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24 November 2014

Are we in the happiness business?

I spent a decade fine-tuning my elective general physics course to present about one-third of the material on the AP Physics B exam, but to the same level as that exam.  Students consistently did fantastic work, earning the equivalent of high 5s on the authentic AP-style tests I gave.

Then one year the population for the general physics course changed.  We began enforcing the requirement that all students take physics.  Those who had entered as 10th or 11th graders -- that is, those who didn't take 9th grade conceptual physics -- took this general physics course as a graduation requirement, not as an elective.

During that school year, I taught the same way, and I noticed no difference in performance.  As always, everyone who put forth a credible effort earned a B- or better; better than 1/3 of the class got As, with an overall average in the B+ range.  I was quite pleased with the year's work.

On the year-end course evaluation, though, I discovered significant dissatisfaction with the course.  "You're way too intense."  "You yell too much."  "Relax and back off."  I certainly was insistent and demanding in that class, as I had been for a full ten years teaching that course.  I had previously gotten only the very occasional complaint about my approach, coupled with significant thank-yous for bringing students through a difficult subject. In this particular year, though, a message was delivered unto me -- Back off.

And so I did.  I changed my approach to general physics for this new population.  I lowered the course expectations, so that they matched the New York Regents exam rather than part of the AP exam.  I made a conscious effort to use a calmer demeanor... instead of "NO!  BOUX!  ACCELERATION IS CERTAINLY *NOT* ALWAYS IN THE DIRECTION OF AN OBJECT'S MOTION!" it was, "So, Mr. Jones, could you please recall and repeat the facts we know about the direction of an object's acceleration?"  I truly did "back off."  What were the results?

* Happier students.  Year-end evaluations were quite positive, with no hints of the complains about me and my intensity.

* Poorer grades.  Only 20% or so As, and a class average in the low B range.

A large segment of the class continued making fundamental errors long into the year.  Many were content getting Cs.  But the class and I got along famously, and I've done well with the general-level students on this model for years now.

One day I recounted this story to a veteran teacher whom I greatly respect.  He began to redden a bit as I described the changes I made.  He finally exploded:  "Greg, we're not in the happiness business," he said.  "We're here to teach students the way we think best, not the way they think best -- that's what we're paid for."  

While I see this veteran's point, and agree with it wholeheartedly, I think part of teaching "the way I think best" is to respond and adjust to reasonable feedback.  Just as different levels of baseball call for different strike zones,* different audiences of student need different things from their physics courses.  I'll push my AP students as hard as I can.  They signed up for the varsity course, and they have the option to leave it it becomes more than they can handle.  But the general folks... they don't have a choice about taking physics.  Now that we're really requiring all of these folks to take physics, I'd rather they take away an enjoyable experience in exchange for a bit less depth of coverage.  I'd rather they be happy with a C than bitter with a B+.  And for those who want the greater challenge, they know how to sign up for AP next year.  They chose the general course, and for now, that's what they're going to get.

* And if you think the zone should be the same for major leaguers as for 8th graders, I challenge you to sit through an 8th grade game in which batter after batter waits for the inevitable walk.  If the pitch is hittable, I'm calling the strike.  I've never gotten pushback with this approach at the 8th grade or JV level -- and that is sort of the point.

POSTSCRIPT:  Interestingly, I am once again teaching the honors course this year, but I have maintained, for the most part, my lower-key, backed off demeanor.  And I'm not satisfied with my students' performance.

I have a gaggle of honors-level alumni who have given the Intense Greg positive feedback, who have mentioned how well they've been served by my course.  So why would I change my approach?  Nearly universally, graduates laugh at me, saying "Oh, I knew better than to confuse velocity and acceleration, I didn't want to get BOUXed!"  They knew I cared about them, and that I would work my arse off to teach them college-level physics the best way I knew how, they knew that a BOUX was never personal... but they also knew that they'd better not confuse acceleration and velocity.  

The toughest skill in physics teaching is adjusting your approach to the level of student in front of you, especially when different levels show up in your classroom back-to-back.  Even now that I have a clear game plan for each level, I still have difficulty pitching my tone and material just right.
  


