The Young Modulus – Instructions

This is a way to determine the Young Modulus as an individual, rather than group practical. For years I thought that you needed a pulley for the wire, but it turns out you don’t. Without that limiting factor, it becomes a pfaff reducing exercise.

Summary

Get a plank of “whatever you can find” width, about 1.2m long, drive a screw in about 5cm from one end. Photocopy a normal ruler at 100% then at 90%. Check the reduction is accurate! Use the 90% to make a vernier scale. Get about 2m of 32swg copper wire and tape the vernier scale to the wire at 1m from the nail. Line the vernier up with the 100% scale and gently hang 1N weights to the end of the wire that hangs off the end of the plank, measuring each extension. The diameter of the wire is done traditionally by using a micrometer or looking up the diameter of swg wire in mm.

Steps and Photos

This is one of our dynamics ramps, but any old plank could be used. It needs to be more than 1m long and should stick out over the desk to give the weights room to hang. This is 32swg copper wire, diameter 0.27mm
90% photocopy of the ruler. Do check that 10.0cm in the copy is 9.0cm on the real ruler (some photocopiers reduce by a few percent as a matter of course). It may take some trial and error (keep notes for next time…). In the experiment I took photos of, I used a real ruler for the 100%, but realise a photocopy would be better.
The vernier scale at 1m from the screw. It is sellotaped on. ± 2mm is fine (± 0.2% uncertainty is negligible compared to the extension and area)
Wear goggles, but you also need some protection from flying wires (not such an issue with copper, but other alloys can store a lot of energy). These cardboard pieces help prevent the wire from flying around. e.g. with 32swg copper you 1-10N is fine and prety safe if it breaks, but with nichrome you might want 1-40N in 4N steps which is altogether more interesting if it snaps.)
I use a 10g hanger to tension the wire so that there is a nice talking point about the ice hockey stick shape of the graph (a false extension on the first weight because it is taking up the slack and pulling out kinks). Note the hanger is near the floor and there is a sandbag in case the weights fall: it stops you putting your foot there more than protecting the floor.

For those of you who assess against CPAC, this is a good experiment for 3a (Identifying Risks) and 3b (Working Safely). I use the Hazard | Risk | Control approach to a risk assessment. e.g.

HazardRiskControl
Wire breaking.Flailing wire causing damage
to exposed skin/eyes.
Weight falling on feet.
Eye protection.
Weights over wire for kinetic
energy transfer.
Sandbag on floor.

I realise that the weights on foot issue is not a massive one, and using copper wire makes the flailing wire unlikely too, but they do need practise thinking about these things for bigger challenges ahead.

The main pfaff is getting the top ruler (the scale) parallel with the wire. The bottom ruler is just raising the vernier to the height of the top scale. I now realise I could dispense with both rulers and use a 100% photocopy (or thinner ruler!) for the scale.
This reading would be 828.8mm.
Normal micrometer screw gauge practice for the diameter (three times). Check the micrometer for zero error. I would do a whole lesson on micrometers well before attempting Young modulus, and would give a few a nice zero error using the little adjustment spanner that comes with them. Area is πd²/4 (rather than finding r, which just introduces another opportunity for mistakes). Uncertainty here (assuming a perfect zero) is ± 0.005mm (it is a reading) or 1.9% for the diameter so 3.7% for the area, which I would round up to 4% (I always err on the side of caution).
My lab book, but before I stuck in a screw instead of using a G clamp! With 1m of 32swg copper you get about 1 mm extension per 4 N weight on the wire. The wire starts to slip at around 10-13N, and the general guidance is 5 < number of readings < 10 so the whole experiment can comfortably be done with one hanger with ten 1N weights on it. Assuming we discount the first couple of readings, making 2N our “zero” the uncertainty in the first real extension (2 to 3N) is ± 0.1mm on 0.3mm or 33%, but this reduces so by the fourth point (2 to 6N) the uncertainty is ± 0.1mm on 0.9mm or 11%.

Three graphs of real data showing how the pulley (middle) makes no difference, the first and third are with the wire simply hanging over the edge of the plank. The final one (green dots) is Hooke’s Law.

I also made a video.

I hope you found this useful. Any comments, suggestions etc. Please contact us through twitter on @physicstp or use the form below.

