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05 September 2019

What do I do if I am teaching AP Physics but I don't know physics?

A teacher got switched from teaching chemistry, in which she is a subject matter expert, to teaching AP Physics 1, in which she is emphatically NOT expert.  She is well aware that students in high-level courses like this tend to be "students who care," and she fears also that such students "can tell when a teacher has no idea what they are doing."  This teacher is quite worried about the high-stakes of the AP Physics 1 exam; she feels behind already, like she can't give her students the education they deserve.  

On one hand, it is entirely unfair - to this teacher AND to her students - for the district to put them in this situation.  "Here, Greg, teach AP art and design!"  Yeah, right.  Not gonna go well.  

However, for all kinds of systemic reasons, an enormous number of science teachers are forced into this same situation every year.  I meet them in my summer institutes.  What advice can I give?  

Look... you can't fake physics.  Students do and will know that you're not an expert.  But, and this is important... THAT'S OKAY.  I've had plenty of teachers just like you in the APSIs that I run, and they do very well - as measured over a three year period.  

The suggestion is, be open and honest with your students that you are learning AP physics alongside them.  Do every assignment with them.  Put yourself in lab groups with them.  You can use my tests - and take them yourself, with the students.  Use the AP Classroom personal progress checks, just like the students do.  Don't be the authority figure, because students will rebel.  Instead, be the captain of their team.

Your goal this year should not be to know anything about physics now, or next week; but instead, to get a 5 on the AP Physics 1 exam in May, if you were allowed to take it.  :-)

Then, have a three year outlook.  That's how long it takes to become comfortable teaching AP Physics.  You are not doing your students a disservice - you're giving them the education they deserve, because they deserve an ally who will do whatever it takes to learn physics alongside them.  You have to learn sometime.  And if this year's class gets the less-than-perfect you, so what, because you have a long career ahead of you; if you have a couple of rough years followed by decades of hard-earned expertise, well, you're serving the next generation more than well.  

The students will respond to your humility, earnestness, and hard work.  Okay, well, MOST of them will.  That's okay, 'cause after 24 years I don't always get every student to respond to me.  I have to be like a football cornerback, who usually prevents touchdowns, who cares deeply about preventing touchdowns... but who has to be able to recover instantly when he gives one up.

Oh, and do make extensive use of the AP Physics 1 workbook, available through your course audit.  It's designed explicitly for people in your situation.  You have students (and yourself) working through that, you'll be pointed in the right direction.  I'd also say get the 5 Steps to a 5: AP Physics 1 book, but that'd be self-promotion and I don't do that, at least not very often.  :-)

Good luck... 

27 August 2019

Embracing chaos in the physics lab

I run week-long AP physics summer institutes, which are essentially classes on how to teach AP Physics 1.  In terms of expectations and attitudes, these institutes turn into a microcosm of my full-year classes for high school students.

My students - and the APSI participants - have been conditioned to believe that the spectrum of good and evil is contiguous with the spectrum of lawful to chaotic.  Problem is, learning is not linear; learning does not obey neat rules.  Many of my best students would not be labeled “lawful” in a role-playing game - they’d be neutral, or very often chaotic.

I totally understand that, in an elementary classroom, chaos simply must be tamed into order so as to avoid the Hobbesian State of Nature that would otherwise be, well, natural.  If it's done right, elementary education should be far more about establishing how to relate to one another in civil society as about serious academic content.  Just as with the rules of writing or musical composition, rules of school must be learned and internalized before they can be professionally broken.

But physics students are emphatically not in elementary school any more.  They know well the rules of appropriate class behaviour and relationships.  While it is certainly important for teachers to intentionally build a positive class culture, we absolutely do not need to use elementary school style rules.  

Nor do we need any "rules" at all.  

When an authority figure dictates to a teenager an externally-imposed rule, the teenager rebels.  Sometimes that rebellion is external, with derisive body language, passive-aggressive or even actually-aggressive speaking out.  Probably more often the rebellion is internal.  A teenager may have learned to present submissive body language and to control their tongue.  Yet, teenagers sneer in their heads, they make plans to break or test each rule, they convince themselves the rule doesn't apply to them, they know from experience that they won't actually be held accountable to the rule.*

*Just as often the teenagers simply didn't register the rule at all because they were thinking about sex when the rule was presented.