19 November 2014

Should I buy my students commercial AP Physics 1 or 2 review software? (NO.)

I'm regularly inundated with spam*  offering to sell me question banks for AP Physics.  And I'm regularly asked by physics teachers, "Should I buy these?  My students want as much AP Physics review as possible."  The answer is NO -- Don't waste your money.

* the electronic and paper version, but not the canned meat version

But why is it a waste to buy review materials?  I can go on and on, as I'm sure those of you who know me could attest.  Below are the major arguments.

Firstly, and most importantly:  Why the obsession with extracurricular "exam review"?  The AP Physics exam tests physics knowledge; presumably your class is teaching about physics all year long.  The process of reviewing for in-class tests and exams is utterly equivalent to reviewing for the AP exam.  I'm always amazed at how students beg for, and are willing to pay good money for, "SAT review" -- yet talk to those same students' English teachers, and find out how they haven't studied for a vocabulary quiz all year, and they didn't pay any kind of attention to the grammar and usage review that was intended to prepare them for the sentence completion section.  I don't recommend feeding the exam review obsession, at least not until I can work out how to profit mightily from it.  Just use every trick in your book to make your students take every problem set you assign seriously, and you'll be surprised how the need for "review" abates.  Maybe if we made the students pay $10 per graded assignment, they'd realize that the best AP Physics exam review is their AP Physics class...

Secondly, why pay for what is widely available for free?  Good physics questions, like pictures of naked people and cats, can be found online without difficulty.*  While quality can vary widely, you can find enough AP-style practice questions to satisfy even the most compulsive student.  

* Unless the Puritans at  your school block all the hardcore physics sites.  

Finally, let's talk about "quality."  Writing good physics questions is HARD.  Writing good physics questions that are in the style of the new AP Physics 1 and 2 exams is even harder.  Some people I know to be outstanding physics teachers and physicists nevertheless have trouble creating clear questions at an appropriate difficulty level.  And some of the worst sets of questions I've seen have been in commercially available AP prep books.  Just because you're paying doesn't mean that you're getting useful questions, let alone better questions that are available for free.

So  where do I get AP review questions for free, then?  Start with the College Board's AP Central site.  They've published half of an exam in the "Course Description," plus a smaller set of sample questions, plus a full practice test for those who have an AP Physics Course Audit account.  I'm told that they will, eventually, publish a set of questions from last year's AP Physics B exam that would be appropriate for the new courses.

Next, go to "Pretty Good Physics -- secure."  If you haven't signed up for an account with that site, do so right away.  You can then access the Big Amazing Resource.  Also, numerous teachers have posted their own activities and tests from which you can pull review exercises.  

Use the 5 Steps to a 5: AP Physics 1 book, which includes a full practice test; next year's edition will include a second practice test.  If you have a commercial textbook, look at some of their cumulative end-of-chapter exercises.  (Nick Giordano is on an AP Physics development committee, and Eugenia Etkina's work has been used extensively in College Board publications.  If you have a textbook by one of these authors, use questions from it as much as possible.)

For those who have been to my professional development, look through the CD I gave you.  Don't look exclusively at the AP Physics tests; some questions from Conceptual Physics or Regents Physics are perfectly good for AP Physics 1 and 2.  Some questions I used as problem sets or quizzes are good as test questions, or certainly as test review questions.  I'll continue to update that CD.  Come to one of my summer institutes in June, or to my free "Open Lab" in July, and everyone in attendance can share what they've created.

Or just pick a physics teacher you know and trust, and combine forces by sharing .  Point is, in the era of crowdsourcing and the internet, there's no need whatsoever for you to spend any money just for a question bank.  Don't buy a cow; milk is free.

13 November 2014

Why I make students graph data as they collect it

When I run a laboratory exercise, students are required to "graph as they go" -- that is, data are not written in a table for processing later, but are plotted directly and immediately on a graph.  The inevitable question, from students and fellow teachers, is why?  I mean, physics data don't go stale.  The graph is gonna look the same if it's plotted tomorrow.  What is the advantage to insisting on a live graph during the laboratory exercise? 

