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28 September 2011

Parents' Night: Teach a Class!

Parents' night, but not at Woodberry Forest
(Actually a parental awareness class
 in India, via Wikimedia Commons)
This weekend is "Parents' Weekend" at Woodberry Forest.  Since we're a boarding school, the weekend is a Big Event, one of the two or three times when we encourage and expect as many parents as possible to be on campus.  The weekend begins Friday with football and soccer playing simultaneously, followed by a nice dinner in the dining hall.*  Then comes the key event:  Academic Mini Classes.

* The axiom at all colleges, which persists despite its clear falsehood, is that food services saves the prime rib for Parents' weekend, and puts out dog food the week before.  Thing is, we're having prime rib (and challah!) Wednesday night as part of a special Rosh Hashanah dinner.  I wonder what we'll have on Friday night... 

What we call "Academic Mini Classes" is generally referred to as "Open House" at day schools.  Parents go class-to-class through their son's schedule sitting at desks among peers just like the students do.  Each class lasts ten minutes.  What we do with those ten minutes can set a tone for the entire year of parent-teacher relationships.

I've heard numerous theories and advice about how to approach Open House.  Much depends on your personality, your pre-existing relationship with the parents, the size of your class, the number of expected attendees.  I'll merely tell you what I do, not what you should do.  

(I will tell you what you should NOT do:  Don't read the syllabus and discuss grading and attendance policies.  Doing so encourages the parents to help their kids game the system when the going gets tough; you want the parents supporting you, not giving their kids legal advice.  More importantly, just reading the syllabus is BORING.  If you need to communicate boring information, give everyone a handout to read later.)

During my ten precious minutes with the parents, I teach a class on a topic that we have recently covered.  In the honors section, we've just covered projectiles.  So, I bring out the moving cart that launches a ball straight up.  Just as I do in class, I ask, "Does the ball land in the cart, behind the cart, or in front of the cart?"  I make the parents write down their answer, then argue with a neighbor.  We do the experiment, and discuss the reason the ball lands in the cart in language that they all can understand.

In general physics, I bust out the motion detector and use the fan cart (with the fan turned off) to create a position-time graph.  I ask, what will the graph look like if I turn the fan on?  I make the parents write down their answer, then argue with a neighbor.  We do the experiment, and discuss the reason why the position-time graph is curved.

These parents think of physics class as old, balding man writing equations that no one can understand on the board.  That's not what good physics teaching looks like.  I need to open their minds to new possibilities in ten short minutes.  By doing live, qualitative demonstrations, I convince this audience that physics is worth knowing; by using everyday language to explain the phenomena we observe, I convince the audience that physics is know-able.  After that, the skeptical frowny faces of parents who are angry that Johnny got a 5/10 on a problem set turn to wide-eyed enthusiasm.

Now, you might have a different approach. Perhaps you show that momentum is conserved in Angry Birds.  Perhaps you use live video from an ipad 2 in order to find the speed of a parent pitching a tennis ball.  Whatever you do, I'm suggesting that you bring forth your best performance, using any necessary tools.  Make the parents wish they could sit in on your class; make them sad to have to leave to go to boring ol' English class.  The political capital you buy with a well-planned, enthusiastic performance will be worth a hundred thousand printed pages of class rules.

23 September 2011

The OJ Simpson Question: Magnitude and Direction of Accleration

Knowing what an acceleration vector means about motion is perhaps the biggest conceptual challenge in first semester physics.  No matter how many times I say "the direction of motion has nothing to do with the direction of acceleration," this misconception (among many others) remains.

I ask students to memorize:  

* Speeding up means acceleration is in the direction of motion.
* Slowing down means acceleration in the opposite direction of motion.

However, put these facts in the context of a velocity-time graph, or in the context of specific motion north and south, and heads explode.  And that's really all we can do -- ask about the meaning of acceleration in as many different contexts as possible until the class is sick of such questions.

In the first several kinematics assignments, I've displayed a position-time or velocity-time graph and asked for a description, in everyday language, of the represented motion.  In order to tease out the physical meaning of an acceleration vector, I switch up:  I present a description of motion, and ask students to make a velocity-time graph.

1.    In an alternate universe that still obeys our laws of physics, O.J. Simpson leaves a tollbooth in his white Bronco the morning after killing his wife.  Soon after, he sees a police officer flash his lights.  Hoping to get away, he slams the gas pedal to the floor, but then O.J. hits a concrete barrier and crashes.  (a) On the axes below, sketch a velocity-time graph of OJ’s motion.[1] 

[1] Sketch, according to the College Board’s course description, means to “draw a graph that illustrates key trends in a particular relationship, such as slope, curvature, intercept(s), or asymptote(s).  Numerical scaling or specific data points are not required in a sketch.”