At my summer institutes, I begin by talking to the group from the front of the room using powerpoint slides.  Why?  Because that's what participants expect.  They'd be confused, uncertain, and in most cases angry if I began the week by saying "pick your favorite AP problem and set it up experimentally right here with no guidance or instruction from me, the guy you're paying to give guidance and instruction."

By the middle of the first day of an institute, I've moved on to quantitative demonstrations - still me talking from the front of the room, but using physical equipment to verify the predictions I make on the white board.

Then by day's end, I've stopped talking at the board altogether.  Everyone does a motion graph activity, in which they individually communicate their predictions about the motion represented by a graph.  They bring their predictions and justifications to the front of the room, where I either help them communicate their prediction better... or I check off their prediction, at which point they go to the back of the room to use a motion detector and cart to reproduce their assigned graph.

During this last activity, I don't move - I sit at a desk, talking to each participant in turn as they come to me in a line.  In front of me unfurls a scene that would make my second-grade teacher's head explode.  Participants talk to each other, they physically walk from one classmate to the next seeking suggestions, they drop equipment, they set up equipment in both right and wrong ways... and all the time, I sit there, making not even an attempt to control the chaos.

It's not about control.  It's about lawful chaos.

See, I don't believe in Hobbes*.  Left to their natural state, students certainly are chaotic, but they are not usually selfish.

* Using synecdoche here about Leviathan - not referencing Hobbes the Comic Tiger, whose existence and philosophy I wholeheartedly support.

I don't give the institute participants - nor my students - a list of rules, guidelines, or instructions for this activity*.  Nevertheless, goodness rules.  People help each other, both with the predictions and the experiments.  They discover naturally who has the same graphs to work on, and so "lab groups" form organically.

* The one "rule" that applies here and throughout everything my classes do is the "Five Foot Rule" - students may collaborate freely, but they must separate themselves by five feet before writing anything to be turned in.

In my classes that run in this manner, it's quite rare that I have to call out a student for being "off task."  My tolerance for chaos must be high, of course - I can't be a control freak.  Yes, it often happens that I hear students talking about the upcoming football game; yes, I can occasionally see a student check a text message.  I've got to hold my tongue.  I only say something when the conversation becomes more than a short break - and then I am extraordinarily careful to be polite and respectful.  "Hey, Mr. Jones, I'm coming to your game today, let's talk about it there, okay?"  I don't take a phone away unless students truly can't control themselves - and then I'm still as respectful as I can be.  (The one time years back when I got outwardly frustrated with a student on a cell phone, I severely damaged the relationship with him and at least one of his friends.  My frustration was justified - yet my reaction hurt the situation, it didn't help.)

How do students know what is appropriate or inappropriate if I don't go over rules and guidelines?  They know because they are human beings with 14-19 years of experience interacting with other human beings.

Look, I recognize that's a flippant answer.  If you're asking this question - which I know many readers are - it's not because you're incompetent or stupid.  It's because you're legitimately worried.  Probably you're worried in particular about that one student who thrives on negative attention from their peers and teachers.  What if they don't even pretend to do physics, but instead go from classmate to classmate causing distractions, deliberately sowing the seeds of churlish negativity?  And then, how do you defend yourself to an administrator when you ask the student to leave, but (s)he says with false sincerity, "I didn't know what to do! I didn't know it wasn't okay to talk about non-physics things, and teacher didn't give us any rules or guidelines!"?

That's a battle that many of us, unfortunately, will have to fight.  But rules won't help.

If your administrator is giving any credence whatsoever to such a disingenuous complaint, then this administrator isn't going to suddenly come down on your side if you can show them how the student violated subsection (b) of class rule 3.2i.

Find a way to deal with the one underminer.  Don't seek justice, seek peace - that is, you don't need disciplinary consequences for a pain-in-the-butt student, you just need to be able to separate them from the class when they're not engaging.

This way, the rest of the class won't be afraid to relax and have fun.  Fun is chaotic... and that's okay.

21 August 2019

I'm teaching a fall 2019 online course in physics/physics pedagogy

Hey, all... this is an ad, but an ad for something you or someone you know may be interested in.

I'll be teaching an online physics course on circuits through the Putnam-Westchester Industry & Science Teacher Alliance (PWISTA).  Check out the Science Teacher Mastery Program.  Each class in the program is equivalent to what would be a two-to-three week content unit in a first year college physics course, but aimed at students who are * physics teachers.

