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30 October 2018

This is not a political post. Fighting hatred is not politics.

I spoke in my school's chapel in March of 2017.  Here is what I said, along with an epilogue written today.

Why do I teach at Woodberry Forest?

I’m an outsider to Woodberry’s culture.  I’m neither black nor white; I’m not Christian, I’m not southern. 

I teach here because we care about character.  We don’t lie, cheat, or steal.  We live in a community where we are consciously kind to one another; where, even when I disagree strongly with my colleagues, I feel that I and my family are welcome here.  My job description is NOT just to raise AP physics scores; no, I’m directed to know, challenge, and love my students.  And I do that.  Sure, it may take three weeks for me to learn faces, to tell the difference between a Cooper and a Barker… but I figure it out. (I also know that it took you a lot more than three weeks to understand Newton’s second law… but I’ll forgive you if you’ll forgive me.)  I know you.  I do challenge you, as everyone who’s been in my class can attest.  And I love you, unconditionally.  I taught a large portion of the senior and sophomore class… ask them.  Ask them if I ever lost faith in them.  Ask them how I showed my love through my actions.

Nevertheless, I’m an outsider here.

My mom’s family was Syrian/Lebanese refugees in the 1920s.  My dad’s family were refugees from when eastern Europeans were killing Jews in the 1890s.

Dad was born in 1942 - only three months after Pearl Harbor - in California.  On a couple of occasions growing up I heard Dad say, “If the Nazis came again, this is who I’d trust to hide my family.”   I thought he was joking, using hyperbole.  In retrospect, I realize that he was deadly serious. 

He knew how a community could and did turn upon the outsider, the other.  Dad met Jewish refugees who came to America after the Holocaust.  He saw what had happened to the Japanese-Americans who were sent to America’s own version of concentration camps.  He always kept, in the back of his mind, a plan to take care of us if things were to turn ugly.

I see your faces… “Oh, no, I thought he was going to talk about physics, but instead he’s going to preach Democratic politics at us.”  Relax.  I’m not even a Democrat.  I’m not condemning anyone’s politics.  I have voted Republican.  I’m probably more economically conservative than you – you’d be shocked.  Cut taxes to reduce the size of government?  Watch me.  I don’t object to anyone’s rational position on the Affordable Care Act.  Or affirmative action.  Or any political hot button topic.  I’m a debate coach - I believe deeply in political discourse.  Argue with me, argue with your friends, argue with your teachers.  I hope you listen; I hope you occasionally change your mind under the weight of logical argument.  (If you’ve never changed your mind, you’ve been cheerleading, not arguing or discussing.)

I remember some classmates in high school who “joked” about my family.  Jeff wrote in my yearbook, while smiling, “I wish your relatives had died in the holocaust, Jew!”  He was harmless, I thought then, a friend who went too far.  My dad saw what Jeff wrote, and was deeply saddened and hurt.  To dad – to the guy who saw the aftermath of the horrors of 1940s Europe – Jeff’s words were setting the stage for a deeper hatred.  They were normalizing hate.

Hatred for others is not politics.

When a large segment of this school flies Trump flags months after the election, when some even hang confederate flags, when you joke about black or hispanic or Jewish or Muslim or female people as being stupid or un-American or less important than you… your actions suggest hate, not love.  And I, personally, feel hated.  And hurt, because my dedication and love for you has been reciprocated with venom.  

Please don’t be defensive right now.  Remember, I have nothing but love for you.  You didn’t intend this hatred and hurt.  I know none of you truly harbors any ill will toward me, or toward anyone in this community.  I know that, because I know you.  You’re just showing which political “team” you’re on, the same way you’d hang a Duke basketball or Alabama football flag.  

But politics are not sports.  

In a fierce sports rivalry, taunting and teasing and chest-thumping banter is not just okay, it’s expected. You’re supposed to remind Cincinnati Bengals fans like me about how we’ve never won the Super Bowl. You’re supposed to exaggerate your team’s chances, to make ridiculous excuses for your team’s failures. Skip Bayless has made a million-dollar career of not letting facts get in the way of a good sick burn.  And as much as the debate coach in me hates him, he earns his money.  

Skip and Stephen A have set the example for the sports arguments you all have.  And, so what. It’s sports.  We care deeply, then we move on with our lives.  

