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26 July 2017

Methods of in-class collaborative work: 421

This weekend I attended a workshop given by Kelly O'Shea and Danny Doucette.  They showed us their outstanding approach to lab practicals, which they assign as group tests.  

The discussion in the room at several points turned to balancing the group / individual dynamic in the classroom.  On one hand, physics is a collaborative endeavor. Cooperation and communication are skills which we must teach and assess.  On the other hand, we are teaching result-obsessed teenagers, who default to letting the (perceived) smart kids do all the work, probably while making fun of them behind their back.  

If we're going to encourage, let alone require, cooperative work in physics class, we must incentivize appropriate collaboration.  Remember, incentives can and should take forms other than mere grades.  Although others have found success in assigning a direct grade for the quality of participation in group work, I have not; I find students spend more time gaming the grade than actually collaborating.

My personal approach to encouraging effective collaboration is enforcement of the five foot rule.  As always, my way is not the only way.  Another workshop attendee -- I dearly wish I remember who -- mentioned an extraordinarily clever approach to evaluated group work, one that I'd like to try.

He called it the 421 method.  The laboratory exercise or problem to be solved is presented to the class, and then the class is divided randomly into groups of four.  Then, work proceeds in three stages, with clear time limits assigned to each.  (Yes, stages are numbered strangely.  You'll see.)

Stage 4: Discussion.  Each assigned group of four may discuss the problem together; but they may not write anything down.  No pen, no whiteboard, nothing.

Stage 2: Representation.  The groups are subdivided into pairs.  Each pair may communicate orally and using a whiteboard.  However, they may only write representations - no numbers or words.  This means they can use equations, free-body diagrams, energy bar charts, etc.  

Stage 1: Solution.  Now students separate to use pen and paper.  They are assigned to write a thorough response, including representations, numbers and words.  This is turned in for evaluation.

People in the workshop asked, do you evaluate the group work?  Thing is, by evaluating the individual solution in this case, you are evaluating the group work!  If the students were effectively working together, communicating clearly with one another, pooling their talents well, then necessarily the product should be that each individual student can communicate by him or her self.  The student who held back from the group, who didn't actively participate, won't have the benefit of the four folks working together.  

This method does require that you assign lab exercises or problems that are beyond the simplistic.  AP-level questions are good here, or a simpler version of Kelly's group test-style lab practicals could work in this style.  If the whole approach to the problem is immediately obvious to more than one or two students in your class, there's little incentive for high level students to converse in stages 1 or 2.

I'll need to experiment to figure out the precise level of difficulty for this approach.  Nevertheless, I love the idea.  Let me know if/how it works for you.

24 July 2017

Ask for an answer LAST

Greetings from the American Association of Physics Teachers meeting in Cincinnati.  The exhibit hall opened last night with self-serve all-you-can-eat Skyline chili.  I have ascended to my eternal reward.

Since I arrived, I've done a wee bit more than eat chili and tour Great American Ballpark.  Yesterday I attended the High School Teacher Camp, organized by Kelly O'Shea and Martha Lietz.  We spent the day talking shop, meeting colleagues from around the country.  The keynote address was from Kathy Harper, discussing student perceptions of "mistakes" in physics class and how to channel those perceptions in a positive direction.

I've got a *lot* of notes on my phone which will inspire future posts.  For now, I'm going to relay an idea from Martha about her revised approach to AP Physics 1 justification problems.

I've written before about issues teaching students to articulate their reasoning on semi-quantitative or conceptual questions.  In sum: English class, history class, geometry class, and Fox News have taught students to begin arguments by picking a conclusion; then, to construct quasi-logical arguments twisting evidence to support that result, truth be danged.  Students are not used to the idea of beginning with the logical evidence, and then dispassionately asking what conclusion should be drawn from that evidence.