* or intend to become

Do you know someone who is familiar with physics, but needs guidance in physics pedagogy, needs to know how to help her or his students understand physics?  Or, do you know someone who is being asked to teach physics, but is primarily a biologist or chemist and thus needs some content support?  Either way, this course will be of use.

I'm offering just one class this fall: Circuits.

For each, you will get access to all of my topical course material, both when I teach at the high-school (Conceptual or Regents) level, and when I teach at the college (AP) level.  This includes the labs, problem sets, and quizzes that I assign.  I'll give you written guidance about how to use this material in your teaching, and for your own study.

Then, I will host five one-hour online sessions on Thursday nights this fall (see schedule below).  In each session, I'll spend the first half discussing practical pedagogy, just as I do in my workshops and on this blog.  In the second half, I'll discuss specific content, problem solving, and test preparation issues as requested - or, I'll improvise where the participants take me.

See, I'm more than happy to address individual needs.  For each class, I will be videoconferencing via google hangouts from my labThis means I can show live experiments.  And, as people have questions that stray beyond the circuits demos I had set up, we can improvise to talk about anything of interest to the folks who sign up.  Yes, we're going to learn about circuits... but I'm happy to discuss whatever is on your mind with regard to your physics classes.

Participants can get 15-hour CTLE certificates and/or university credit hours through Purchase College.  They can also get three graduate credits in science education through Manhattanville College - see the site for details about credits, certificates, and pricing.

You can see the full course description via this link.

If you have further questions, please contact me via email or twitter; or, contact Mark Langella, head of PWISTA, through their site.  Mark teaches the chemistry courses, and has been a College Board consultant for many years - he's the varsity, in case you know anyone who wants a similar program in chemistry.

Schedule for PWISTA Physics fall 2019:

The following are Thursday night classes.  I'll meet each night from 8:00-9:00.

Sep. 26
Oct. 10
Oct. 24
Nov. 7
Dec. 5
(Dec. 12 available as an alternative.)

09 August 2019

Product review: Vernier's Go Direct motion detector (and PASCO's similar product)

Way back in 2010, when I didn't even own a smartphone, I began to explore the use of phone/tablet apps for classroom use.  I wrote

I have little doubt that, five years down the line, Pasco and/or Vernier will have updated their data collection line such that the probes work wirelessly with the iPad or equivalent, and the LabPro or LabQuest will be unnecessary.  

They say, either predict the event OR predict the date - never both.  Then you'll always be right.  Within five years, Pasco had indeed made it possible (though not at all easy or cheap) to use their sparkvue app to view the output of their probes.  A couple of years ago the PASCO Smartcart revolutionized motion and force detection in the high school lab.  (I bought a bunch of these.  They're great.)

And finally, as of this summer, I'm seeing all the probes I regularly use available from Vernier and Pasco in a bluetooth version.  I've bought a bunch from Vernier; I've tried out both the PASCO and Vernier versions.  Today I'll focus on just one...

The Vernier Go Direct Sonic Motion Detector

My wife and sidekick, Burrito Girl, can't stand wires.  They look messy, they get tangled... she was amazingly thrilled eight years ago when I bought her a bluetooth keyboard for her computer.  She would love this motion detector.  If she cared about physics equipment, that is.  

It's extraordinarily compact, just a Borg Cube 2.5" on a side.  No wires.  One side - the business end - includes the power button and the sonic generator.  Two of the other faces have a threaded hole for a mounting screw.  And one face includes the microUSB for charging*

* or for connecting to a LabQuest, if you want to.  You don't have to.

There's no demand for a dedicated interface - no LabQuest, LabPro, ULI*, etc.  It sends its data via bluetooth to the smartphone or tablet.  And the app couldn't be simpler.  The "Graphical Analysis 4" app is free to download.  You open the app to connect the motion detector.  That takes three clicks.  The fourth click is to collect data.  That's it.  Even a 9th grader could figure it out without instruction - good thing, since I'm teaching 9th grade.  

* Now I'm really showing my age.  I used the Vernier ULI in my classroom back when Things Were Otherwise and the Moon was Different.  I even used the motion detector connected to an Apple IIgs when I was a student.  When I visited Vernier in Beaverton a few years ago, they showed me Dave Vernier's special space where he kept, in working order, every version of Vernier probes and interfaces they've ever made.  I nerded out a bit, showing the same enthusiasm as when my bachelor party walked through the Corridor of Star Trek Artifacts at the Las Vegas Hilton.  Is that Worf's actual bat'leth?  Is that the interface that used a serial port to connect to a PC?

