16. The Vacuum Cannon!

Thomas, Robin and Patrick Kaplo discuss the amazing vacuum cannon and how it can be used to make physics thrilling. The cannon is now available in the shop. Buy it and you’ll be supporting the podcast while you have a BLAST!
It is half term next week in the UK so it will be two weeks until episode 17.

Timestamps

  • Mars rover named for Rosalind Franklin @ 00:47
  • Introducing the Vacuum Cannon @ 1:20
  • Robin and Thomas test the cannon @ 4:43
  • A joyful enterprise @ 11:40
  • Safety considerations @ 13:14
  • Tips and tricks for firing it @ 14:46
  • Ways to calculate speed @ 17:06
  • Selling the cannon @ 23:52

Summary

Patrick Kaplo joins the team to talk about the brilliant Vacuum Cannon. This is a recognised piece of equipment, although Thomas and Robin had not heard of it. Thomas built one and tested it with spectacular results. All schools should have one! The cannon is actually covered in detail by CLEAPSS and they give full instructions (with links to where to buy parts) on how to make one (CLEAPSS login needed).

Thomas was so keen to spread the joy, he decided to sell the cannon in our shop and you can pick one up for £20 (including P&P but you need to enter the code BOOM at checkout). You can also support the podcast by purchasing a small upgrade that includes a £5 donation.

Patrick Kaplo modelling the t-shirt
Patrick Kaplo rocks the tptp look.

Ways to teach… Distance, Speed and Acceleration

Episode 20 (assuming we make it) will be all about ways to teach distance, speed and acceleration (or displacement, velocity and acceleration). How do you do it and what works best for you?

Please share ideas or successes – or indeed questions – on our Facebook Page: https://fb.me/physicstp .  You can also message us via our website contact form at the.physicsteachingpodcast.com, Twitter @physicstp, email using  the address given in the podcast (if we remember) or by leaving a voice memo using WhatsApp or Telegram to the phone number in our Twitter profile, +44 7898 814716 (don’t call the number, nobody will answer, just hold down the microphone icon and speak your message). Don’t forget to tell us your name because we may use your audio in a future episode. Please do leave a voice memo: Thomas thinks nobody loves him.

The music we use remains One legged equilibrist polka by Circus Homunculus.

Patrick’s theme tune is from Hail to the Chief Bluegrass Banjo by Tom Adams from BanjoNews.com under Fair Use.

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Making a Vacuum Cannon

The Tube

The tube does not need to be super strong (the tape will fail long before the tube), but it does need to be close in diameter to a table-tennis ball (40mm). The right tube is known as Imperial 1½ inch PVC, common in the USA but not so much in the UK. I collected it from Koi Logic for £5.05 a metre since delivery is quite expensive and it is not too far away. CLEAPSS suggest the plastic pipe shop where it is about the same cost but you get a longer length (so more expensive and a lot of waste).

1m of tube is fine, it is easy to transport and store. You can get tremendous speeds from a 1m tube. CLEAPSS recommend that you do not go longer than 1.5m. I chose 1m because above that, the delivery charges get silly.

The valve and its Hole

You need a way to connect the vacuum pump to the tube. Patrick Kaplo sent me a link to the hose elbow he used in the USA and CLEAPSS suggests a metal schrader valve that you just self tap (force in to the PVC) and glue in to the pipe. Their instructions here are a bit vague on the size of drill bit you need. A very unscientific poll of physics teacher friends suggested that they all had rubber hoses on their vacuum pumps so the elbow is much more sensible.

Being a bit of a perfectionist I thought that tapping it in to a tapered thread would allow for cheaper components, a better seal and for replacing components if needed. I found some cheap nylon fittings at Wreking Pneumatics, all they needed was a correctly threaded hole.

For pneumatics I learned you really should used tapered thread (BSPT) holes to get a good seal with no need for tape, glue or sealant. Tracy tools are helpful on the phone and sell reasonably priced tap, dies and drills. I wasn’t sure what would work best so bought a plug tap and the correct size drill (8.4mm for the ⅛” plug tap) for both ¼” and ⅛” tapered thread holes. The prototype has ¼” BSPT but I learned that the schrader valves suggested by CLEAPSS and potential vacuum gauges all use ⅛” BSPT so the ¼” tap I bought was redundant. (I actually bought another but it took so long to come in the post via amazon I gave up on it; Tracy Tools delivered within 24 hours of ordering.) Tapping PVC is a doddle compared to steel.