Most of the class gets this essentially right on the first attempt; the rest get it after a quick conversation with a friend.  The real point of the problem comes next:

2. Describe in words the magnitude[1] and direction of O.J.’s acceleration as O.J. is leaving the tollbooth.
3. Describe in words the magnitude and direction of O.J.’s acceleration as O.J. is traveling along the road unmolested.
4. Describe in words the magnitude and direction of O.J.’s acceleration just after O.J. sees the officer.
5. Describe in words the magnitude and direction of O.J.’s acceleration while the Bronco slams into the wall.

[1] “Magnitude” in this context means, how much acceleration does OJ have?  Answer relative to his acceleration at other parts of his motion.  No numbers are required, though you are welcome to make calculations if you so desire.

I can tell almost immediately upon reading these responses who understands acceleration, and who does not.  The ones who truly don't get it come in for a consultation, where we work on these concepts.  How can I tell?

Well, the response I'm expecting to parts (c) and (d) refers explicitly to the v-t graph and/or to definitions that we've learned:  "(c) When OJ sees the officer, the slope of the v-t graph is positive (a frontslash), so the acceleration is forward.  The slope of the v-t graph is steeper than when OJ calmly sped up from the tollbooth, so the acceleration has a larger magnitude here.  (d) When OJ crashes, the slope of the v-t graph is much steeper than anywhere else; so the magnitude of the acceleration is highest of all parts of the motion.  OJ's acceleration is backwards, because the car is still moving forward, but is slowing down."

The most common mistake is to state the direction of MOTION rather than of acceleration:  "(c) When OJ sees the officer, he speeds up rapidly.  So his acceleration is moving forward.  (d) When OJ crashes, he bounces back off the wall, so his acceleration is moving backward."  Anytime a student says that the acceleration is "moving," I know that he is conflating acceleration and velocity, so the answer is marked wrong -- yes, verbal skills are part of physics.

A less common mistake is to think that the acceleration must change if velocity changes.  "(c) After OJ sees the officer, his acceleration must change rapidly, because the accelerator pedal is on the floor.  (d) When he crashes, OJ's acceleration changes from a high value to zero."  No, constant acceleration means speeding up or slowing down; this student thinks acceleration must change in order for speed to change.

I do get about half the class writing clear, concise, and specific explanations that refer to the v-t graph or to the definition of acceleration.  I will show a fellow student's good explanation to someone who's struggling, to show the difference in the style of prose.  I'm teaching writing as much as I'm teaching physics, sure.  But the time I spend now demanding clear writing pays off tremendously later in the year, when an AP-style free response test requires one-minute justifications.


P.S. Only about half of my class had ever heard of OJ Simpson.  That says something about pop culture in the post-internet era.  What it says, I have no idea.

20 September 2011

Where do I get constant-speed bulldozers for lab?

Georgian Mark DiBois asks:
One weird thing... I still can't find a small toy bulldozer to pull a mass across the table... Where do you get those?
Simple answer:  In the science supply houses you're looking for what's called a "constant speed vehicle."  Fool around on google and you can see the device pictured above, available from Frey, Fisher, and others for $25-30 each.  I *think* these can move forward or backward at the flip of a switch.

Better answer:  PASCO offers two levels of constant speed items.  In a rare event, PASCO undercuts the competition with their "constant speed buggy", pictured here.  These are $8 each.  They only move one direction, but they work just as well as the more expensive bulldozers.

Coolest answer:  If you have a few bucks lying around for luxury purchases, try out the PASCO "variable speed motorized cart" pictured here.  It lists at $159.  But it has a knob for adjusting speed, and has traction enough to climb reasonably steep ramps.

My personal solution:  I have two of the $25 bulldozers and ten of the $8 buggies.  (I like to have some of each because they move at different speeds.)  I use these for laboratory investigations.  I also have one of the fancy-pants variable speed carts, which I use exclusively for demonstrations, or even research problems where necessary.


19 September 2011

Two Bad Questions

Two Bad Mice ponder Two Bad Questions
As regular blog readers are aware, I'm adjusting my AP physics B course to cover only about 60% of the material in the AP curriculum, keeping a similar depth of sophistication in the coverage of each topic, but demanding even more verbal explanations and justifications.  Part of this process is to redesign my problem sets so that some kind of verbal justification is required every night.  (Details at this post and this one, too.)

Most of this month's problem sets I wrote while sitting at the Starbucks on the Pearl Street Mall in Boulder, Colorado.  I do highly recommend such a retreat for summer planning.  All I did was to copy the problems that I've used successfully for many years, adding explicit prompts such as "Explain why the tension is greater than the weight of the stoplight," or, "Describe, as to a non-physicist, how much force the string exerts by comparison to a force with which you are familiar.  Justify your comparison."  This approach has worked well.