But losing a political fight often has real consequences for real people.

In the early 80s, air traffic controllers employed by the government went on strike for better working conditions. My dad was incensed - he was fiercely anti-union anyway, the strike was sorta illegal, and it majorly disrupted the travel necessary for his job.  Dad cheered at the television the night he found out that president Reagan had fired all the strikers and replaced them with non-union workers.

He carefully pointed out to me, though, that my friend’s dad Bill was an air traffic controller who had been fired.  Dad made sure I understood that one should never, ever deliberately pick political arguments. President Reagan’s action had hurt Bill deeply:  Bill became unemployed, facing an uncertain future for him and his family.  Reagan’s decision was the right one, Dad thought, but it still hurt Bill’s family, and Dad insisted that we be respectful of that hurt. I watched - on the one or two occasions when Bill ranted about Reagan, my Republican father listened politely, nodded… and let it go. Dad disagreed with Bill, but he still loved Bill.   

Politics is not sports. Politics has real consequences for real people.  You Falcons fans are sad, but fine, even after a devastating Super Bowl loss. The folks deported back to horrific war zones are not fine.  The Muslim Americans who face hostile catcalls from strangers, whose homes and places of worship have been vandalized… they’re not fine.  The hispanic families who are targets of suspicion and harassment from their neighbors and the police, despite being legal, tax paying citizens -- they are not fine.  

Real consequences for real people.  Folks who loudly proclaim themselves to be supporters of the current administration have burned down black churches, destroyed mosques, set upon a campaign of terror against Jewish Community Centers.  When confronted, the President of the United States and his cronies have refused to condemn such terror.

Now, I don’t see anyone here personally encouraging violence or harassment.  In taking a dispassionate political position, you might not have considered its effects on individual people, especially if you don’t personally know any of the people who would be affected by your argument.  “I have nothing against Mexicans or Syrians, and I certainly don’t support violence,” you say, “I just support enforcing the law.”

Well, I’ve heard that rhetoric before.  “Teenaged boys are so wild and unmanageable.  Let’s enforce the laws we have to keep them out of trouble.”  

Should we strictly enforce, say, the laws against underage possession of drugs, tobacco, alcohol?   You could go to jail for a long time if you have contraband on dorm.  No, it doesn’t matter if it was your roommate’s, you’re still responsible in your room. Oh, and pictures of your girlfriend on your phone -- those are possibly child pornography, punishable by even longer jail time and sex-offender registration for life.  Your parents aren’t necessarily safe, either, because if the phone is on their account, if they offered you a sip of champagne at Aunt Matilda’s wedding, they broke the law, too, and face jail time.

Imagine that an armed police task force showed up at the front gate of Woodberry, stating that they intend to search the dorms to discover all violators of these laws.  That ain’t so far fetched -- I’ve been on a college dorm when the police conducted a sting against some partiers next door.  It was scary, especially for Catherine, who now has a criminal record even though she was merely hauling her laundry when the cops showed up.  She was in the presence of underage drinking, and so she was hauled away.

How do you want our school administration to react to such a police operation?  Consider two extreme options.

“Well, we do want to see the laws enforced.  The dorms are up the hill.  Go get those bad hombres out of Woodberry Forest."  Judging by the results of the recent amnesty on Turner hall, there might not be a lot of hombres of any sort left here.

Or, the headmaster and the dean of students could meet the police task force at the gate, perhaps alongside the hunting club as they just happen to be making their way to the lake.  They could ask to see a signed search warrant; and when the police couldn’t produce one, they’d send the police away until they could.  The administrators could then send runners, Paul Revere style, warning of the impending sting.  And then teachers could video every action of a police officer on our campus, so that we can be sure that “enforcing the law” doesn’t turn into bullying, into destroying the lives of a bunch of scared teenagers.

Obviously there’s a middle ground between these two extremes.  But if it came down to just one of these two options, I sure hope we’d choose the second one.  The one where we would actively protect you, the students we pledge to know, challenge, and love.

Jesus healed the sick.  He did NOT say, “we have to be careful of contagious disease -- send those lepers back to Samaria or wherever they came from to keep us safe.”  

