RT;DL Seeing Magnetic Fields

This activity shows a magnetic field projectual being used to reveal the magnetic field around various configurations of bar magnets. As with all RT;DLs, this activity began as an in-class lab and has been retooled for online delivery. 

Seeing Magnetic Field - Movie Export

Seeing Magnetic Fields [Virtual Lab Experiment] at Teachers Pay Teachers includes 

Student Document (Google Docs file)
Observations and Mysteries - HTML Export (this link is in the gdoc, too)
Observations and Mysteries - Movie Export (for devices that cannot run the HTML export—this link is in the gdoc, too)
Answer Key (Google Docs file)

I will confess that I find watching iron filings slowly align with magnetic fields on a large screen to be calmingly satisfying. I suppose it's my ASMR.

Early Retirement

When I hatched it, I referred to my plan as “23AndMe,” like the genetics company. I would “graduate” (retire) in 2023, after teaching physics (and other things) at Rio Americano High School for 37 years. I was excited when my graduating class arrived on campus last year.

The CalSTRS numbers looked good. The last few years were going to be a bit bumpy, though. Physics, a course I've taught at Rio since 1986, was coming to an end. The vision of Next Generation Science Standards called for Physics to be replaced with Physics of the Universe (PotU). 

California published its vision of PotU, but textbooks and curriculum have been slow to emerge. The widespread expectation is that classroom teachers would absorb the NGSS PotU vision and leverage their creativity and ingenuity to develop curriculum ex nihilo. I had done some preliminary organizational work on how I would implement PotU at my school. But that first year promised to be an endeavor. There were two teachers at my school who could teach physics after I was gone. We met a few times to work on PotU.

In January of 2020 (years ago, now), my district offered a wee early retirement incentive to its oldest and most educated teachers. They hoped to clear out the highest paid faculty, easing pressure on a strained district budget. I looked at the numbers and was insulted. No way.

Then the pandemic struck. The district rescinded the incentive to those who applied for it. Many teachers retired without the incentive.

Our Last Day of School was Friday the 13th of March, 2020. Novel but unspectacular when it occurred. 

We have yet to return. Teaching is remote; learning is distant. It is awful. The school’s younger physics-teaching prospect moved to another district. An intended textbook adoption for all science courses was suspended.

For 2020-21, I had four preps: Physics, AP Physics 1, AP Physics 2, and Conceptual Physics. Transforming each of these classes to online versions has been ... difficult. And, to be delicate, the efficacy/effort ratio has not been high. I'm maintaining a headache that doesn't show signs of subsiding. My screen time exceeds any health-conscious dosage recommendations. 

In November, my district offered the same wee early retirement incentive. Same exact numbers as it offered in January. But they looked quite different to my newly throbbing eyes. Less insulting and more inviting. Bordering on irresistible. 

There's a significant pension prize if I stay the course for two more years. But here’s what I'm looking at. 

The course I polished over 35 years will be gone. A course I’ve never taught will take its place. There may or may not be a new textbook for the new course. There will be no 180-day curriculum with pacing guide/road map for this new course. No lab manual. No new lab materials. No test bank. Teachers might be given "release time" to develop such during the summer and/or during the year. Scratch that: there will be no budget for such extravagances. 

In fairness, this was what I walked into in 1986. I developed my course on my own, with direct and indirect help from mentors. And I was happy to do the work. Hard work. But I was bringing my vision of the course to life within my operational constraints. And I got better and better at loosening those constraints. The enterprise was enjoyable, challenging, and engaging. I was supported by the school and parents. I knew I was playing a long game, so I mixed patience with my determination.

What's happening now is different. I'm being compelled to implement a vision I was not invited to create. This has been true of the redesigned AP Physics 1 and 2 for a few years, and has not been enjoyable. Doing the same with the new Physics of the Universe does not appeal to me.

Predictions are difficult, especially when the future is involved. But it’s hard to see school districts in the next few years being flush with enough cash to fund curriculum development. Or anything else. We’ve had furloughs in the past. I don't see good times ahead for school district budgets. My district is keen to replace me with someone lower on the pay scale. The budget is prioritized over instructional quality. But that's always been true; you a priori-tize that assumption going in, and do well because it's important to you.

The recently-redesigned AP Physics 1 will certainly still be there. I haven't made a secret of my antipathy for that redesign and especially for the accompanying exam. But the College Board has convinced themselves that they are doing good in the world and so they will continue. Schools use AP courses to market themselves, so AP will continue as a thriving product line. I enjoy the course; I don't enjoy the test-prep aspect.

AP Physics 2 is a bit more on the bubble. It’s a tough sell, a second year of AP Physics in high school. My principal has made it a priority to run it, and I love teaching the material. To me, much of the AP2 material is more interesting than what we do in AP1. The district is in the process of adopting a new textbook for AP Physics 1 and 2. Our current textbook is ©2007 and was pretty shiny when we adopted it for AP Physics B in 2008. That was the last time we adopted physics books, now 13 years ago.

