Monday, September 28, 2020

RT;DL Cannonball - Ball dropped from moving ship

Another classic demo that can elicit excellent classroom discussion. A cannonball is dropped from the mast of a moving boat. Where will the ball land? This nicely confronts our inner Aristotle.

In my version, the premise is laid out, the landing point options are described, and students are asked to produce arguments supporting three of the five possible landing sites: one that they believe, and two they could convince others of (as good attorneys).

A straw poll is conducted (now with Zoom participant reactions), then students are asked to defend their various positions. After the classroom discussion/debate, a final vote is taken. 

I warn them to vote carefully. "Physics is a democracy, and whichever outcome gets the most votes will  be correct. The universe will accede to our wishes. Please vote responsibly!" [Update: at some point Zoom made participant reactions ephemeral, so they lost their value as an instant polling tool.]

Then we see the actual outcome. First in my animation; eventually in the classic Project Physics footage from 1968. In face-to-face instruction, I also carry it out using a discontinued Pasco product (Ballistic Cart Accessory with Ball Drop Attachment). So sad to see that combo go.

Lastly, I ask students how the demo could be altered so that the ball would land at the other locations that were offered in the premise. The 1968 footage shows one such modification. I leave it to students to think of the others.

Cannonball [Virtual Demonstration] free resource at Teachers Pay Teachers

Student document (Google Docs file on Google Drive)
Presentation link embedded in student document
Answer key

The HTML export from Apple Keynote had a few wee quirks this time. Mostly in that while most of the splash sounds are muted, the audio from the 1968 video (muted in my preso) comes through loud and clear in the export.

Further discussion in the comments.

Sunday, September 27, 2020

RT;DL The Clever Dumbbell - Tension & Inertia Demo

A classic and popular demo. I do it in Conceptual Physics, Physics, and AP Physics 1. And I use a 5-lb dumbbell and kite/packaging cotton string. For years, I used a cast-iron dumbbell. But I broke floor tiles on occasion, and there was that one time the wheel-like nature of the dumbbell ends allowed it to roll onto a student's open ... toes. So I found rubberized hexagonal-end dumbbells. And I use a cardboard catch-box with scrap paper to protect the tiles.

After posing the initial question: Which string will break when the bottom string is pulled, I have them work through some leading questions.

Instead of having students predict which string will break, I have them request a string for me to break. Once they understand this paradigm shift, they request the bottom string. And I oblige. Eventually I break the top string, too. This can be navigated in the preso, alone. But I prefer to do the demo in my empty classroom because I can.

The efficacy of this demo lies in the dependence of the outcome on the presenter's technique. If it were a 50-50 coin flip each time, the demo would not have any pedagogical value. Some ponderables are offered post-demo, too.

As is a continuing theme in my RT;DLs, the student sheet is a Google Doc and the preso is an Apple Keynote preso, exported to HTML. These exports work delightfully on computers. Less well on tablets or phones. 

This one takes a bit of practice to navigate. 

Things shown in images but not in words: strings break when they are stretched beyond their limit by tension greater than the sting can withstand. A rapid pull stretches the bottom string through its limit before the dumbbell moves very much, thus keeping the top string from being stretched. A slow pull allows the top string to be at greater tension than the bottom string, allowing it to reach its limit before the bottom string does.

Student document (Google Docs file on Google Drive)
Observations presentation (linked to on student document)
Answer key

Saturday, September 26, 2020

RT;DL Blowout: A tour through the equations of motion

Near the close of the last century, I wrote an article for The Physics Teacher extolling the unadvertised virtues of Pasco's Lenz's Law Demonstration tube. 

Sure, you could use it to demonstrate Lenz's law, but that fine aluminum tube seemed pricey, so I was keen to justify the expense. You can tap it with a mallet (or on the ground) while holding it at various places to produce different notes. The Q of aluminum is great for this. You can stand it up on its end in your classroom to demonstrate unstable equilibrium. 

But for my notion of classroom theatrics, the best unintended use for the tube was as a blowgun. 

For this RT;DL I prepared a tour through the equations of motion with the blowgun acting as my vehicle. it is very much up to the task. I do this in my AP Physics 1 course only. Regular Physics students don't really need the exercise in number puzzles that the equations of motion afford. The year's too short.

In any case, I blow a marker pen through the tube and arrange two photogates near the muzzle to help determine the exit speed. It's over 60 mph!

Once the exit speed is determined, we figure out the acceleration of the marker while it was in the tube. Over 20 g's.

We also figure out how long it took the marker to exit the tube once its motion began. Then we investigate where the marker was when it was at the half way point (in time) along its journey through the tube.