The Tape

*just* an overlap

The tape was the cheapest “three inch” (78mm wide) tape I could find on eBay, just bought in bulk. The prototype used “two inch” and worked, but barely covered the width of the tube (see photo).

The Balls

The balls are practise balls from eBay, bought in bulk. “Real” balls are much stiffer and about twice the mass. I bought 300. Softer balls expand a little in the tube I think, so possibly get more push, and being lighter can accelerate faster? This is worth investigating perhaps?

No Flanges 😥

Flanges make a great stand for the cannon and provide a good surface for the tape to adhere too. The best I could find was £8 a flange, but that would almost double the cost of the cannon. Robin and I tested the cannon with no flanges with very good results. My tech department whipped two up for free with no problem and you can make basic ones out of cardboard or 3D print them. There are many options. Our tube’s diameter was 48mm (Officially 48.26mm according to the Standard). This is a good opportunity for the school to personalise their cannon!

Adding a Pressure Gauge

I found pressure gauges on eBay for £7 including postage. They come with a ⅛” BSPT (taper) male and screw straight in to another ⅛” tapped hole. Just search for:
1/8″ BSPT pressure gauge.

If you make one, do let us know how you get on:

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Selling a Vacuum Cannon

We are selling Vacuum Cannons in the shop. I am setting it up with some trepidation: if nobody buys one I will be several tens of pounds out of pocket. If everyone buys one I will be unable to make them fast enough to keep up with demand. Of course, the most likely thing is somewhere in-between. Being part-time I can respond quite fast, and I can limit the number I have to make and dispatch by setting the stock levels in our shop software. And through the piss-poor planning you have come to expect, we are releasing them a day before I go away for a week over half-term. Oops.

The pay-off is that more people will get to play demonstrate with this fantastic toy piece of equipment. I had never heard of it, nor had Robin, but CLEAPSS are all over it so it must be pretty well known. When I tested the prototype in the kitchen I didn’t really think through the consequences of a ball travelling at several hundred miles an hour vs my kitchen wall. There was ball debris everywhere; I found one shard 5m away on a high window sill two weeks later.

I have set up stock of 2 in the shop but with unlimited back orders. Once I know what the demand is (or indeed if there is any!) I will start making and shipping them in batches. I intend to keep doing them at £20 until I lose the will to go through all the guff of making, packing and dispatching them. Then I will either give up or raise the price. So buy now to avoid disappointment.

Anyone with access to a vacuum pump can of course make their own. If that is your plan, you could use the CLEAPSS guidance I mentioned above. I also made my own “How To” notes which includes links to where I purchased things.

If you make one, please let us know how it goes.

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15.1 Extended Interview with Nicky Thomas about Diffraction

Full interview with Nicky Thomas about teaching diffraction (29 minutes). She covers how she teaches it in more detail as well as more context and thoughts about doing diffraction as a practical EPQ.

The music in this extra episode is Cantina Rag by Jackson F. Smith. It was the runner up in our “Which music shall we have for the podcast?” play off.

15. Water, Waves and Woodlice

Sea slugs use physics to move up to 90 km a day. Who’d have known? In the main body of the podcast Robin talks to Nicky Thomas about teaching diffraction. She has much to share so we released an extended interview podcast Finally woodlice can also assist in physics teaching by being a source of real distance/time data.

Timestamps

  • Our secret plans @ 00:30
  • Plea for people to share their ideas about how to teach distance, speed and acceleration @ 1:54
  • Physics in the News: Sea Cucumber escape strategy @ 2:55
  • Nicky Thomas on Diffraction @ 5:09
  • Biologist Sylvia and using Woodlice to teach Physics @ 19:07

Summary

Robin and Thomas are excited about their secret plans for the weekend that are related to the future “Ways to teach…” episode on distance, speed and acceleration. Thomas then tells Robin about escapologist sea slugs that use their deep knowledge of physics to move up to 90km a day. The main guest this week is teacher Nicky Thomas. Her favourite thing to teach is diffraction and she describes how she tries to make it a progressive subject through the key stages. Nicky told Robin how she explores diffraction with different age groups and give some context for how it is used in industry by Panalytical. Thomas from the future appears to tell the listener that the interview had to be cut hard, but you can hear the whole half hour on a special bonus podcast that has been released The last part of the podcast is an idea linked to distance, speed and acceleration: using woodlice as a source of real distance time information. This is described by an old colleague of Thomas’, Sylvia Gummery.