By default, the detector collects for five seconds.  Here's a screenshot of a typical velocity-time collection.  (Switching to position or acceleration is a matter of just two obvious clicks!)  Of course, as is typical with a sonic detector, it missed a point early on - no cart in my classroom was actually moving 18 m/s, i.e. 40 mph or so.  The real motion was captured after about 1.5 s.

I have to teach students to recognize the physical unreasonability of this common graph; then, I have to show them how to zoom in such that they get the output that makes sense.  On a labquest, zooming requires highlighting the relevant part of the graph, followed by two not so obvious clicks.  Oh, and it requires that the touch screen actually works, which is about as likely as an American Airlines flight departing on time.*

* The similarity is striking - just like with AA, the labquest is somewhat likely to have minor maintenance issues, which are not complicated to solve, but no mechanics are available right this instant, so it'll probably have to wait until late tonight.  In the morning, either the labquest/airplane will be working fine, or a replacement will be trundled in.  Fat lot of good that does anyone right now, of course.

But on the app, highlighting and zooming is a breeze.  I use my finger on the phone touchscreen that always works; I hit the magnifying glass button; and voila, the relevant graph shows up - see the screenshot.  The app is so, so intuitive.  Click a point - the vertical axis value shows up.  That's all I care about for basic data collection.

Yes, the app can do far more.  The button in the bottom-left of the screenshot brings up an easy to navigate menu of further analysis options, including slopes and integrals and curve fits and interpolation - it even lets you add your own annotations.  This app contains very powerful tools, tools that can be used for my undergraduate-level research projects.  I rarely need its most powerful tools, though, so I'm glad that the app has simple and useful default settings.  

Now, PASCO makes a very similar product - a compact, bluetooth sonic motion detector.  It works well, too.  I prefer Vernier here not because PASCO is bad, but because the Graphical Analysis app is far more intuitive to me than the Sparkvue app.  You might have a different opinion.  Try them both.  

The good news is, the landscape of PASCO vs. Vernier has changed.  For decades, teachers have had to choose one sensor manufacturer or the other.  The $250 or so per lab station for a Labquest or Capstone interface, plus $100 per probe that only worked with its own interface, meant that the Vernier-Pasco choice was for richer, poorer, sickness and health, till death do us part or the warranty expires.  

No longer!  With the advent of the smartphone-as-interface, now we are able to pick and choose among the bluetooth probes and devices.  For example... PASCO beat Vernier to the punch by about a year with their wireless smartcart.  I bought a classroom set of these.  But now I'm buying Vernier motion detectors, photogates, and force probes - with no sunk costs.  The smartcarts still work great with the free sparkvue app.

The moral is, just buy whatever of these bluetooth probes you like, from whichever manufacturer.  You're not constrained by your past purchases; you're not locking in to your lab's future.  

30 July 2019

Setting up AP Physics 1 problems in lab: "Student on a Raft"

On the last day of my AP Summer Institutes I ask participants to spend time just playing in lab.  In particular, I ask everyone to set up something related to a published AP Physics 1 problem.  As a result of this activity - at and beyond my institute - you can see

* Which battery drains first? (Frank Prost, Tom Mellin) (2017)
* Energy vs. time for a cart on rough surface (Nadia Lara, Joey Konieczny) (2015)
* Bumpy Track (Zach Widbin) (2016)
* Waves on a vertical string (Walter Keeley) (2016)

A few weeks ago at TCU, Stephen McAliley wanted to set up the multiple choice problem about a student on a raft in a pool, from the official 2014 practice exam.  Summary: A student starts on the right end of a raft, and walks to the left end.  Which of several pictures correctly represents the location of the student and raft relative to the bottom of the pool?*

*I can't post the problem itself for lawyerly reasons.  But this is easily enough detail to understand the elegance of Stephen's experiment that you'll see below.

I think of this and similar problems as not about relative motion, but about center of mass behavior.  The center of mass obey's Newton's laws.  Since no net force acted on the student-raft system, its center of mass did not move.  Then the answer to the original multiple choice question is obvious by inspection.  