The preso is enhanced with photos and high-speed videos. And an instructive(?) blooper at the end.

Blowout Kinematics [Virtual Demonstration] at Teachers Pay Teachers includes

Student Document (Google Docs file)

Student Lesson (HTML)

Instructor Preso (HTML)

Exploratorium friends, Don Rathjen and the late Paul Doherty, turned the blowgun idea into a nice Snack: Marshmallow Puff Tube.

Wednesday, September 23, 2020

RT;DL The Great Bullet Race

I run this demo in AP Physics 1. I don't run it in Physics. Why? Projectiles is not a topic I teach in Physics. We tend to spend more time in kinematics than kinematics is due. It wasn't a big topic in California Science Standards Physics (RIP). It's not that big a deal in AP Physics 1. It's virtually non-existent in NGSS Physics. If you are among the few, the happy few—the band of brothers and sisters—who teach a year-long AP Physics C-Mechanics, have at it!

But physics teachers of all stripes love, embrace, and perhaps cling to our kinematics. Maybe after a decade of NGSS Physics and a generation of retirements, kinematics' star will begin to fade. I have my doubts. Kinematophilia seems to have inordinate inertia. </soapbox>

In any case, we still regard this demo as a classic. [We don't seem to have a universally agreed-upon name for it. Or if we do, I don't know what it is.] So when it came up this year, I spent some time in my empty classroom trying to get some useable high-speed footage. 

Here's the student sheet and preso I cobbled together. (The Mythbusters segment is included.) Oh, and where a prediction is called for, Zoom participant reactions are solicited (yes, no, go slower, etc.).

Google Doc: Demo - The Great Bullet Race

HTML Presentation: Demo - The Great Bullet Race

I found the embedded videos in this HTML export to be a bit cantankerous—practice before using in class. Arrow keys to advance. Clicking in a video activates a scrub bar at the bottom and allows you to scrub forward/backward in that video.

Maybe you can get some use out of these; maybe your district won't let you use it. Guns and bullets are discussed, modeled, and used.

[RT;DL is remote teaching; distance learning]

Tuesday, September 22, 2020

RT;DL Inertia in Action

[RT;DL is remote teaching; distance learning. Where we show our attempts to bring extant lessons into the COVID-19 era.]

In the old days of face-to-face, in-class teaching, we did a station lab activity involving inertia experiences. It was called "Inertia in Action."

I retooled it into a video-based demo in which small groups could view segments, discuss prompts, and record their ideas on a Google Doc. It may not be your cuppa. But it works for me, given the circumstances. 

Student document (Google Docs file that lives on Google Drive)
Observations presentation (link embedded in student document)
Answer key

Here's the video. It doesn't make much sense without the prompts.

Saturday, September 19, 2020

Physics with Dianna

Learn physics from Physics Girl, Dianna Cowern. 

If you really want to lecture over Zoom this year, godspeed. If you'd rather do ... anything else with your synchronous time, let Dianna nail down the basics for you. Feel free to supplement to your heart's content. But I'm confident Dianna can handle intro exposition more effectively than I can. This is what she does.

Dianna's Intro Physics Class: Trailer - Physics 101, AP Physics 1 Review with Physics Girl

Never taken physics before? Want to learn the basics of physics? Need an AP Physics 1 review before the exam? This course is for you!
In this class we will cover these topics:
1D Motion
Free Fall
2D Motion
Newton’s Laws
Free Body Diagrams
Circular Motion
Gravity & Orbits
Energy & Work
Energy Conservation
Angular Momentum
Simple Harmonic Oscillations
Electric Charge
DC Circuits

Monday, September 07, 2020

The Lessons of Phyz September 2020 update

Google Docs, Freebies, and Inadvisable Discounts

When the pandemic closed the schools, I scrambled like most teachers. Our worlds had been thrown upside down and there was an expectation that we'd simply "throw our lessons online," hold classes on Zoom, create YouTube channels of our lessons, etc., and leverage the best among the countless sophisticated online platforms intended to allow our instructional visions to flourish while engage students completely.

More like an old desert-dweller suddenly cast into a roiling ocean while helicopters flew by and dropped materials that, when properly constructed, would make a nice boat. Or... we were expected to build the plane while it was in flight.

In any case, I found that the simple task of assigning a video for students to watch while answering questions was suddenly a challenge. Things worked better if the question sets were in Google Docs format. I could easily assign them and grade them (if need be) in Google Classroom. Many had been in PDF format: not edit-friendly for student work.

So I began the tedious task of transforming my video question sets from their PDF or Word formats to Google Docs. When I finished the ones I was in immediate need to use, I worked on all the others I had posted at The Lessons of Phyz, my Teachers Pay Teachers store.