Ways to teach… Distance, Speed and Acceleration

Episode 20 (assuming we make it) will be all about ways to teach distance, speed and acceleration (or displacement, velocity and acceleration). How do you do it and what works best for you?

Please share ideas or successes on our Facebook Page – https://fb.me/physicstp .  You can also message us via our website contact form at the.physicsteachingpodcast.com, Twitter @physicstp, email using  the address given in the podcast (if we remember) or by leaving a voice memo using WhatsApp or Telegram to the phone number in our Twitter profile, +44 7898 814716 (don’t call the number, nobody will answer, just hold down the microphone icon and speak your message). Don’t forget to tell us your name because we may use your audio in a future episode. Please do leave a voice memo: Thomas thinks nobody loves him.

The music we use remains One legged equilibrist polka by Circus Homunculus.

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BL4S Logo

14. Cataracts, Cameras and (CERN) Competitions

Thomas and Robin respond to a request from a listener and investigate the BL4S Competition run by CERN. Win an all expenses trip to a high energy beam lab where you will be supported to do your own experiment. They also announce the subject of the next “Ways to teach…” episode: Distance, Speed and Acceleration.

TimeStamps

  • Cataracts @ 00:58
  • Cameras that (don’t) see round corners @ 2:20
  • LSST and its huge camera @ 3:40
  • Beam Line for Schools (BL4S) Intro @ 5:12
  • BL4S @ 6:03
  • The next “Ways to teach…” Episode (Distance, speed and acceleration) @ 19:04

Summary

Robin describes a Camera that (doesn’t) see round corners. It was published in nature (PayWall) but The Guardian has a nice summary. The LSST 3,200 megapixel camera is being built in Chile (it turns out it is well under way, and not really news, but is still really impressive). The CERN Beam Line for Schools (BL4S) competition is the main focus this week in response to a tweet from @teachingofsci. Thomas chats with Prof. Pete Watkins and Dr Elizabeth Cunningham about the competition. The BL4S web site is a mine of useful information, including previous entry videos, previous winners’ 1,000 word proposals and ideas to get you started. Finally Robin introduces the next “Ways to teach…” Episode: Distance, Speed and Acceleration.

Ways to teach… Distance, Speed and Acceleration

Episode 20 (assuming we make it) will be all about ways to teach distance, speed and acceleration (or displacement, velocity and acceleration). How do you do it and what works best for you?

Please share ideas or successes on our Facebook Page – https://fb.me/physicstp .  You can also message us via our website contact form at the.physicsteachingpodcast.com, Twitter @physicstp, email using  the address given in the podcast (if we remember) or by leaving a voice memo using WhatsApp or Telegram to the phone number in our Twitter profile, +44 7898 814716 (don’t call the number, nobody will answer, just hold down the microphone icon and speak your message). Don’t forget to tell us your name because we may use your audio in a future episode. Please do leave a voice memo: Thomas thinks nobody loves him.

The music we use remains One legged equilibrist polka by Circus Homunculus.

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13. Lasers, Labs and a Large(r) hadron collider

Thomas and Robin had such fun talking to Patrick Kaplo (Episode 11) from Windham, New Hampshire that we talked to him again about his Challenge Labs. These are graded practicals where there is a one-shot event at the end of the practical that gives you your final grade. You can listen to how this works in an optics lab… err… practical in this episode or rewind to episode 11 for the sliced pendulum experiment.

