31 March 2020

Mail time: What equipment did I use for rotational motion demos?

Edna fan art by @aldescery
On the March 25, 27, and 30 AP Physics 1 youtube review shows, I used some equipment to make angular velocity-vs. time graphs, and to spin my pet hippopotomus Edna around on a rotating  platform.

Julia was one of many physics teachers who asked, where did I obtain the rotating disk (from show #1) and the rotating platform (from show #4)?

Julia and everyone, I'm so glad you're watching!

The Pasco rotary motion sensor can make angular position, velocity, and acceleration vs. time graphs.  I have the new wireless version, which works via bluetooth with my phone or ipad on the free "Sparkvue" app.  That's what I used when I had the two objects connected by a string over a disk.

The rotational platform is a big investment.  When we built our new science building in 2012, I had a nearly blank check to buy equipment - so I bought the Pasco complete rotational system.  Just the base and the disk attachment would be enough.  It's structured so that a Pasco-branded photogate can mount beneath the disk and measure angular velocity rather, um, more elegantly than I did on Monday's show.  But I only have Vernier-brand photgates, which don't fit.

When I did my open lab for teachers a few years back, we spent a few hours taking a trip to the hardware store to create the $5 version of this rotation system.  Get some 1/2 inch PVC pipe and two 90-degree attacher joints.*  Make a "T" out of the PVC.  Place the bottom part of the T over top of a securely-mounted ringstand... the top of the T will rotate pretty cleanly.  You can wind a string around the PVC to provide a torque, just like I did on Monday's show!

*Can you tell from the language use here that I have no skills with hardware? 

3 comments:

  1. Brad Williams showed a brief video of his $5 version on twitter: https://twitter.com/bwilliams025/status/1245050610359119877?s=20

    Awesome, Brad, thank you!

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  2. If you built the PVC version again: We built something similar at a training, and superglued a glass marble at the middle of the "T", so the ring stand rubbed on the marble instead of the plastic... surprisingly low friction for a DIY set up.

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  3. FOUND IT - the massive red pulley is here: https://us.vwr.com/store/product/8871512/demonstration-rod-mounted-pulley

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