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29. Measuring the Young Modulus

Thomas talks Robin and Patrick through his method of measuring the Young Modulus that can be done as an individual experiment rather than in groups.

Timestamps

  • Disclaimer @ 00:00
  • Episode starts @ 01:22
  • Physics in the News – James Webb Telescope update @ 03:40
  • Remember the Survey @ 05:04
  • Measuring the Young Modulus @ 05:45

Summary

A brief cameo from Thomas’ daughter who is staying with Patrick Kaplo kicks off the podcast and leads to a chat about interns in American Schools before Thomas steers back to the James Webb Telescope which has cleared its final Thermal Vacuum test. Then on to the topic of the day – how to measure the Young Modulus as a class practical with minimal equipment. Thomas has blogged about this in detail and also had a go at making a video!

Join in!

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.

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

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28. Maths in Physics, What’s the Point?

We discuss what’s gone well and badly this week with guest presenter Cara Wood and then chat about James de Winter’s thoughts on Maths in Physics teaching.

Timestamps

  • Introducing the Survey @ 01:45
  • What’s gone well and badly this week? @ 02:46
  • James de Winter interview @ 08:50
  • Post James chat @ 25:12

Summary

Cara Wood (she of the plucky string in episode 27) steps in for Patrick Kaplo to share her thoughts about what has gone well and badly this week. James de Winter then talks about Maths in Physics teaching: what can learned from the Maths department and the challenges Physics Teachers face. He mentions research by the ASE about cooperation between Maths and Physics departments and also Ed Southall’s book “Yes, but why?”. He also talks about how he has used numberless graphs and suggests a question you can ask yourself before each activity: What’s the point?

Cara reminded Thomas about the graph scale selector, but we couldn’t find a link to an example, can you?

Join in!

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.

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

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Podcast Publish Fails

I think I am getting a bit blasé about publishing, two fails in two weeks. 😬

When I create a Podcast Post I have to do three main jobs for the podcast to release properly:

  1. Upload and attach the mp3
  2. Tell the Post when to go live (5:00am on the next term-time Thursday – an arbitrary choice that I have stuck to)
  3. Tell the Post it is a Podcast Episode (rather than a blog etc.)

Last week I failed at #2, this week I failed with #3. Both cases were because I changed the auto-tweet text. For some reason you have to completely start again from scratch if you want to change the release auto-tweet. This means copying and pasting all the content in to a new page, usually late at night, usually a bit frustrated…

I am making a checklist now. #1 is

“Check the damn tweet doesn’t have a spelling mistake!”

Enough procrastination. I have a pile of lab books to mark. 😖

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27. Ways to teach… Waves

Thomas, Robin and Patrick introduce and discuss many ways of teaching waves that have been shared by the listener.

Timestamps

  • Physics in the News – Blue Origin @ 01:07
  • Ways to teach… Waves @ 01:50
    • Cara Wood and a piece of string @ 02:20
    • Slinkys @ 06:50
    • Making many nodes @ 10:54
    • Salt Pendulum @ 13:47
    • Acetates @ 14:58
      • Jed’s wave visualisation experiment @ 16:48
    • How to remember the difference between Transverse and longitudinal @ 18:59
    • Alom Shaha and the Jelly Baby Wave Machine @ 20:17
    • Standing waves @ 24:51
    • Ruben’s Tube and Kundts Tube @ 28:01
    • Showing colour mixing and projector polarisation @ 30:43
    • Young’s slits – lab scale with sound @ 32:47
    • PhEt @ 33:38
    • Mexican Wave @ 34:20
    • Tell us misconceptions! #tptpmisconception @ 35:25
    • Who won Alom Shaha’s Book? @ 37:43

Summary

Patrick, Thomas and Robin get together to tackle ways to teach waves but not until they have touched on Jeff Bezos’ bid for extra-terrestrial adventure: Blue Origin.

Cara Wood was first up sharing tips for teaching waves.  She introduces waves by simply getting students to pluck a piece of string held in their teeth, so that they can see, feel and hear vibrations, experience amplitude and frequency, and discuss waves travelling through solids and gases.  Patrick loved this: really giving a tactile encounter with waves and their source.  Robin made the tenuous link to cochlear implants.  Very similar is the metal coat hanger demo.