Time Stamps

  • CERN Plans @ 00:20
  • Thomas uses Podcast ideas in his lesson @ @ 2:57
  • Challenge Practicals @ 6:48
  • Formative Feedback @ 9:53
  • Refractive Index based Challenge Lab @ 11:15
  • Post interview chat 19:40

Summary

Size isn’t everything, but no-one told CERN: they’ve announced designs for the next generation collider. Thomas and Robin are looking forward to find out just a little bit more about the Big Bang and the nature of matter. Thomas celebrated an inaugural ‘podcast day’ when in the same day he used the electric motors, mystery tubes and Perimeter Institute resources ( ‘Bubble Chamber Detective’) from previous episodes.

Friend of the Podcast Patrick Kaplow returns to be embarrassed by Robin’s hero-worship. Never has anyone been audibly grateful for thousands of miles of ocean. Patrick tells us about “Challenge Labs”, where there is a one shot answer that gives you your grade. He goes on to describe a simple refraction/reflection experiment to test students’ understanding where the grade is determined by a one shot attempt at predicting a laser beam’s path through a prism.

A brief caution: don’t forget to check with CLEAPSS (or your local Health and Safety body) that any Laser pens or cheap lasers are safe to use.

Please share ideas or successes on our Facebook Page – https://fb.me/physicstp .  You can also message us via our website contact form at the.physicsteachingpodcast.com, Twitter @physicstp, email using  the address given in the podcast (if we remember) or by leaving a voice memo using WhatsApp or Telegram to the phone number in our Twitter profile, +44 7898 814716 (don’t call the number, nobody will answer, just hold down the microphone icon and speak your message). Don’t forget to tell us your name because we may use your audio in a future episode. Please do leave a voice memo: Thomas thinks nobody loves him.

The music we use remains One legged equilibrist polka by Circus Homunculus.

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12. Shrink-Rays, Spectrum and String…

Thomas and Robin discuss why – when they are less likely than a podcast from the gym in January – media are still obsessed with Shrink Rays and mysterious (not Alien) Space signals. They soon move onto far more entertaining matters as they talk about teaching the EM Spectrum. Thomas tells us about his lovely “How long is a piece of String?” lesson. One of Robin’s favourites, it’s a great way of engaging reluctant students in the exploration of measurement, errors and uncertainty.

Time STamps

  • (not) Shrink Ray @ 2:50
  • Signals from Deep Space @ 4:50
  • Electromagnetic Spectrum @ 6:37
  • How Long is a piece of string? @ 14:18

Summary

It’s not a Shrink Ray: this is published in Science Magazine, but theengineer.co.uk is a bit more accessible. Remember to tell us your examples of how putting “Laser” on the front of everything makes the students think anything is better. Whys is any signal from space immediately attributed to Aliens? The BBC should know better. Helen CK’s question on Facebook about how to teach the Electromagnetic Spectrum finally gets addressed. (Sorry for the delay, Helen!) Your ideas will be bigger and better than ours so please share. Equally, if there’s something you want to throw open to the community, just let us know (twitter, contact form, instagram). If you find your students reluctant to engage with uncertainty and measurement, then you will love Thomas’s “how long is a piece of string?” practical.

The EM Spectrum

Helen CK contacted us long ago asking for ways to teach the e-m spectrum. Thomas and Robin chatted about how they would teach it. Thomas from the future visits to remind them that the Electromagnetic Spectrum song by Emerson Foo and Wong Yann is not to be missed (below). N.B. Take care with this song because there are some spurious ones set up in YouTube to fool and embarrass unwary teachers. Thomas mentioned “any number of Doppler effect videos on YouTube”, this is a good one.

Please share ideas or successes on our Facebook Page – https://fb.me/physicstp .  You can also message us via our website contact form at the.physicsteachingpodcast.com, Twitter @physicstp, email using  the address given in the podcast (if we remember) or by leaving a voice memo using WhatsApp or Telegram to the phone number in our Twitter profile, +44 7898 814716 (don’t call the number, nobody will answer, just hold down the microphone icon and speak your message). Don’t forget to tell us your name because we may use your audio in a future episode.

The music we use remains One legged equilibrist polka by Circus Homunculus.

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11. Poppers, Pendulums and Pond-hopping

The days are getting longer, and the monster Christmas term is behind us. Thomas and Robin refuse to let January blues dull the joy of physics teaching as they kick 2019 off with a cracker (pun intended). Two kinematic experiments are the focus, one using a pop-up toy and one that needs fire and blades.