Of course, getting students even to articulate a quasi-logical chain of evidence is a tough challenge in physics class.  Come on, teacher, you know the answer, (think I) know the answer, if I'm right why do I need to say any more?  To break this first barrier, Martha had been an advocate of the "Claim-Evidence-Reasoning" approach to justifications.  For each problem, she would give space for the student's claim, i.e. their answer; for the student to write evidence from the problem statement or experiment; and then for the student to link the evidence to the claim through verbal and mathematical reasoning.  She required every student to address every element on every problem set.  

And it worked, sort of - Martha's students were willing to articulate their reasoning using words and equations.  Great.

But it was obvious to Martha that many students were merely guessing at the right answer, then cherry-picking evidence and reasoning that could support that original guess.  I've seen this intellectual stubbornness as well.  I don't know why people's brains have so much trouble adapting knowledge to new evidence.  I just know that they do.  Once a student decides that the answer is choice C, it takes an actual invasion by the Red Army to convince him that maybe the evidence points to choice D instead.

So, Martha suggested... why not ask for an answer LAST?

She subverted the paradigm to Evidence-Reasoning-Conclusion.  After the problem statement comes space for students to write evidence: facts, equations, and information relevant to the situation.  Then comes space for the reasoning: use logical connections to explain where the evidence points.  And finally, at the end, the conclusion: that is, the answer.  

Because the answer comes last, because students are not asked to commit to a conclusion before examining the evidence, students actually, well, examine the evidence.  They stop contorting their logic into pretzels to prove themselves right, and they start doing physics like a physicist.  Martha no longer has to suggest that their answers might be more likely to be correct if they'd use physics.

How am I using this?  I intend to rewrite some of my problem sets, especially in conceptual physics, making just one small change.  Problems have previously looked like this:

[Problem statement blah blah blah]

Answer:____

Justification:









But I'm going to take a cue from Martha, and rewrite this way:

[Problem statement blah blah blah]

Justification:








                                                                                                                        Answer:___


Let me know what thoughts you have, including whether this approach does or doesn't work for you.



20 July 2017

Mail Time: Detailed questions about the test correction process, especially in AP.

 Reader Jessica has some questions about test corrections.

1. For in class tests, you give half credit back for each problem missed. However, sometimes you do corrections with extra questions students have to answer in order to get the credit (which I think is a really great idea). Do all students have to answer these correction questions, or just the ones that got it wrong to begin with?

Just the ones they got wrong to begin with.  Since I’ve started teaching AP Physics 1, I often just hand back a blank copy of the test with a card saying which ones they missed -- this prevents the "well, if I just change this word here, would I be right?"

Is this change due to the way the AP 1 free response questions are asked to begin with? 

Yes.  On the old AP Physics B exam I used to ask additional questions in the style of AP 1 -- the idea is, you can't just get the number your friend got as an answer, you have to write out an explanation.  But AP 1 already asks for explanations.  So there's no additional work required, usually.

2. Do you tell the students what the correct final answers are when you give back the tests? 

No.  For multiple choice, they talk to each other and figure it out quickly.  That's fine, though, 'cause they have to TALK to each other, which is part of the point.  For free response, they figure it out too, but it's a more complicated process.

3. Do you do corrections on fundamentals quizzes? 

Generally no, because we do so many quizzes, and because fundamentals questions are straight-up recall.  For the end of year "Big Butt" fundamentals quiz, yes, we do corrections.

4. For your exam corrections (which I'm assuming are like midterm and final?), you said that you treat corrections like a separate 100 point test that students lose points from if they don't answer the corrections questions correctly (that's a tongue twister). Do all students have to do all the corrections questions even if they didn't miss the points for that question on the original exam? 

No, just the ones they missed.

6. For AP style tests with both mc and free response questions, do you have student fill out the multiple choice corrections form, or do you also ask extra questions for those on corrections? 

They just do the mc correction form.  If we're working in class, I'll often ask a question orally to be sure they understand subtle points.  And I read the correction carefully, to make sure they're addressing any misconceptions appropriately.