“You can’t beat a Slinky” according to Dan Toomey – thanks Dan!  Patrick put us onto “Snakey springs” on amazon for a mighty £27, but we found them cheaper with a bit of persistence: £5.75 at Select School Supplies. Snakey Springs help to avoid Slinky tangles when demo-ing transverse waves.  Thanks to Graham Thomson for the tip of setting a ball next to the slinky spring so that it gets struck as the wave passes and you can thus link frequency and energy.  Graham pointed out the rich discussions you can have on time period, frequency, wave speed and wavelength all with the Slinky.  Thomas was really impressed with Frank Noschese’s video using paper cups next to the Slinky to demonstrate constructive and destructive interference.  Robin recalled a similar method to this to demonstrate the vibrational link to sound waves.

Frank Noschese masters the Slinky

Thanks to Dr Joshua Griffiths and Graham Thompson who talked about challenging students to produce features on ropes and Slinkies, such as increasing numbers of standing waves and purposely frustrating by asking for high frequency, long-wavelength waves.  This gives a good discussion of why it can’t be done!

Thanks to all the other folk too numerous to mention, who also pointed us towards the Slinky as a ‘must-have’ for teaching waves.

Thanks to Dan Toomey for the salt / sand pendulum video.  Thomas was delighted to report he had already done this and Patrick was keen to have a go.

John Hamilton’s use of acetate wave traces to demonstrate superposition makes a tough concept much easier for students to visualise – thanks John!  Jed Marshall uses acetates to get across the tricky idea of wavefronts, alongside his ripple tank that students can struggle with and he kindly supplied a booklet to show how it worked. (photos below).

How’s this for a handy mnemonic for longitudinal vs. transverse?  Thanks to Chris Beason and K Physics 1.

Alom Shaha joined us for his PIM and he described his jelly baby wave machine. The video says it all: easy to make, and as Alom says, transformative in the teaching of waves! Reflection, refraction, amplitude and frequency – all easily demo-ed quickly and cheaply. Despite Jelly Babies being lost in translation, Patrick endorsed the machine and he still uses it, although the Gummy Bears may be past their sell-by date!

Signal generators, strings and vibration generators always go over well, particularly in conjunction with a stroboscope and Patrick described how he challenges students, not least through atmospheric use of Pink Floyd music! Don’t forget your Rubens tube too – it really helps discussing pressure differentials in sound waves. And if anyone has any tips to get the Kundt’s tube to work, let us know!

Paul from @PlanetReynolds on Twitter had a lovely dichromatic crystals demo which has “Wow factor” and his toppling dominos is a great way of demonstrating density’s effect on wave transmission. Just search on eBay for “optical glass cube” and “100 led finger lights“.

Thanks again to Dan Toomey for his tip on using superposition with loudspeakers, and don’t forget PhET, ripple tanks and “stadium waves”!

…and finally! Well done to Frank Noschese who we picked from the expensively engineered randomised name selection device. Frank will receive a personally signed copy of Alom Shaha’s Recipes for Wonder.

HAVE A GREAT HALF TERM!!

Join in!

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.

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A Swiss Roll

26. Finding Physics Teaching at Fifty-Three

Thomas, Robin and Patrick Kaplo hear from Jonathan Shaw, a late career change to Physics teaching who is in his NQT year at 53 years old. Jonathan also challenges the team to select the most important equipment for a new physics department.

Timestamps

  • Vacuum cannon update @ 00:39
  • Ways to teach… Waves reminder @ 01:04
  • Physics in the News: Coal Free Electricity in the UK @ 02:39
  • Energy storage with cars @ 03:56
  • Jonathan Shaw, NQT @ 04:47
  • After the interview discussion @ 20:40
    • Swiss Roll @ 20:44
  • Which equipment should a Physics department have? @ 29:35

Summary

Thomas reminds us that the Vacuum Cannon can once more be ordered in the shop (for delivery in early June). Physics In The News leads to a chat about the UK’s coal-free week and the idea of load balancing with electric cars. This week’s guest is Jonathan Shaw, a successful businessman and entrepreneur who found his true calling as a Physics teacher late in life. What he says challenges Patrick, Thomas and Robin to justify practical work and also to come up with the equipment that a Physics department should have if starting from scratch. Robin gives his top tips for teaching other teachers to use oscilloscopes but is sceptical about a virtual oscilloscope but Thomas recommends the one at academo.org. Share your list with @physicstp on twitter with the hash tag #tptpequipment.