This seems like an easy enough problem to set up experimentally - fetch me a raft, a student, a pool, and a video camera.  Not so fast, my friend.  The raft's mass needs to be significant compared to the student's.  And while we have a swimming pool on campus, it's not anywhere close to my classroom.  Peter Bohacek has set it up*: if you have a subscription to Pivot Videos, take a look at "Boy on a surfboard".  

*Of course he has.  My niche is setting up classic physics problems scaled to equipment and space in my high school laboratory.  Peter's superpower is setting up classic physics problems at any scale he wants, with whatever equipment he can get his hands on, with high quality video that includes measuring tools.  Imagine I were writing high quality short stories; then Peter is creating the billion-dollar film, complete with epic action sequences and a score by John Williams.

In the video below, you'll see Stephen's elegant in-class tabletop setup.  The "student" is represented by the PASCO constant speed bulldozer.  The "raft" is a bin, underneath which are two PASCO carts on a track.  Friction between the track and the "raft" is minimal; the weights on top of the bulldozer ensure that the bulldozer doesn't slip on the bin.  To get the student to walk across the raft, Stephen turns on the bulldozer.  Watch:

In the original problem, the raft and student were of equal mass, so that the center of mass was located halfway between the student and the raft's center.  In Stephen's classroom version, the bulldozer and the bin/carts are certainly not of equal mass; and I don't know where the center of mass of the bulldozer is.  

The question I'd ask using this video or live setup, then, is "where's the center of mass of the carts-bin-bulldozer system?"  

29 July 2019

Preventing the slacker culture from taking hold in your class

Last fall I “shadowed” a senior through his class day. I wrote numerous pages about the experience for our school’s prefessional development app. (What really, Greg writing long-winded commentatry about teaching? Imagine that.)

Among other things, I reflected on how my school - like *every* school I’ve taught at or visited - has two distinct levels of student engagement. The difference between an honors class and a general class isn’t always just the rigor, or even the brainpower of the students; it’s also the intellectual engagement of students, their willingness to wrestle seriously with ideas to the best of their ability. 

A number of students over the years have hinted that the main reason they are happy taking solely honors classes is that they can avoid the less-serious students.  For example, one bright and engaged student was quite frustrated in our un-tracked 9th grade English and history, and not because his classmates were “dumb”, not at all.  He was frustrated because so many of them approached schoolwork as an exercise in minimization of effort, and thus poisoned all interactions among classmates.  I observed the same issue when I taught a required junior-senior physics class one year. And it happens on the athletic fields, too – every season we have teams or programs that are dumping grounds for those who not only don’t give a crap, but are actively perverse in their lack of crap-giving.  It is practically impossible for a serious student or athlete to have a positive experience once the slacker culture begins to prevail.

This is where toxic teachers complain regularly and publicly - in the faculty lounge, on twitter, in front of parents, even - about how kids these days don’t care, won’t listen, are bad down to their very soul. Well, that doesn’t help.  You talk about a teenager or group of teenagers behind their back, and they *will* find out - and then they will live down (or up!) to your prejudiced notion of them. It’s one thing to occasionally vent because you’re frustrated. It’s another entirely to make repeated sweeping generalizations or accusations about the quality of students’ personal character.

And yet... the slacker culture exists, and will persist if teachers don’t actively fight it. Yes, I know you don’t have the administrative support to dismiss every student who causes you a problem; I also know that even the best teachers with the best administrators usually don’t have all the support they’d like from above. But fight we must.

How have I fought the poisonous slacker students over the years? 

·        Attrition.  I make it more time consuming to disengage than to engage.  Once students give up the fight, once they see that *I’m* not giving up, once they see that neither their advisor nor their parents nor the academic dean is going to tell me to back off, they recalibrate their minimum effort.  Sometimes just enough, but they recalibrate.

·        Reputation.  Where students have taken my class by choice, they’ve generally known what to expect from me, and so they’ve pretty much cooperated from the get-go.  Once I successfully build a positive physics culture in one class, that culture became contagious over long time frames. Exceptions includes my first year at each school, and the year I returned to the upperclass AP section after a long absence. Those years were quite difficult and frustrating for me.

·         Avoidance.  I teach primarily 9th grade now, and 9th graders are poor rebels.  Honors students of any age, once I’ve establish my reputation, are usually pleased to focus and learn in a positive atmosphere.  Research students that I’ve hand picked are thrilled to work with me and my expertise – they very much appreciate my “trust but verify” approach.  