However, I discovered -- too late -- a couple of minor mistakes that turned into ill-posed problems.  As a mea culpa to my students, and pour l'encouragement d'les autres, I present to you these questions that you should not ask.

1.  This one is based on an old Giancoli problem, but I copied it wrong:  
In the design of a supermarket, there are to be several ramps connecting different parts of the store.  Customers will have to push grocery carts along the ramps, as shown above.  A grocery cart has mass 30 kg; the coefficient of kinetic friction is m = 0.10. Determine the maximum angle of the ramp such that the customer will not have to exert a force in excess of 50 N.
Sounds like a great question... but, as my students pointed out to me, it requires either numerical analysis on a graphing calculator or maximizing a function using calculus in order to solve.  I promise the class that they will never have to use any math beyond algebra I and the definitions of the trig functions, so they were pretty confused.  

The original question that I should have transcribed correctly asks whether a 5 degree angle would be too steep, knowing that customers should not be asked to exert more than 50 N.  That's a straightforward problem mathematically, which allows the rest of the question to focus on a description of just how much force is 50 N, anyway.  And the whole point was to provide an easy, confidence boosting problem for the class, who is finally getting the hang of equilibrium.  Grr.

2. I just didn't think this one through at Starbucks:
A 150 N block sits on an inclined plane, as shown.  The coefficient of static friction between the block and incline is 0.30.  Calculate the angle of the incline and the force of friction on the block.
Simple enough so far... it's straightforward if you recognize that sin/cos = tan.  Since that's the one trig identity that shows up in introductory algebra-based physics, I use this problem sort of as a reminder to know that identity.  But then I screwed up:
Now imagine that the same 150 N block slides down the same plane at constant speed.  Is the force of friction greater than, less than, or equal to the value you calculated previously?
Well, this question requires understand extremely subtle issues about friction, far more subtle than the AP exam or I cares about.  The coefficient of static friction can take on any value up to a MAXIMUM of Ff/Fn.  The question as stated is confusing to students who have had ten days of physics.  On one hand, they see that equilibrium requires Ff and Fn to be mgsinθ and mgcosθ, respectively; so Ff should be unchanged with the same block on the same angled incline.  But they also understand that the coefficient of kinetic friction is less than the [maximum] coefficient of static friction.  So the friction force should be smaller.  Which is right?

The correct answer is, don't ask this question to begin with.  I don't care how cool the underlying physics is -- and really, static friction is pretty awesome when considered from an expert, dispassionate, and deeply intellectual perspective -- a justification question this early in the course without a definitively correct answer can spawn not just confusion but hopelessness.

Now, you might suggest that a college physics course can and should include problems at this level of difficulty.  The course you took back in college sure did, and everyone got it wrong, and we were better for it, right?  Well, no.  We're not teaching physics majors here, we're teaching high school students at the college level.  Their confidence is a fragile thing, and must be preciously guarded.  In the first week, I have already "torn down" a number of students who struggled for a week just to draw a free body diagram and understand what a normal force means.  I need to build back these students' confidence, show them that if they follow the  problem solving procedure I've described in class, they can and will do well.  But they don't see physics as "cool," they see it as "hard."  Let's first convince the class that physics is "doable," so that at the end of the year they will be ready for "cool."  

And, oh yeah, since I'm assigning rewritten problems, I'm going to write a solution to every problem set this year, starting now.  I can't make this kind of mistake again.  Mea culpa.


14 September 2011

AP-level Kinematics... In Just Two Weeks!

I got a nice note last night from New Yorker Scott Marzloff, who attended my AP Summer Institute at Manhattan College.  Scott noted that he started the year with equilibrium and torque using quantitative demonstrations, and that his approach was successful.  Awesome.  However, he asks:
I am getting ready to start kinematics and I am wondering how you get through all of 1-D kinimatics in what looks to be about 6 days?  I know I can get through 2-d projectiles in a week, but 1-D with graphs, equations, and freefall I have never come close to covering in less than three weeks.  Do you tie the equations in right away with motion diagrams and graphs?
Well, to be fair, it takes more like 8-9 class days to get through kinematics, including both one- and two- dimensions.  And, I'm not saying that every one of my guys is ready to take AP exam problems on day 9.  Nevertheless, I get through kinematics just that quickly, and we perform well above the national average on kinematics problems come May.

I begin with position-time graphs, demonstrating with a fan cart and Vernier motion detector.  We predict qualitatively what a couple of graphs should look like, show that the slope of an x-t graph is velocity, explain how to find displacement from the graph's axes.  On the second day I introduce velocity-time graphs.  Acceleration is defined as the slope of a v-t graph.  I take considerable time to get students arguing about how to use the fan cart to reproduce various straight v-t graphs.