7. can you please explain how this works with the flow of the class... is this right?

Day 1 - take test  (Time to correct it and makeups of course) 

Day 2 - give back original test and blank for correcting, they work together to start on corrections. Collect back originals after a set amount of time in class.  Finish corrections for hw? 

Day 3 - collect corrections? 

That's pretty much right.  The schedule can change depending on other goings-on; for example, if half the class is on a field trip, the other half may do corrections, and field trip people just catch up for homework.  I'm very strict about regular homework deadlines, but I've often quietly allowed students who have a lot of corrections to do to take an extra day.  The goal is to get corrections right at all costs.

12 July 2017

Teaching AP Physics C to those who've already taken AP Physics 1: Sequencing

AP Physics 1 is designed as a first-time physics course.  While I suspect the majority of the 170,000 students taking the exam are seniors, the course is perfectly appropriate for sophomores or juniors; I even teach one section of 9th graders, and they do quite well.

So, then, what do you do when these underclassmen want to take more physics in future years?

I highly recommend AP Physics 2.  A high school student who does well in both AP Physics 1 and 2 could not be better prepared for college physics courses.  The deep conceptual underpinning provided by AP 1 and AP 2 will make even a calculus-based college course straightforward.  

That said, I know a lot of folks are teaching the calculus-based AP Physics C as a second year course.  Fantastic.  But it seems like a difficult transition: Much of the mechanics portion of Physics C covers the very same concepts mastered in Physics 1, though there's a good bit of calculus overlaid on those concepts.  Other than circuits, students have had zero exposure to electricity and magnetism.

Sequence AP Physics C like this:

September and October: Do algebra-based electricity and magnetism exactly as covered on the old AP Physics B exam.  Emphasize conceptual understanding.

November through mid-January: Go through the Physics C mechanics curriculum, paying primary attention to the calculus applications.

Mid-January through March: Start from scratch with the Physics C - E&M curriculum, reviewing material from the fall in context, and adding calculus applications.

April: Put it all together.


Why this sequence?

Electricity and magnetism are some of the most abstract concepts covered in first-year physics.  They're quite a change from Physics 1, where virtually every problem can be set up easily and quantitatively in the laboratory.  It's worth spending a significant amount of time just defining and using the concepts of electric field, electric potential, capacitors, magnetic field, induced EMF.  Using calculus while these ideas are introduced adds an unnecessary distraction.  Don't start with integrals and derivatives, which are conceptually opaque even to some of the best-performing high school math students.  

Start with the concept of the electric field, and the relationship F = qE.   Get students thoroughly comfortable with the direction of an electric force and field, with putting an electric force on a free-body diagram.  Then deal with electric potential and PE = qV.  Get students relating the existence and direction of an electric force to the difference in electric potential, and using electrical potential energy in energy bar charts.  Introduce capacitors as devices that store charge (according to q = CV) and block current.  Consider electric fields and potentials produced by parallel plates and point charges.  

Go on to magnetic fields and forces, first teaching F = qvB and F = ILB and their associated right-hand rule.  Consider how a current can produce a magnetic field.  Finally, explain induced EMF, and how to find the magnitude and direction of an induced current in a wire.

This is all AP Physics B stuff.  You can find a wealth of released exam questions on these topics, both free response and multiple choice.  Use them.

In about November, you can move on to mechanics.  You're at a significant advantage by waiting this long to start true Physics C material.  A number of your students will be taking calculus concurrently.  I used to have to teach them how to evaluate basic integrals, while my colleagues in the math department cringed and gnashed their teeth.  It's likely, though, that by November calculus classes have begun teaching integration, at least conceptually.  Physics can follow and reinforce calculus class, rather than the other way around.  And since your students are so well versed in mechanics concepts from their Physics 1 experience, they can focus on how calculus serves as a language expressing those concepts.