So two years of a developing course and one or two AP courses whose exams have lost their lustre. In a world of no books or piloting new books. With budget cuts looming. While we await full implementation of vaccines in a nation where anti-vaxxers stand loud and proud. 

Which part of that seems unappealing, right?

When I envisioned 23AndMe, Physics was transitioning to Physics of the Universe in a controlled manner with the participation of colleagues who would be left in charge of teaching it when I was gone. I actually designed the transition process for my school. The economy was such that I could expect a raise to be negotiated before I retired. And I had not experienced Remote Teaching/Distance Learning of four courses for the better part of a school year. 

There's more about short- and long-term issues that have altered my perspective, but this post has self-indulged quite enough (even for a blog post). Anything else I need to say will be posted in the comments. I'm dropping this post like a bread crumb in case I ever wonder "What was I thinking?" in the years to come. (As Sade once sang, "The rose we remember, the thorns we forget.")

I think it's time for me to turn the page and move on. As the implications of this life-change settle into my features, I feel some subtle tingles of a weight being lifted normal force being reduced. 

I'm 35 years into the career. No one who was working at my school when I arrived is still there now. "Early retirement" feels like a misnomer. CalSTRS estimates over 16,000 California teachers will be retiring this year.

Practical masking advice from Professor Marr

Rio Americano alum and Virginia Tech professor, Dr. Linsey Marr, was a guest on NPR's Science Friday. Host Ira Flatow asked her a tight sequence of practical questions, and she handled them all with aplomb. 

In my years of science lectures, colloquia, and conferences, I don't need that many fingers to count academics who communicate as effectively as Linsey Marr. And just because I'm biased, it doesn't mean it isn't true. Am I proud to the point of bursting? Pretty close. 

Judge for yourself:

Two Masks Are Better Than One - Science Friday 2/12/21 - Professor Linsey Marr (16:58)

Oh, and you'll get practical information on how best to handle the pandemic as it stands in February, 2021.

Just in time for Valentine's 2022!

Somewhere along the line I added four Scientist Valentines to my personal collection and failed to add them to the Flickr album. Why? I don't know. But I'm here to make it right. With ample lead time for Valentine's Day 2022. In any case, the collection expands from 24 to 28.

Scientist Valentines aficionados will have no trouble spotting the new items (two female; two male). I have a favorite, but I'm not saying.

Scientist Valentines

RT;DL Van de Graaff Demonstrations

What may turn out to be the most shocking (yeah, that didn't take long) aspect of my Van de Graaff demonstration sequence is how I could possibly have left your favorite VDG demo out. What was I thinking? By all means, let me have it in the comments—don't hold back.

Charging Ahead - Movie Export

If you can forgive me, I selfishly included all of my favorites. And they're not so bad. My favorites are ones I can mine for good physics that I believe my students can gather and grasp. 

Mop Head, Pie Tins vs. Styrofoam Bowls, Bubble Brigade (soap bubbles), Bad Hair Day, Green Wig, and I Blew My Top. Again, light me up in the comments for omitting the cool VDG demo you do.

There is also an explanation of how the generator works.

Charging Ahead [Virtual Demonstration] at Teachers Pay Teachers includes:

Student Document - Google Docs file

Answer Key - Google Docs file

Observations - HTML Export (linked to in the student document)

Observations - Movie Export (for devices that struggle with the HTML export)

RT;DL Electroscopia

Here is the second qualitative electrostatics lab redesigned and video clip enhanced for use in Distance Learning. The first was "A Pithy Matter" shown in a separate post.

For "Electroscopia," we swap out the pith balls for a can-form electroscope. These were sold with cardboard inserts with angle markings to make them more electrometer-ish. In practice, removing the insert allowed students working on opposite sides of the electroscope to see the pointer without obstruction. 

The activity works through a series of observations involving charge typing, induction, and the differences between conductors and insulators. It closes with some questions students should be able to answer with the benefit of evidence. 

There are appearances of the Fun Fly Stick, a latex balloon, and my head in this activity. Not to be missed!

Here's a taste.

Electroscopia at Teachers Pay Teachers includes:
Student Document (Google Docs)
Observations (HTML export, preferred—linked to in the student document)
Observations (Movie export for devices that struggle with the HTML export)
Mystery Objects and Mystery Charges Observations (link embedded in the Answer Key)
Answer Key (Google Docs)

In practice, students "ask for help" to summon the instructor to their breakout room. Once there, students request an Object or a Charge and identify their room number. The instructor shares their screen while showing the appropriate clip, then leaves the breakout room as students interpret the observations.