During the election last fall, a campaign post characterized the refugee and immigrant “problem” with the question: If I had a bowl of skittles and I told you three of them were poison, would you take a handful?  The expectation was that fear of terrorism would cause Americans to say no, I’d keep that bowl of skittles far away from me.

That’s not what I’d say.  I quote Eli Bosnick now:

Do these skittles represent human lives?

Like, is there a good chance, a really good chance, I would be saving someone from a war zone and probably their life it I took a skittle?

I would take the skittles.

I would GORGE myself on skittles.  I would take every single skittle I could find.  I would STUFF myself with skittles.  

And when I found the poison skittle and died I would make sure to leave behind a legacy of children and of friends who also took skittle after skittle until there were no skittles remaining in the bowl.  And each person who found the poison skittle we would weep for.  We would weep for their loss, for their sacrifice, and for the fact that they did not let themselves succumb to fear but made the world a better place by taking skittles.

Because the REAL question -- the one hiding behind a horrible little inaccurate, insensitive, dehumanizing candy metaphor -- is, IS MY LIFE MORE IMPORTANT THAN THOUSANDS UPON THOUSANDS OF MEN, WOMEN, AND TERRIFIED CHILDREN?

And what kind of person, what kind of Christian, would think the answer to that question is “yes”?

As a result of his blindness, Bartimaeus had been shunned by his neighbors, neighbors who (without modern medical knowledge) believed his blindness was a curse that would fall upon them if they weren’t careful. Jesus not only healed Bartimaeus; Jesus welcomed the outcast Bartimaeus once again into the wider community, despite people’s fears.  Jesus set a pretty great example.

Folks, none of you here intend to cause hurt to me, or to the many others on campus who feel like I do.  I know that, and I do not bear a grudge.  Forgiveness is a virtue.

Intentional or not, though, hurt has been caused.  And responsible people who inadvertently hurt others attempt to alleviate that hurt.  Here are two steps you can take.

Step 1: Acknowledge the hurt that your public political cheerleading has caused.  That doesn’t mean you should give up on your conservative politics, nor should you ever be ashamed of your rational political positions. It means, though: take down your flag, stop joking about hateful political policies, and stop making fun of “liberals.”  Instead, bend over backwards to show love and respect to those with whom you disagree.

Step 2: Speak out.  Say clearly to your friends, teachers, and neighbors, that you do not support hate, even if you (like I) do support lower taxes. Condemn those who commit racist acts with clear, direct language.  Call out those who make excuses for hate, even if they be your friends, your parents, or your congresspeople.  Actively seek ways to bridge social gaps with those who feel like outcasts, as Jesus reconciled Bartimaeus with his neighbors.  Do everything in your power to convince people like me -- people who are outsiders, people who are afraid -- that you still welcome us as EQUALS, both at Woodberry and in America.

Epilogue, October 2018:

The very positive news is, the Trump flags and the confederate flags have come down.  I still hear students spreading conspiracy theories, but I think and hope this is out of ignorance rather than hate.  Our small community has become much less outwardly hateful in the 1.5 years since I spoke in chapel.

However, I am more scared now than ever.  Last week the USA suffered three terrorist attacks in three days, all by American white nationalists, two of the three racially motivated.  Hatemongering continues unabated on Fox News and on social media platforms, which unfathomably refuse to take large-scale action to curb racist trolls and propaganda-spreading bots.  

It’s time to hold accountable not only those who commit hateful acts; not only those who spew hate online and on television; but also those who stand by and give tacit support to the hatemongers.  If you - yes, YOU, reading this - if you will not speak out against white nationalism, who will?  

24 October 2018

Positive work done on a gas, and the new Pretty Good Physics - Secure site

"Pretty Good Physics - Secure" is essentially a wiki for physics teachers.  It includes all sorts of files - old tests, lab activity sheets, quizzes, homework problems, whatever people have shared.  It also includes most publicly released AP materials.  The College Board is okay with that, because we are sharing teacher-to-teacher.  Gardner Friedlander and Paul Lulai do tremendous work managing the wiki, being sure that yes indeed everyone who accesses it is an actual physics teacher.