But the upperclass, required general physics class? Our department puts teachers where they can best succeed. The other physics teachers do better than I do with that class because they are more in tune with the non-serious student, and they all have better relationships with those folks, especially given their extracurricular work.  One teacher simply wasn’t particularly demanding of such students, and thus won cooperation with those few things he did demand. The other two have better instincts about how to be successfully demanding of typical general-level upperformers, just as I have better instincts in other situations. That’s more than okay, that’s awesome - different people with different talents make for a well-functioning department.

·         And finally, reasonable expectations. I'm careful never to assign work outside of class that could possibly be construed as busywork. I am respectful of students’ time - I don’t assign summer work, or work over breaks. I taper my class so that seniors have much less to do in the spring than in the fall. Students need to see that I’m never asking them to do something for the purpose of, in their perception, asserting my authority.
Does it all work? Never perfectly.  When a cadre of slackers persists, my job is to ignore them, to instead pay attention to the vast majority of students who appreciate my dedication and expertise.  Eventually, perhaps one of the slackers sees the light and joins the positive culture - in which case I welcome him, never ever shaming him with reminders of his previous intransigence.  Some never adapt; but they can’t spread their poison effectively, because their classmates don’t allow it to spread. Hopefully.  I have to fight this battle every year.  I have to have faith every August that the positive culture will prevail.  I’m usually rewarded.

13 July 2019

Inserting equations into google docs - Equatio

Holy moly!  I have spent ridiculous amounts of time over the years trying to write professional-looking equations in my physics assignments.  Or often, I've spent enormous amounts of time simply scanning bad-looking handwritten equations.  Participants in my Purchase College AP Summer Institute last week showed me a wonderful computer and tablet app that seems to be a boon directly out of the star that I wished upon.

Take a look at Equatio.  It says it's free for teachers - I had to sign in with my google account, then it downloaded quickly and without trouble.  (My google account is through my school - no clue whether this will work with an unaffiliated personal account.)  

Then I went into google docs, where this toolbar sat at the bottom of the screen.  The toolbar gave me a couple of helpful hints, but was otherwise unobtrusive.  I tried typing the equation for the period of a pendulum.  "T =" was typeset in italics without fuss.  Then I wrote "2pi", at which point a menu came up asking if I wanted a capital or lowercase pi.  But I didn't even have to click!  The top choice was the more common lowercase pi, so I just hit enter to insert the pi⁣ and move on.  

(Of course, I'm not using google docs right now - I'm in Blogger's "compose" window, where I don't have access to Equatio.  Nevertheless... I can copy and past the Equatio picture from docs into this window here.  As you can tell, the pi that I pasted is larger than I want.  But it's there!)

To get the square root symbol, I typed "root."  But I also typed "sqrt" to get the same thing!  And "sq" gives me a menu of options!  In other words, I don't have to remember arcane code, I don't have to click slowly through an enormous tableau of options... I just have to hint at the symbol I want, and lo, the symbol shows up.  Wow.

Typesetting the fraction was automatic - I typed "L/g" and I got a vertically set fraction with a horizontal fraction bar, all centered under the square root symbol.  Here's the final result:
T equals 2 pi the square root of L over g⁣
I suppose I could nitpick and complain that the L is too high, too close to the top of the square root symbol.  So what.  I inserted this equation in barely more time than it takes to type a standard English word.  And the copy-paste function worked into MS Word, into this post, wherever.

I've been told (though I haven't yet tried) that on a tablet it can do handwriting recognition - that is, write the equation above, and the typeset version will magically appear.  

Your tests, at least, should look professional.  I don't mind sending out an in-class or homework assignment with handwritten items, with fifth generation bad xeroxing, with unaligned graphics that I literally copied and pasted to a page by hand.  I won't do that for a test, though.  A professional looking test is taken more seriously by your students.  So I've gone to great lengths to get professional looking equations.  Equatio has shortened those lengths.  Yay.

30 June 2019

Schedule cumulative tests once a month, but NOT UNIT TESTS!

I'm thrilled that the College Board has created a brand new course and exam description for all AP physics courses.  Now it is abundantly clear how much material each topic contributes to the exam - that wasn't clear previously for AP Physics 1.  

