## Thursday, March 25, 2021

### Polarized Black Hole Image

It's probably irresponsible for me to post this wee package that might deliver more questions than answers. Nevertheless.

## Saturday, March 20, 2021

### RT;DL Physics in the Fountain of Fizz

The Diet Coke Mentos geyser made a big splash in popular media before social media was a big thing. I was keen to incorporate it into my curriculum, but needed a content-based hook. Mythbusters (among others) focused on the chemistry of the spectacle. That was entirely cromulent: it's the engine that drives the demonstration.

But I teach physics. And there's plenty of physics to exploit. Between the beginning and end of the eruption, some quantity of mass is ejected. Mass flow rate? Check. The fizz emerges from the bottle with some speed and reaches some altitude above the launch point. Energy conservation? Check. Determination of muzzle speed from maximum height? Check. Total energy dissipation approximation? Check. Power approximation? Check.

My school is a 1960s-era low-slung, sprawling campus. Determining the maximum height of the eruption is non-trivial. Most buildings top out at about three meters. We do have an accessible tall (~6 m) wall made of cinder blocks as part of our gymnasium. So that's what we settled on.

Initial mass is measured. Video is captured. Final mass is measured. The video is analyzed. Calculations are made.

Fountain of Fizz Observations - HTML Export | Movie Export

Media links are included in the student document. The movie export is included for use on devices that struggle with the HTML export.

### The Rainbow Connection—To Physics

Science Friday had a nice segment on rainbows.

The Rainbow Connection—To Physics

Seventeen minutes well-spent. Discussion includes tertiary and quaternary rainbows, why Hawaii is the rainbow capital of the world, and what rainbows might look on other planets (oh, that's a good one!).

## Friday, March 19, 2021

### Eight Days A Week

Here's a lesson plan organizer spreadsheet. It shows the classes I'm teaching and the cohorts assigned. All I need to do from here is flesh it out with some quality lessons.

Rinse and repeat. The sheet below accounts for the week of March 22. There will be 16 lessons each week for the remainder of the school year. Just gotta write 'em down and roll 'em out.

And then you woke up.

Actually, there are adult humans who imagine that this is something I will or should be doing. The coronavirus and "kids out of my house now!" fever have conspired to suffocate their logic and reasoning skills.

Looking at that planner again, realize now that I left out the engaging but purely asynchronous lessons I need to prepare for Wednesdays. Good thing I can go back and edit those in.

Addendum 1: You might wonder why this is so much worse than pre-pandemic in-person instruction as it was in the Before Times. I have taught all of these courses before and know how to make each one work in-person. Those courses benefited from my 35 years for experience in the physics classroom.

Pandemic instruction throws me back to being a first-year neophyte in many ways. I have never worked so hard to be so ineffective. Not even in my first year of teaching in 1986-87.

Now it's hoped I can develop yet another thing that's never existed before: robust lessons for students who are physically distanced and thus cannot work in groups—but who are physically present in the science classroom.

In addition to running the distance learning lessons that I have also never done before.

I'm sorry. I cannot do these things. Asking me to do them is abusive. I am already destroyed from the school year. I never had miracles to offer, and I certainly don't have any now.

Addendum 2: Instructional time for each course has been reduced from 288 minutes per week (59x2 + 123 + 47) pre-pandemic to fewer than 200 minutes per week (90 + 90 + 15) to 100 minutes per week (50 + 50). We lost one third of our instructional time for most of the year and will lose two thirds of our instructional time for the remainder of the year.

The district has worked hard to make sure students cannot access wifi on campus. Go ahead and re-read that if it didn't sink in on the first read. And after eight months of device-based instruction, the district expects that students electing to take their instruction on campus to go device-free for that instruction. District administration truly does expect "different but equal" in-person vs. remote courses to be prepared and implemented by instructors.

No.

Addendum 3: Hybrid Cohort Logistics. In the future, people might not believe the contortions implemented by school districts. Best to document them while they're fresh in our minds.

A. The Weekly Schedule of Cohorts and Classes. Yes, I designed this myself. Color mixing and font choice were intentional.

B. The Daily Bell Schedules. The most important consideration here was that the start and end times matched the school's pre-pandemic start and end times. It's important to have priorities.