Thomas and Robin also mourn those long-forgotten pieces of equipment buried in obscurity at the back of the cupboard. Please don’t leave them there to fester. If you have a piece of equipment you are unsure about, why not send us a photo by email or post about it in the forum, and do head that way if you want to talk about the episode, or anything else in Physics Teaching. 

Robin started the new year with a series of panic attacks after hearing about practicals that are both fun and difficult. The anxiety was only compounded by assertion that practicals can be graded, and don’t always evidence progress! He is currently recovering with the help of a Valium prescription and a copy of OFSTED’s annual report.

How great was it to hear from New Hampshire this week? Thanks so much to Patrick Kaplo from Windham High School for telling us about physic teaching in New England and giving us a practical in memoriam. Patrick joins our growing list of podcast heroes, not least because of this quote from the New Hampshire State Education Dept: ” Mr. Kaplo drives engagement in his classes by asking his students to build six foot tall trebuchets, ride CO2[sic]-powered fire extinguisher rocket carts… fire vacuum-powered ping-pong balls over 400 MPH, and visualize wave phenomena in an 8-foot long fire tube…”. As they might say in the States, we are totally getting him back again!

Robin has been trying to avoid cultural references that befuddle Thomas, but when he exclaimed “Jurassic Park!” he probably confused everyone. Anyway, this youtube video might help. For the record, Robin is much more like Alan Partridge than Thomas… in fact he’s more like Alan Partridge than Alan Partridge.

Success!

We start 2019 with the usual plea to share ideas or successes on our Facebook Page – https://fb.me/physicstp .  You can also message us via our website contact form at the.physicsteachingpodcast.com, Twitter @physicstp, email using  the address given in the podcast (if we remember) or by leaving a voice memo using WhatsApp or Telegram to the phone number in our Twitter profile, +44 7898 814716 (don’t call the number, nobody will answer, just hold down the microphone icon and speak your message). Don’t forget to tell us your name because we may use your audio in a future episode.

The music we use remains One legged equilibrist polka by Circus Homunculus.

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10. Ways to teach… Electricity

Merry Christmas Physics teachers!  In a bumper festive edition, Thomas and Robin have rounded up your ideas and tips on how to teach electricity.  It’s quite rare to reach a clear conclusion in a discussion of teaching, but there was consensus that if you are going to use a model, then the rope model is a great starting point, and Thomas has written a full description of a way to use the rope model in his blog.  We also acknowledged some other models and their usefulness: the important thing is to reflect and evaluate, but then again isn’t it always?

Resources

You can see all the tips and suggestions in a gallery at the bottom of the page.

We were delighted that the excellent PhET resources were mentioned by a couple of people. There are several electricity simulations, for example the DC construction kit.

Robin mentioned the Supporting Physics Teaching Web site, and its resources on electricity. It’s a great resource but is more akin to an Encyclopedia than a guide.   For a nice clear description of the rope model read the article by Tom Norris about teaching electricity. Tom also sent us a message after the interview:

Traditionally, in ks3 electricity schemes, you teach the electricity concepts, and *then* comes a lesson where you teach about electricity models. I personally wouldn’t do the “evaluating models” lesson unless I’m happy students’ understanding of electricity itself is at an expert enough level to be able to spot the subtle nuances of what the models do well and not so well. And also, secondly, because I don’t think knowledge of electricity models is anywhere near important enough to give a whole lesson to. The most important resource physics teachers have is time, and I the electricity topic I want to spend every lesson teaching about electricity itself. I don’t see electricity models as ‘content for students to learn’, rather, electricity models are something that I, the teacher, turn to, to help me explain/demonstrate the electricity concepts that I’m teaching.

Tom Norris

Lucky shot of an arc sparking

Thomas was delighted by the idea of driving a aluminium foil capacitor with the EHT. He duly did it and was delighted with the results.

What an exceptional community we are building!  All of this week’s podcast came from our growing listenership, so a million thanks.  Keep spreading the word, and if you liked the slightly different format (or not!), do let us know.  Similarly, if there’s anything you’d like to cover, please do share.  We plan another special on energy soon.

Have a good rest and we’ll see you in the New Year!

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