(Waiting until November for mechanics also solves a political problem.  If you start with mechanics, you give the impression that Physics C will be nothing but boring review, more of the same stuff from the first-year course.  Then when you bring on the electricity, you'll face a rather hostile audience who's already settled into a cozy senior year routine.  Start with the tough new stuff while your seniors are fresh and motivated.)

Finally, when you come back to electricity and magnetism, those concepts have had time to percolate in your students' brains.  Physics isn't mastered the first time students see it; it's mastered after the same ideas are seen in multiple contexts.  The full-on Physics C E&M unit doubly reinforces previous work: students revisit the concepts of field, potential, etc. that you introduced in the fall, but they also revisit the calculus language that you introduced with the mechanics unit.

I haven't had the opportunity to teach this course.  However, I've heard good reviews from those who have followed the approach I describe.  Try it.  Let me know how it goes.

04 July 2017

5 Steps to a 5 AP Physics: so many choices... here's a rundown.

Okay, obviously this post is a bit of advertising, but I've been asked enough questions that it's worth posting.  In early August, the 2018 versions of the 5 Steps to a 5: AP Physics 1 book will be published.

And I do mean "versions," plural.  It's hard enough that the College Board offers four different current AP Physics exams.  To add to the confusion, there are five different physics books under McGraw-Hill's 5 Steps imprint.  I wrote three of them.  I'd recommend four of them to you and your students.  Here's a rundown.

5 Steps to a 5: AP Physics 1, 2018 edition - by Greg Jacobs
This is the updated version of the top-selling AP Physics prep book that's been in print since the 2015 edition.  It includes two practice tests, both written by me, with complete explanations for all questions.  In the 2018 edition I've updated the text and fixed some errors.  Most importantly, I've rewritten one of the "about the exam" chapters to include the fact sheet that I use in my own class, and that my students carry around like a bible.  

5 Steps to a 5: AP Physics 1, "For the Elite Student" 2018 edition - by Greg Jacobs
I didn't come up with this title - McGraw-Hill marketing did.  I highly recommend it for your classes, though, because it contains some special and new material.  Jeff Steele - an AP Physics reader, head of the Virginia Instructors of Physics - has written a third practice test.

Most importantly, Jeff and I collaborated on a new section called "5 Minutes to a 5."  This includes 180 questions in the vein of TIPERS, but aligned to the AP Physics 1 exam, and all doable in five minutes each.  Each question could easily be the basis for an AP Physics 1 free response item, identical in style and physics content to the authentic exam.  These items would make excellent parts of homework assignments, or quizzes, or in-class worksheets to be followed up with experiments.  

5 Steps to a 5: AP Physics C, 2018 edition - by Greg Jacobs
This has been revised and updated.  The most important revision is that I rewrote some of the free response items in the practice exam to reflect the more intense use of calculus that we've seen over the past years.  In general, this is substantially similar to previous editions.

5 Steps to a 5: AP Physics 2 - by Chris Bruhn - not by me, but I recommend
I reviewed several of Chris's chapters.  He knows his business.  Some of the material is adapted from the out of print 5 Steps Physics B book that I wrote.  But it's Chris's book, and it is excellent.

Do NOT buy 500 Questions to Know by Test Day.
This monstrosity is under the 5 Steps imprint, so people think I wrote it.  I did not.  It is terrible.  It includes an enormous number of computational questions not even good enough for the old physics B exam.  I'm disappointed that this book exists.  I never had anything to do with it, I didn't even know it was coming out.  To me it is shameful that people have bought it expecting the same quality that the other books provide.  

But do buy the other four books, and even 5 Steps to a 5: AP Physics B.  
The out-of-print Physics B book is fantastic as preparation for a typical undergraduate course.  I'm trying to get McGraw-Hill to rebrand this book as a college physics prep book, because I still have alumni asking for it.  

Other questions?  Ask in the comment section, or by email.