RT;DL A Pithy Matter

Sure, there's some kind of force involved in the rubbed plastic/pith ball interactions. But do we really need to consider it a whole new force? Isn't it just some form of gravity or magnetism? Let's experiment.

This qualitative exploration of electrostatics features: electrostatic attraction and repulsion, a triboelectric sequence (but we don't use the T-word here), an electrophorus (with pronunciation guidance), and two rounds of Pith Ball Ping Pong. What's not to like?

Let me just add that nothing—nothing—turned my most jaded, been-there-done-that high school seniors into elementary students more than this activity. When the pith balls started flying, their giddy glee was an involuntary reaction that expressed itself before they could so much as attempt to stifle it.

A Pithy Matter at Teachers Pay Teachers includes:

Student Document (print-friendly Google Docs)

A Pithy Matter - Observations (HTML export as linked within the GoogleDocs document). This is a sequence of video clips showing interactions between cloth-rubbed plastic and pith balls, with special appearances by an electrophorus (ft. slow-motion electrophorus ping). Here's the movie export of the observations for use on devices that struggle with the HTML export—link also included in gdoc).

A Pithy Matter - Special Observations (HTML export for use by the instructor). They will seem silly to experts with content knowledge, but they are actually critical for the purpose of this activity.

This activity was designed for use with video conferencing (e.g., Zoom). Students need to check in with the instructor to see the "Special Observations". It's a redesign of what was an in-class lab. I consider it a mark of success that I am able to use the same lab quiz (ported to Socrative for online use, of course) to assess student performance on the activity. 

The roughest edge for students in this activity is recognizing that the brick is far and away the "most gravitational" object in the apparatus and how it can be used in this lab. The instructions make an attempt to steer, but still... Once they get past that, most groups catch on to the value of the bar magnet. Most; not all. 

To the best of my knowledge, this activity is not duplicated or even simulated elsewhere in teh interwebz. No Pivots; no PhETs. I will be corrected in the comments if I am mistaken.

In Distance Learning, I'm everyone's lab partner in addition to being the instructor.

Inertia is how much, not if

Hello Blog of Phyz world! I wrote a piece for the Talkin' Physics column in The Physics Teacher's December 2020 issue. In the interest of sharing it more widely and outside of a paywall, below is the blog-ified version of that article. You can also find a pre-print PDF linked here.

Inertia is an elusive concept in physics, and it is occasionally used to explain similar-seeming yet different concepts. The goal of this article is describe two scenarios which are commonly explained using the word inertia, even though that same word is being used to describe two different phenomena. A discussion clearing up this ambiguity follows the examples.

Consider a block of frictionless ice in the bed of a flatbed truck, as seen in the figure below. If this truck begins to accelerate from rest, the ice will remain stationary with respect to the ground and eventually fall off the back end of the truck. Why does this happen?

Next, consider the two blocks on horizontal frictionless surfaces shown below. Ropes pull them both to the right with 10 N of tension force. Block A mass a mass of 1 kg, while block B has a mass of 5 kg. Which one has a greater acceleration, and why?

Inertia is often invoked to explain both of these examples. In the first, the frictionless ice block maintains its state of rest of because of its inertia. In the second, block B has a smaller acceleration because it has more inertia than block A.

The theme song for Bill Nye the Science Guy famously states that “inertia is a property of matter.” If we accept this Bill Nye maxim, then only the second example is truly a demonstration of the idea of inertia. The frictionless ice of the first example does not remain at rest relative to the ground because of any intrinsic property it has. Rather it stays at rest because of its lack of net interactions with other objects around it. The first example illustrates how matter behaves when interacting or not interacting with other objects, but it does not illustrate any property that matter has. In the second example, Block A accelerates more than Block B because of a property intrinsic to each block.

Similarly, Donald Simanek argues that most so called “inertia demonstrations” would better be classified impulse demonstrations. On the topic of the classic tablecloth pull demonstration, Simanek writes that, after viewing the demonstration, “The audience didn't see anything that showed that objects with different inertia (mass) behaved differently.” Instead, they saw that you could reduce the impulse delivered to plates by reducing the amount of contact time the plates have with the tablecloth. Again, we see a demonstration of matter’s behavior when interacting with other objects and not a demonstration of something intrinsic to matter itself.

In this view, inertia is a property that says “how much” rather than “if.” It does not say whether an acceleration will happen, but rather how much acceleration will happen for a given net force. For example, an object having an inertial mass of 5 kg means that, for every additional 1 m/s/s you want the object to accelerate, you will need to exert an additional 5 N of force. This is what we mean when we say that mass is a measure of inertia. It does not mean that it is five times better at maintaining a constant velocity than a 1 kg object. Both would be equally good at doing that if there is a net zero force acting on those objects, and both would be unable to do so if there were a net force exerted on them.