Part and parcel with the revised CED, the College Board will now provide access to an electronic platform called "AP Classroom" with a vast test bank.  Teachers will be able to electronically assign  "personal progress checks" relating to each unit - these will consist of authentic multiple choice questions. Furthermore, I've been told that through AP classroom we can assign authentic free response items, organized by unit.  This is wonderful.

The new CED does encourage categorization by unit.  I know that's far more useful than previously, when the exam was organized by "big ideas" which overlapped multiple physics topics.  Teachers - and students - prefer to think sequentially.  Learning might be nonlinear, but time is certainly linear.  We need to decide what topics and problems to work on each day of class, each week, each month... Yes, we absolutely must scaffold our content such that the same topics reappear in multiple contexts throughout the year.  But we also have to start somewhere, and progress somewhere else.  Unit guides and "personal progress checks" are outstanding places to begin.

So how do you set up your tests (or in education language, your summative assessments)?  Do you test every unit?  Every two units?  Do you use the personal progress checks as unit tests?

No.  I don't suggest using "unit tests" at all.

I still recommend that you set test DATES far in advance.  Choose days that are unlikely to be interrupted by state championship meets, by regional honors band auditions, by the Ohio State-Michigan game, or by the first day of deer hunting season.  

Don't move these dates for anything other than the apocalypse.  These are not "unit tests"!  They are, simply, tests.  Just as the football team plays their scheduled game whether or not they've mastered the zone blitz, your class takes the scheduled test whether or not they're fully comfortable with Newton's Third Law.  Part of the whole point of the test - or the game - is to find out just how comfortable the students are with the material.

I recommend AGAINST advertising the topics of each test, or even stating the topics to yourself.  The first test will include, say, kinematics and dynamics, to the extent that your class has discussed each.  The second test will include kinematics and dynamics and, say, circular motion and gravitation and energy, to the extent that your class has discussed each.  The third test... well,  you get the idea.

A "unit test" is a signal that what came before can be forgotten.  A "unit test" encourages your students - and you - to either rush to get material on the test, or to postpone the test because you're not ready.  

Just schedule test dates.  Then put questions on each test that are cumulative until that point.  That way you're doing six to eight AP practice exams throughout the year.  That way you're demanding learning in context.  That way you've that much more incentive to scaffold.  That way our students have that much more incentive to correct each test, knowing that the material isn't going away.  (Just as the football team has considerable incentive to watch film.)  That way someone who is slow, who didn't really get kinematics or dynamics as it was presented, can show an understanding of that material later.

22 June 2019

Four suboptimal habits of experienced physics teachers

The great and terrible part of the tenth or twentieth year of a successful teacher's career is that, for the most part, major substantive accountability to others no longer is a part of their life.  Sure, they'll be observed, asked about goals, required to check off continuing education requirements.  Nevertheless, solid teachers who have lasted so long don't generally get replaced for less than malpractice. We face no competitive pressure - when has a school ever fired a good physics teacher merely to replace them with someone purported to be even better?  I mean, that's the life of a football coach in a nutshell, yet unheard of in the education world.

The truly best teachers are accountable to themselves.  They ask tough questions of themselves: not  just "are my students learning physics", because they are.  Tough questions include, "How could I make learning physics easier for my students?  How does my students' understanding stack up against that of students at other schools?  Can we attain a deeper or broader understanding of physics without adding more (or even while reducing) homework? What evidence do I have that my students enjoy my class - not every moment of every session, obviously, but in a broad sense?"

These are the questions that I ask myself in practically every day.  Just the fact that you're reading this means you're asking yourself these questions, too.  

I'm a different teacher now than I was five years ago, ten years ago, 25 years ago.  (Occasionally because I tried something that didn't work.)  Even if you realize that you've developed one of the subobtimal habits listed below, it's never too late to change.

Reminder to relatively new teachers: This post is not for today's you - it's for you in a decade.  In the first few years, just keeping afloat is a major achievement.  Make one or two substantial changes to your course each year - don't try to reinvent the wheel all at once.  Most importantly, don't give in to guilt trips, whether internally or externally imposed.  You are serving your students well, even if you'll do even better in a few years. Read a bunch of this blog's other posts... come back to this one some other time.  :-)


(1) Giving too much help, or helping too early.  We all care about our students... and so we are tempted to answer their frustrated questions, to show them the right path when they ask us for help.  DON'T!  Assign problems that you think are appropriately challenging the students, and then expect the students to meet the challenge you've laid out for them.  So much long-term physics angst - on the AP exam, in a college physics class - comes because students have come to rely on help from the friendly and dedicated physics teacher.  When that lifeline is suddenly taken away right when the stakes increase, frustration ensues.  Don't allow that frustration to become normalized, because that's exactly why so many adults say "I hated physics."  Instead, allow students to make mistakes, make them own and correct their small failures, such that they are experienced enough to power through adversity on their own.