So here's what's available—an available in Google Docs format, most sold separately or in bundles (at an inadvisable discount).

The Mechanical Universe (All 52 episodes)

The Mechanical Universe High School Adaptations (All 28 Episodes)

Conceptual Physics Alive! with Paul Hewitt (All 34 episodes)

YouTube Physics (quite a variety of topics covered)

Physics Modules (Mechanics, Heat & Temperature, Waves & Light, E&M, and Modern)

Skepticism (we need this so much right now)

Breakthrough: The Ideas That Changed the World (All 6 episodes)

Cosmos: A Personal Voyage (Carl Sagan's 1980 series, all 13 episodes)

Cosmos: A Spacetime Odyssey (Neil deGrasse Tyson-hosted 2014 series, all 13 episodes)

One Strange Rock (Will Smith-hosts, great for NGSS "The Living World" biology, all 10 episodes)

Our Planet (Think Planet Earth, but with an edge, all 8 episodes)

How Earth Made Us / How the Earth Changed History (Excellent BBC series, all 5 episodes)

Earth Science (Mapping, Atmosphere, Water, Weather, Human Impact, Geology, Solar System, Galaxies)

Pandemic: How to Stop an Outbreak (2020 Netflix series, all 6 episodes)

Two dozen resources are free of charge. Bundles are often discounted so heavily that I get a warning from TPT that I've gone too far. If your school has licensed TPT School Access, then I suppose all the resources are free for you.

Not long into the pandemic, TPT created a method for converting PDFs into Google Docs. By the time it was available to sellers, I was already too deep into the pain-staking process of converting them myself by hand. Well, by computer, but you know what I mean. So I just plowed through into the summer until everything in my store was converted.

I hope you find something that can help you this year and beyond.

Saturday, September 05, 2020

Kinetic Karnival now on YouTube

Here's a post from 2009. Updated as I've added the videos to my YouTube channel. I downloaded them from Jearl Walker's MySpace page, where they were originally posted.

All six 30-minute episodes of Jearl Walker's classic television series, the Emmy-winning Kinetic Karnival, are available online at Walker's MySpace page. [Update: I can't access them on MySpace anymore, even in Chrome.] I recommend watching them before showing them in class, although I'm sure you'd do that anyway. There are a few brief moments that modern educators might find objectionable. Most of us find ways to work around such moments, but it's always best to be aware.

I developed video question sets for episodes 1, 2, 3, and 5. Students answer them while the video is in progress. They're up as PDFs in The Book of Phyz.

Here's a one-stop collection of Kinetic Karnival links for your convenience. If you like question sets matched to science videos, The Lessons of Phyz is the place for you.

1. Forces and Collisions [impact time and contact area]
In this episode, Jearl proves his virility and masculinity by chopping concrete bricks with his bare hands and volunteering as the meat for a “nail sandwich.”

Kinetic Karnival - Forces and Collisions - Question Set - Key
2. Rotation [circular motion and conservation of angular momentum]
I show this one in two distinct segments (one in my Physics 1 course, the other in AP Physics 2). The first third is devoted to circular motion. The second two-thirds is devoted to angular momentum. Do I dislike the blending of these distinct topics? Yes. Do I have the talent and ability to produce my own series? Not so much. In any case, this episode features Jearl in a swim suit!

Kinetic Karnival - Rotation
Video Question Set 1 (UCM) 
Video Question Set 2 (Angular Momentum) - Key

3. Fluid Flow and Friction
In this episode, Jearl debunks the drain swirl myth from the bathtub, describes an early dating disaster, explains the tablecloth trick, and hangs a spoon from his nose.

4. Viscosity [non-newtonian fluids, quicksand, and corn starch]
Jearl enjoys tinkering with viscous and non-newtonian fluids. He gets stuck in quicksand and jumps feet-first into a pot of unflavored gravy.
Video [Sorry, I didn't grab it when I should have.]

5. The Leidenfrost Effect [heat transfer and phase change]
Arguably the best program of the series, though it does contain a "politically-incorrect/racially insensitive" moment. When Jearl complains about "the problem" with iron-cooked crepes, you might find the mute button on the remote control of your playback system. A few moments of mute will spare you an apologetic discussion afterward. Features the hand into molten lead, liquid nitrogen in the mouth, and firewalking.

6. The Science of Cooking
Jearl prepares a meal for a dinner date with a young lady. Along the way, he describes the physics and chemistry of a variety of dishes. And the date turns out as you might expect.
Video [Sorry, I didn't grab it when I should have.]