The most important advantage has to do with how students understand experiments. A data table just looks like a bunch of random numbers, both to students and to experienced physicists.  It's when the data is put on a graph that patterns can be seen and understood.  By graphing as they go, students develop for themselves an instinct about how much data is "enough," whether the full parameter space is covered, what further data is useful, etc.  

Science teachers are always talking about avoiding a cookbook mentality in the laboratory, in which students mindlessly follow directions trying desperately to get the "right" answer.  Well, here's one way to get students to connect intimately with their data -- as they see the graph develop, they think about and process how the data connects with the physical experiment.  They wonder whether the graph will end up straight or curved, they construct hypotheses in their heads which are borne out or not by the graph.  

The practical advantage of "graph as you go" is that students don't write down a bunch of numbers and assume they're done.  I get pushback if students have sat at their desks to construct a graph, then are told "ooh, let's get some further data in this region of the graph."  Aww, man, I thought we were finished.  I even put the track away.  Do we really have to get everything out again and do more?  Can we just do ONE more point, or do we have to do a lot?  Grrrr...

If all data is going on the graph right away, I can walk around the room and suggest right away how their data collection process is going.  Everyone expects and welcomes my input as part and parcel of the lab course.  Lab becomes about producing beautiful graphs, not about getting done and away from the annoying physics teacher.


03 November 2014

Direct Measurement Video assignment: Einstein Rides the Gravitron


I've discussed "Direct Measurement Videos" before, in the linked post.  These videos are wonderful, because instead of a presenting a sterile "imagine this situation" type of textbook problem, the situation doesn't have to be imagined -- it's right there on the video.

But what exactly do I do with these videos?  I've been asked that question a number of times.  Here is my AP Physics 1 class's assignment for Monday, verbatim:


In the video linked above, an Einstein doll on a rotating platform appears pinned to a wall, as shown in the screenshot.  As the platform slows its rotation rate, Einstein remains pinned in place until he eventually falls. 

You are to determine the maximum coefficient of static friction between Einstein and the wall.  Justify your answer thoroughly – this means you have to explain not only how you solved the problem, but how you obtained or estimated the necessary data from the video in order to solve the problem.  Start with a free body diagram of Einstein, obviously…

This worked out better than I could ever have imagined.  

See, I'm dealing with a number of students who are not appropriately connecting mathematics to physics.  They want to explain results without reference to equations; they want to do calculations (both in variables and in numbers) without any verbal explanations.  When they're asked to explain a calculation, they tend to explain the algebra ("I subtraced T from both sides to get T = Fnet +mg") rather than explaining where the equations come from, and where the values they need could come from.  These deficiencies are hardly unusual in an AP class; but I am struggling this year to bring my class into a real understanding of quantitative-qualitative translation.

This video assignment seemed to bring out my students' best.  Most of the class made the free body diagram, set the friction force equal to Einstein's weight, and set the normal force equal to mv2/r. They knew from practice that the speed v can be written as (2πr/T).  They used Ff/Fn to solve for the coefficient of friction.  They made a table of values to plug in, and got a reasonable coefficient.  Great.

But then something beautiful happened... virtually all my students, even the ones who had been struggling, wrote me crystal clear explanations to follow up on their mathematics.  They told me exactly what I told you in the previous paragraph -- sometimes in the very words I used.  They explained how many frames were in a revolution, and how they calculated the time for one revolution just before Einstein dropped.  (Or, how many frames were in a HALF revolution before the drop.)  They either explained that they estimated Einstein's mass, or that they noticed that his mass canceled out of the equations they derived.  They explained how the radius of curvature was determined from the video.  

In other words, they completed the most thorough quantitative-qualitative translation that they've done all year.  Somehow, my students have been unwilling or unable to describe the process behind a calculation from a textbook-style problem.  The video brought out the best in them.  Why?  I don't know.  But I like it.