You can access the site here, and follow the directions to join.  (If you're a physics student, you must ask your teacher to join.  Gardner brings out the nuclear arsenal upon non teachers who request access.  And he does know some nuclear physics.  :-)  )

One of the new features of the wiki, since it migrated to google this summer, is that it's easy to subscribe to an email list for all members.  People can ask physics teaching questions of the community, and generally a response comes back within hours.  Don't worry, you don't have to subscribe to this list to access the wiki.  I like it, though, because it has provided a venue for some excellent discussions, it's helped a lot of relatively new teachers, and it has a positive vibe (unlike some other notorious teacher message boards).  One commenter mentioned that it's "just like the old days", presumably harkening back to USENET or stone tablets or something. 

Just yesterday, a participant asked for clarification about a problem in the 5 Steps to a 5: AP Physics 2 book.  Before I answer, a disclaimer - while I wrote the Physics 1 and Physics C versions of the 5 Steps series, I didn't write the Physics 2 book.  This is not my question.  I very much LIKE this question.

A teacher said he was "boggled" - great, great word choice there - with the sign convention for positive and negative work.  And in particular, what is up with the signs in the solution?  Why are there so many negative signs?  Aarrgh!  Boggled, indeed.

Much as I like this question, I would have written the answer very differently.  It's making this teacher and his students think about irrelevant mathematical details rather than concepts.

I prefer the simple and conceptual approach - work done ON a gas is considered positive, because work done ON the gas generally contributes to an increase in the gas's internal energy.  Compression is work done ON the gas.  In every case in the problem, the volume is compressed - therefore, each process represents positive W.

Then, the amount of work done is the area under the PV graph.  By inspection, the area under the D graph is greater than under E or F.  So more positive work done in the D process.  THAT'S IT!

18 October 2018

College credit and placement for AP Physics C - take the credit, not the placement!

I've been reading an excellent discussion about different schools' philosophies about what to teach as a second year high school physics class after AP Physics 1.  I strongly prefer AP Physics 2; others prefer AP Physics C, especially as taught in the sequence described here

AP 2 is my preference because of the deep conceptual nature of the course.  Calculus-based physics is easy - yes, truly, I mean EASY - for anyone who has a serious and deep understanding of the underlying concepts.  And the high school environment is better than the college environment to develop conceptual understanding.  We can do things college professors can't - we have smaller classes, a closer relationship with our students, the ability to do hands-on laboratory work integrated with the entire course rather than in isolated weekly sessions; and we have the AP exam as a motivating and evaluative tool.

Those teachers who prefer to follow AP 1 with AP C are not wrong.  Students find value in approaching mechanics and E&M with calculus, especially during their senior year when it's important that the latter half of the course is easy.  They are learning skills that will serve them well in college.

But I see too many teachers and administrators making choices about AP courses for the wrong reasons.  

Specifically, a lot of amateur (and professional) college counselors see the words "calculus" and "algebra" and assume that physics C must be the better and harder course.  That's not true.  AP Physics 1 and 2 are much harder, and better as an introduction to physics.  A student with high level skills at physics 1 can pass physics C mechanics even with little or further preparation; that might also be true for AP physics 2 and C-E&M, but I don't have evidence.  There's a reason that I and many other experienced physics teachers recommend that even a Physics C E&M course begin with months of algebra-based material before ever touching the calculus.

Then there's the "colleges don't give credit" argument, which includes two major fallacies.

Firstly, don't believe anything you hear about college credit and placement policies unless you're talking directly to the registrar.  I've heard so many counterfactual rumors that I'm tempted to get Snopes involved.  People conflate placement with credit; people conflate credit toward a major with credit toward general requirements; people conflate different colleges with one another; people who should know better conflate the four current exams with each other and with old Physics B.  Be skeptical.

But more importantly... your students should most likely not be accepting placement out of calculus-based introductory physics, even if such placement is offered.  Okay, I'm not talking about a student trying to graduate early for whatever reason, or a student who needs to reach a certain level of work quickly to get a physics minor on their transcript or something like that.  I'm talking about the typical four-year college student who is considering a major in the physical sciences, and who needs to take upper-level physics as part of their course of study.

I've had numerous students over the years get 5s on both sections of the AP Physics C exams.  These folks are invariably offered the chance to start in the 200-level physics sequence as a freshman - usually a waves/optics course followed by introductory quantum mechanics.  I've had some students accept that placement; I've had others demure, preferring to begin in the standard 100-level introductory sequence that's essentially a fast moving AP Physics C course.

