple and straightforward to grasp, which is usually a good sign for demonstration tools as we want audiences to engage with ideas or behaviour and not be distracted by unfamiliar apparatus. However, I wonder if it’s possible that pendulums are too simple, in that their apparent simplicity seems to lull us into forgetting their subtleties.
Heck, unless you’re in that sin θ ≈ θ small-amplitude space you haven’t even, technically, got simple harmonic motion. Most of the time, pendulums don’t even swing like, well, pendulums. Ouch.
It feels like it ought to be possible to link pendulum demonstrations together in a neat story. A mass on the end of a string is about as simple as physics apparatus gets, surely there’s a delightful sequence of demos which can build successively, one on the other, to arrive at something complex and surprising and revealing about the world? That’s got to be possible, right?
Perhaps it is, but the origin of this series of posts lay in my noticing that pendulum demos aren’t alike, and the distinctions seem to me to be of the subtle-and-confusing kind rather than the subtle-but-illuminating kind.
Probably the best attempt I’ve seen to navigate the resulting swamp was by my colleague Marty Jopson, who made this film for the first series of Science Shack (skip to 2:40 for the start of the show):
Marty and I were co-producers on the series, and if I remember correctly he won awards for this show. I wasn’t, I should say, much involved with this episode (harrumph), but it’s still worth a watch. It gets into some of the subtleties about resonance and synchronisation that we’ve seen in this series of posts.