Tuesday, April 13, 2021

Teeeeter Totr

Just a quick balanced torque puzzle. It's really a test of whether or not one truly accepts the concept of center of mass.

Nothing exotic going on. The meterstick is uniform. Sufficient information is provided to solve the puzzle. It can be confounding to students.

Teeeeter Totr - HTML export | movie export

UPDATE: Among the many things I can count on in life is that virtually any mechanics demo I might share here has already been done better by the inimitable Dan Burns. For example:

Sunday, April 11, 2021

RT;DL Pixel Peeping

Screens. When I was in school, screens were reflective white, flat curtains pulled down from retractible rolls when the teacher was going to show an educational film on the reel projector they shared with the other teachers at the school.

At home, screens were cathode ray tubes in which a spray of electrons, steered by magnetic fields and attenuated by a shadow mask, struck red, green, and blue phosphors. The high-pitched noise given off by the electronics of a CRT TV monitor create physical pain in modern-day students. TV watchers of a certain age somehow tuned that 10 kHz+ whine out.

Today, screens are everywhere, and virtually all are based on light-emitting diodes. But the RGB nature of color imaging remain. That's what this activity is about.

Color mixing and pixel geometry. Surprising enough and instructional enough to be worthwhile.


Pixel Peeping Student Document (Google Docs copy link)

Pixel Peeping Magnifier Observations - HTML export  |  Movie export
(media links are included in the student document)

The PhyzSommelier says this activity pairs nicely with

PhyzLab Springboard - Fun With Colors (Google Docs copy link)


Saturday, April 10, 2021

Thursday, April 08, 2021

In the George Floyd trial: Audio Pareidolia

Humans are so good at finding patterns, we often find patterns where none exist. This phenomenon is referred to as pareidolia. 

Add to this the power of suggestion, and things get even more interesting. The back masking panic was fueled by audio pareidolia. As was EVP: electronic voice phenomena, a means by which ghost hunters fool themselves and others.

I made a presentation on the audio version of this phenomenon and deployed it during our unit on waves and sound.

It was all good, wholesome, laughable fun. And then it showed up in the trial of Derek Chauvin. I have updated the presentation to reflect this latest incident. I placed it at the vary end so that by the time you get there, you'll recognize exactly what's going on.

Back Masking (HTML export)

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 Student Document - Google Docs copy link

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.

Water Waves in an Electric Sink (Google Docs copy link)
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.

High Quiet Low Loud (Google Docs copy link)
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 - Student Document (Google Docs copy link)

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.