Perhaps, to bridge the gap between the two demonstrations, we may want to say that the intrinsic property inertia measures how little an object deviates from its inertial path when a given net force is exerted on the object. We could modify our frictionless ice in the truck example to demonstrate this idea. To do so, we would need to replace our frictionless ice with regular, boring ice with friction, so that there is a nonzero net force on it when the truck accelerates forward. We would also need to have two blocks of ice of different masses so that we could compare how much one deviated from its rest position relative to the other for a given friction force. Doing so would allow us to demonstrate than an object with more inertial mass deviates less from its inertial path than object with less inertial mass when the same force is applied to each. Inertia is a comparison of how much, not if.

Similarly, the tablecloth demonstration could be amended to be a true demonstration of inertia. It is not enough to pull a tablecloth out from underneath a ceramic plate to call it an inertia demonstration. If you instead pulled a tablecloth from underneath both ceramic and paper plates and compared the accelerations of each, then you would have a great demonstration of the property inertia. Both plates accelerated, but one acceleration more. Why? Because the plates’ inertias differ. In this example, we are not saying that the ceramic plate remains stationary. Instead, we are saying that its change in velocity is less than the change in velocity of the paper plate. The emphasis is on the amount of change, not on whether or not change occurs.

In the end, it may be time to retire the word inertia altogether. Many physics teachers are comfortable requiring students to refine statements around gravity, asking them to “upgrade” their language from saying gravity alone to saying gravitational force, gravitational field strength, or acceleration due to gravity. Similarly, ambiguity surrounding inertia can be avoiding if we choose language that is more specific.

For example, one could say that Newton’s first law describes an object’s inertial behavior or the inertial path it may follow. These are not intrinsic properties of matter, but rather descriptions of how interactions affect what matter does. Inertia, in this sense, cannot be quantified. Newton’s second law, on the other hand, describes an object’s inertial mass—its resistance to acceleration. The inertial mass described in Newton’s Second Law is an intrinsic property of matter, and it can be quantified.

Like gravity, inertia is a broad and overarching concept. Saying an object has the property inertia is less clear than saying it has inertial mass. Saying an object moves at a constant velocity because of its inertia is less clear than saying it follows its inertial path or it is exhibiting inertial behavior. By improving our language, inertia can be both “how much” and “if.” We simply need to clarify which we are using and acknowledge that they are not the same. 

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in The Physics Teacher 58, 682 (2020) and may be found at https://doi.org/10.1119/10.0002746

RT;DL Things That Go Bump!

Which involves more force: stopping or bouncing? Let's demonstrate.

I inherited a stop/bounce dart when I arrived at my school in 1986. You arrange the dart as a pendulum and swing it into a wood block. Back in those days, you ran the unadorned nail point into the block for the stop, and attached a rubber stopped to the nail point for the bounce.

Since then, the advent of "happy" and "sad" balls improved this demo. And happy/sad pendula/mallets have been commercially available (help me out with a link if you know one).

Arrange the dart so that it barely knocks over the block using the happy ball on the tip. Then switch to the sad ball and allow for predictions and arguments. Then proceed with the reveal.

Things That Go "Bump" [Virtual Demonstration] at Teachers Pay Teachers

A new letter grade for the pandemic: E

It is impossible to characterize everyone's experience with teaching and learning during the COVID-19 pandemic spread throughout the world by the novel coronavirus. 

Many teachers are working with unprecedented intensity to craft synchronous and asynchronous instruction that will cover and deliver academic content in an engaging and suitably rigorous way.

But the products of all this time, talent, and energy are not being universally absorbed by the students in the black Zoom thumbnails with muted microphones. There are stories in each one of those blank frames, covering a broad array of situations.

Many of us seem to have students who are completely disengaged. They are on our rosters, but we never see them, they are not in our Zooms, and they do not turn in assignments or take assessments. They rapidly descend into grades that are in the single digits, perhaps up to about 20%. 

But there are some who seem to be somewhat engaged. But their participation is scattershot. They fall below 60%, but remain north of 40%. I am wondering if an F is the best grade for them while schools are wholly shut down or (worse), engaged in the pure partial daycare service that goes by the name of "hybrid".

So what about a grade of "E" for them? Not an "F" grade of fail. But not really a "D", either. "E" for evidence of engagement.

As a practical matter, the best I can do for now is to expand my range for a "D–".

One thing that a number of us are seeing more and more of in our parent-teacher conferences is parents and students who want to take an F for this semester so that they can repeat the course for a better grade next I'm not a fan of that practice. [Side note: Physics and Conceptual Physics are scheduled to be replaced by Physics of the Universe in my district next year, so that practice will be messy.]

I would let students move on with Es. Otherwise there will be a pandemic of students wanting to repeat courses when schools reopen in a meaningful way.

It's just an idea for now. But I wonder if it's an idea that will make more and more sense the deeper we get into the pandemic.

What do you think?