Ways to teach… Waves

Episode 27 will be all about ways to teach Waves. How do you do it and what works best for you? You have until Saturday night to give us your ideas, and one of them will win Alom Shaha’s excellent book Recipes for Wonder.

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.

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25. Fusion, Triangular Teaching and Avoiding Dead Leaves

Thomas, Robin and Patrick Kaplo discuss the re-release of the vacuum cannon, the ITER fusion project, Prof W Brian Lane tells us his PIM and James De Winter talks about avoiding “Plugging and Chugging”.

Timestamps

  • Welcome back Patrick Kaplo @ 00:37
  • The Vacuum Cannon is back @ 01:10
  • Physics in the news: ITER and fusion @ 02:07
  • Prof. W Brian Lane and his Spring Lab @ 04:23
  • Differences between US and UK systems @ 13:21
  • James De Winter and Maths in Physics @ 20:24
  • Please give us some Waves teaching tips @ 27:31

Summary

Patrick Kaplo joins the team once more. Thomas announces that the Vacuum Cannon can once more be ordered in the shop (for delivery in early June). Physics In The News leads to a chat about Fusion at ITER and how it is always 25 years away. Thomas introduces Prof. W Brian Lane who first appeared in Episode 20 (Ways to teach… Displacement, Velocity and Acceleration). Discussing it, Thomas and Patrick get a bit sidetracked talking about our different systems before Robin steers them back to the idea of teaching with a triple whammy of Theory, Simulation and Practical. Thomas then plays a short section of a chat Robin had with James De Winter about the place of Maths in Physics and avoiding “Plugging and Chugging”.

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

Ways to teach… Waves

Episode 27 (assuming we make it) will be all about ways to teach Waves. 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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24. YouTuber Lewis Matheson and A Level Physics On-Line

Lewis Matheson tells how he gave up classroom teaching to become a YouTuber with his channel A-Level Physics On-Line.

Timestamps

  • Ways to Teach… Waves reminder and new competition @ 01:18
  • Physics in the News: Accelerating Universe Expansion @ 02:31
  • Lewis Matheson interview @ 05:56
  • Post Interview chat @ 21:49

Summary

Physics in the news this week is the improvement of the evidence that the expansion of the Universe is accelerating. This leads to discussion of how distant galaxies are going to disappear over time, but also the Infrared Catastrophe. The main interview is with Lewis Matheson, ex-Physics teacher who is now a full-time podcaster with his website A Level Physics On-Line and its related YouTube Channels.

Join in!

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.

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

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23. Minds-On as well as Hands-On: Alom Shaha

Alom Shaha talks about his book “Mr Shaha’s Recipes for Wonder”, his love of Practical, the videos he makes to support teachers and equality.

Timestamps

  • Physics in the News: Black Hole Photo @ 01:01
  • Katie Bouman @ 2:24
  • Emails from listeners @ 06:29
  • Announcing the next Ways to teach… episode @ 08:29
  • Alom Shaha intro @ 10:06
    • Recipes for Wonder @ 11:42
    • Parents are the first teachers @ 12:29
    • Alom’s Videos and helping teachers of Physics @ 23:00
    • Inclusivity @ 31:55
  • Competition! @ 38:02

Summary

Physics in the news is (of course) the recent first ever photo of a Black Hole by the Event Horizon Telescope; Thomas mentioned the XKCD cartoon that gives its scale. We then thanked some listeners who have contacted the podcast before introducing Alom Shaha. Alom has (with Emily Robertson) created a book for Primary Age children that encourages them to do Science with their parents: Recipes for Wonder. Alom also has a YouTube channel (Sciencefilms) that is aimed at teachers. Alom had a lot of interesting things to sy so this is our longest episode yet.

Join in!

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.

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

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Links for Technicians

We were contacted by Seamus Smith who told us about some more sites for Technicians. I have just slightly tweaked the site to have two more pages in the menu structure: Technician Sites and Physics Teaching Sites.

One of the sites Seamus mentioned is TecHKnow which has a huge directory of sites, that makes our pages look a little weedy. But on the basis that anything that links back to them helps, I am leaving our pages up.

I am still searching for the motherload on Physics Teaching sites. If you know it, please let us know using our twitter handle @physicstp or the form below.

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