The feedback has never varied: the students who began in the 200-level sequence as a freshman all say they wish they had taken the 100-level introduction instead.  And those who started with the 100-level introduction were very happy with their decision.  

Remember, the 200-level waves/optics/quantum sequence is heavily mathematical, using linear algebra and differential equations fluently.  Even students who are comfortable with the calculus in AP Physics C will get lost applying matrix mechanics and differential equations to physical situations - especially when those physical situations have become even more abstract, even more removed from the laboratory experience and intuition they developed in your high school class. 

Furthermore, it's a difficult adjustment for a first-semester freshman to jump right in with sophomore physics majors.  Many freshmen have to figure out, well, life in general: how to live with a roommate, how to do laundry, how to handle the independence suddenly thrust upon them.  Even the most diligent and dedicated students often take time before they are back in the academic groove.  Trying to figure out quantum mechanics and the calculus-based wave propagation equation at the same time?  Um, difficult.  Survivable, sure, but perhaps a bridge too far.

Yet, those who take the 100-level Physics C equivalent become class leaders.  They have all reported (at many different universities) that the class still challenges them; they're not repeating already-learned material in a boring way.  Instead these veterans make friends among their classmates as they help out, figuring out new complexities in the process.  The relationships they build, and the confidence they develop in their skills, serves them well as they progress into the upper level courses.

And if they are mentally absent for a few weeks because they partied too much, or because they are dealing with personal crises as they learn to live on their own?  Well, they can catch up, because they know from your excellent high school tutelage how to learn the same mechanics and E&M topics they're faced with.

01 October 2018

Nice free-fall data with a motion detector

On the second or third day of kinematics, after we've discussed position-time and velocity-time graphs, I introduce acceleration.  I start by handing out the four - yes, only four - facts about acceleration.  

(1) Acceleration tells how much an object’s speed changes in one second.

This is the fundamental definition, one we'll use again and again.  It leads to stating acceleration in units of m/s per second - that way, every time a student writes a numerical acceleration with units, that student is reinforcing in her or his mind the physical meaning of acceleration.

(2) When an object speeds up, its acceleration is in the direction of motion.  (3) When an object slows down, its acceleration is opposite the direction of motion.

These indicate the direction of acceleration in words students can understand.  Note that I don't use the words "negative" or "positive" anywhere!  Directions of acceleration and velocity are stated as left, right, up, down, north, south, etc.  The language used matters here.  Students may never, ever say "acceleration moves left."  Nor may they say "the object accelerates to the left."  They must state either fact (2) or (3), and conclude with "the object's acceleration is left." 

Some practice with a PASCO visual accelerometer helps here.  In the linked post, I'm using this tool to work on misconceptions about the direction of force and motion; but just stick this accelerometer on a cart on an incline, and you can have all sorts of conversations about the direction of an object's acceleration.  

(4) Objects in free fall gain or lose 10 m/s of speed every second

Once we understand facts (1) through (3), then (4) is just telling us about a special case in which we know the value of acceleration.  That's it.  Pedagogically, it's important not to treat free fall as a BIG DEAL.  Just give evidence that objects in free fall do, in fact, experience 10 m/s per second acceleration, and be done with it.

Since at this point my students are well familiar with velocity-time graphs, I like to show that the slope of a velocity-time graph will be 10 m/s per second for an object in free fall.  That's easier said than done.  Motion detectors generally have trouble getting good data above 20 data points per second, and classrooms aren't usually more than 2-3 meters high.  Even if you're dropping a full 3 m, that gives a fall time of only 0.77 s, and only about 15 data points for the detector.  Don't even talk to me about getting an object large enough and flat enough to reflect detector's sound waves consistently, but heavy enough such that air resistance can be ignored.

Oh.  But I found such an object.  Look at the picture. 

I stored a 15 pound medicine ball for a year in a cabinet.  One side flattened, as you see; and it doesn't unflatten easily.  Awesome.

So a student stood on a lab table holding a motion detector on the ceiling, pointed down.  A second student dropped the ball from 20 cm below the detector, with the flattened side pointing up.  I got the cleanest line on a velocity-time graph that I've ever gotten from a free fall experiment! I told the LabQuest to do a linear fit on just the straight segment, and voila... 10 m/s/s was the slope.