(2) Spending an excessive amount of time on early topics (then either cutting or racing through later topics).  Since no one is going to fire the physics teacher, it becomes all too easy to stick to motion and force through most of the year.  After all, if you don't move on, no one will complain - not the top students who are earning high marks, not the bottom students who aren't really learning much but are still getting grades they need because they're not being asked to learn much.  Physics teaching is certainly not about minimizing complaints, though! If you're not spending significant time on force, motion, energy, and momentum - plus another one or two topics of your choice - it's hard to justify calling your class "physics" rather than "physical science" or "an introduction to force and motion."  

(3) Assuming grades are the primary student motivator; focusing on the transactional rewards of the course rather than intellectual rewards.  If you're discussing the quality of college a student is applying to, if you're emphasizing how important for college junior year grades are, if you're continually reminding seniors in the fall how colleges look at their grades... then you are also de-legitimizing your class for those who are already accepted to college.  I mean, why shouldn't they just take a nap every day during class once their acceptance letter arrives?  If the only reason to try hard is to earn college admission, then you should allow those who have already secured college admission to leave.  (Of course that's ridiculous hyperbole.  Model via your actions that physics is something to be learned for its own sake.  When a student asks how much an assignment counts toward the course grade, don't answer - instead ask back with a smile, "are you going to work harder or not depending on my reply?"  They'll stop asking.

(4) Focusing on a student's short-term rather than long-term performance.  Teenagers live in the moment - it's the teacher's job to help them learn to work toward goals that take a full year to realize.  Don't allow students to ignore regular physics practice in the expectation of cramming a week before the AP exam.  On the other hand, don't legitimize despair when they do poorly on the first test of the year - failure happens in the short term, and it's okay. You'll be shocked how easy it is to get your class in the mindset that mistakes are bound to happen, that no one is a Bad Girl or a Bad Boy just for getting a problem set wrong.  Once short-term failure is accepted as normal and even as useful, then long term success is in the works.  

I'm sure there are others... post a comment!

31 May 2019

Visualizing Gauss’s Law with Onions

Jen Kaelin is a longtime AP Physics reader.  Once when we were grading the same question, we competed to see how many hand turkeys we could find drawn on part (c)*.

* Not really, College Board Lawyers.  The competition was something I made up just now for humorous value.  The hand turkey was authentic, though.

The other night she told me about her frustration and then elation at her AP Physics C E&M class as they struggled to understand Gauss’s Law.  They simply couldn’t effectively visualize some Gaussian surfaces.

I’ve had good luck before bringing in physical items to help with more difficult visualizations in E&M.  My personal favorite* was the top of a sour cream container for visualizing magnetic flux. Know which way the magnetic field points, then place the sour cream top where the wire loop is.  This allows you to see, in three dimensions, whether the field lines penetrate the sour cream top, whether they point alongside the sour cream top and thus produce zero flux… or somewhere in between.  

* And my students’ favorite, as they walked into the exam and all told the proctor confidently and firmly, “Mr. Jacobs TOLD us all to bring these sour cream tops into the exam.  Yes, really. And the top to a butter container is acceptable too, he said, but not margarine because he hates margarine.”

I also used the sour cream top when the Gaussian surface required was the “pillbox”, as with a very large plane with two-dimensional charge distribution.  But a spherically symmetric charge distribution requires abstraction. I can show my class a sphere - a racquetball, e.g. - but they can’t open up the racquetball to see the charge distribution inside.

Unless you use an onion, like Jen did.

Jen brought in onions, peeling back layers to visualize how the volume and surface area get much smaller as the radius decreases.  She found plush onions online, and many of her students started carrying these around school. First as a joke, I’m sure, but the mnemonic stayed with them.  Jen finally felt comfortable with her class’s ability to use Gauss’s law under spherical symmetry.

You got a good physical manifestation of an abstract idea?  Post a comment…