## Wednesday, March 10, 2021

### RT;DL Introductory Wave Activities

At this point, I think we all have our own favorite PhET sims. You might be able to start a fight among physics teachers by proclaiming your favorite is the best PhET sim of them all. But honestly, what's not to love about John Travoltage

Actually, I think Wave Interference is my favorite. (Energy Skate Park fans are now unfollowing me on Twitter.)

When we get to wave optics, we use the light module to develop interference pattern mathematics. As we begin the study of mechanical waves, we explore representations in the water wave and sound modules.

Students begin with examining a pulse with the sim's various view modes. Then it's on to continuous wave trains while varying frequency and amplitude.

Originally developed for use with Pasco's Waveport DataStudio software, this activity has been redesigned around Wave Interference's sound module. This time, the manipulation of amplitude and frequency is accompanied with audio feedback. The sim's "Particle View" feature shows that matter doesn't move much even as a wave propagates across greater distances. Diving deeper, we notice that our sound waves appear to be moving through a solid in the sim.

I couple these with The Mechanical Universe - Episode 18: Waves and Paul Hewitt's Conceptual Physics Alive! Vibrations and Sound I and Vibrations and Sound II to round out much of the introduction to waves.

In any case, I'm sure there's even more to PhET's Wave Interference than I am leveraging. So much groovy wavy goodness!

## Sunday, March 07, 2021

### RT;DL Magnetic Electricity

The immediate follow-up to the Electric Magnetism activity is the Magnetic Electricity activity. As one might expect, Electric Magnetism explored the ability to produce magnetic fields using electric currents. Magnetic Electricity moves on to using magnetic fields to produce electric currents, with an emphasis on "moves".

Induced current and turning motors into generators are at play in this one.

Magnetic Electricity Observations - HTML Export | Movie Link

Media links are included in the student document. The HTML export is preferred. The movie export is available for use on devices that struggle with the HTML export.

## Saturday, March 06, 2021

### RT;DL Electric Magnetism

With Ørsted's Discovery, we established that electric currents are surrounded by magnetic fields. In this activity, we extend that to the design of electromagnets and motors. In our traditional, In-Person Learning electricity and magnetism sequence, we would have used our Genecon hand-crank generators to power electric circuits. In short, we would have been familiar with their utility as generators. Here we turn the tables so that the Genecons become motors.

This one is also a bit fiddly in class: St. Louis motors are great, but students will discover all the ways they can go wrong. I don't think that's a bad thing, but there is frustration in the room. You lose that in the RT;DL version. You lose a lot in most RT;DL activities.

But it's a nice sequence of observations, building on Ørsted's Discovery and setting up the next activity: Magnetic Electricity.

Electric Magnetism Observations - HTML Export | Movie Export

Media links are included in the student document. The HTML export is preferred. The movie export is available for use on devices that struggle with the HTML export.

Enjoy my lack of professional production sets, lighting, and technique. These are all shot in my classroom using classroom apparatus and lighting options, and shot on my iPhone 8. Presentations are created in Apple Keynote and exported as HTML and exported as a movie.

One More Thing: I just noticed this delightful bit of apparatus available from Arbor Scientific. Simple and effective for working out the right-hand rule for the magnetic force on a current-carrying wire.

## Monday, March 01, 2021

### RT;DL Ørsted's Discovery

This activity explores the magnetic field around a current-carrying wire: Ørsted's Discovery. It's a bit fiddly when we do it in the classroom. The compasses can be thrown off by steel spines and/or leg plates in the tables. To be honest, I've seen compass behavior I cannot explain in my classroom. Perhaps strange things happen to our compasses while they're stored during the off-season. They are stored in proximity to bar magnets.

In any case, I got passably reasonable behavior from my compasses as I recorded the videos for the RT;DL observations of this activity.

Because I was recording the observations on behalf of the students, I provided them to the students in a disorganized way. Students would need to match the randomly sequenced observations with the called-for observations in the activity instructions. It's RT;DL ... you do what you can.

The HTML reports are preferred; the movie exports are provided for users whose devices struggle with the HTML exports. Links to all media are embedded in the student document.

Apologies for any clumsiness that comes through in the videos. The physical geometry required for recording these events is awkward, and I really didn't invest much time in rehearsal. I was happy to get decent light on my subjects.

Ørsted's Discovery Part B (3D) - Movie Export

Ørsted's Discovery Part A (2D) Observations - HTML Export | Movie Export

Ørsted's Discovery Part B (3D) Observations - HTML Export | Movie Export