Three hints about teaching motion graphs:

(1) Homework related to motion graphs is not purely quantitative.  With every graph, I require students to describe the motion represented in everyday language, without terms like "acceleration" or "negative."  For nearly a week, homework and quizzes hammer kinematics concepts rather than calculations.  One night's homework is a 21-question set of multiple choice questions about motion graphs, on which I require detailed explanations for any question they initially get wrong.  Make the class explain their thoughts in words.

(2) I don't (yet) stress over the difference between vector and scalar quantities.  Kinematics is confusing enough without the subtlety of distance vs. displacement, velocity vs. speed.  I use velocity and speed as synonyms on these first few days.  Heresy, you shout?  Perhaps, but it works.  Try it.

(3) In the same vein as (2), don't even discuss sidebars, no matter how interesting.  For example, curved v-t graphs simply don't exist during the two weeks of kinematics.  If a student asks about them, I explain that a huge set of moving objects produce straight v-t graphs, and that the things that don't have constant acceleration simply aren't relevant right now.  Other irrelevancies include a-t graphs, "jerk", anything involving calculus...

Graphs take at least half of my time teaching kinematics.  Why?  Because once we understand motion graphs conceptually, algebraic kinematics is straightforward.

I explain that all moving objects we consider will involve straight velocity-time graphs.  But we want to be able to make predictions without having an actual motion graph in front of us.  How can we do that?  By using a straight v-t graph to derive some algebraic formulas.  I show that taking the slope of a straight v-t graph produces the first of the constant-acceleration kinematics equations.  I show that taking the area under the v-t graph, along with some algebraic substitution, produces the second of the constant-acceleration kinematics equations.  (I simply state the third equation, without derivation -- they get the point.)

I do a set of quantitative demonstrations with the PASCO projectile launcher.  In each problem, we define a positive direction, and fill out a chart in which we identify the five basic kinematics variables (vo, vf, Δx, a, t). We learn that the problem is solvable as long as we know three of the five variables.  I don't spend any time on algebraic methods -- they figure out the most efficient algebraic techniques on their own by doing homework problems.  (Exception: I do one example in which I demonstrate that we do not ever need the quadratic formula.  There's always a simpler approach.)

At this point, one-dimensional algebraic kinematics problems become simple for the majority of students.  Free-fall doesn't need a separate unit, like most books give it; free fall is just accelerated motion where a = 10 m/s2, down. We very, very quickly move on to projectiles.  Projectiles become simple, as well, once we learn to make two kinematics charts, one vertical, one horizontal.  Horizontal acceleration is always zero; time is always the link between the charts.  Since I taught equilibrium and free body diagrams first, no one is flummoxed when I show how to deal with an angled initial velocity using sines and cosines.  Projectile motion becomes more a reinforcement and solidification of kinematics concepts rather than a truly new unit.

That's it.

Most of the class is reasonably skilled, at this point, but they still need considerable practice.  But I don't give that practice in isolation.  Rather, the practice is integrated into our next few topics.  For example, next is Newton's second law.  Most problems require both a free body analysis AND a kinematics approach.  Well, when they have to use an acceleration they calculated from Fnet = ma to find how far an airplane goes on takeoff, they're practicing their kinematics skills.  Later, when two blocks collide at the edge of a cliff, conservation of momentum yields a projectile problem.  Practice in context is always more effective than rote practice.  (So, when did you really, truly learn to evaluate integrals quickly and accurately:  in your first three calculus courses where you were given explicit practice, or in your differential equations course, which took integration skills for granted in order to do more involved problem solving?)

Try moving along quickly in your simpler topics, so that either (a) you can cover more topics in the year, or (b) you can spend more time on the truly difficult topics later in the year.


10 September 2011

iPad Apps and Physics Teaching -- 2011 Followup

I’ve been using a school iPad since July of 2010.  I spent a good deal of time in the summer of 2010 searching through the app store for things I could use in physics.  Generally, I found that the apps specifically branded for “education” were not of significant use.  Most were silly, or available for free online (rather than for $1.99 from the app store).  However, some apps that were NOT specifically designed for education were enormously useful, and I have used or will use them in class:
·         The magnetic field sensor with 3-d compass and output reading in microTesla
·         The “clinometer” angle indicator
·         “Star Walk” astronomy program, which is a portable and dynamic version of what “Starry Night” does.
I wrote a blog post last year about  the potential of the iPad in physics.  This is the second-most-viewed post on my blog.  I have had three personal emails asking for an update – what have I found out since last summer?

The answer is, I haven’t had the time to find new apps on the iPad since last August.  I know that the pace of the mobile app technology has been furious.  For example, the iPad 2 can take videos, and instantly import those videos into the logger pro software that we use to make position-time graphs.  That app would cut a 1-hour lab to 15 minutes.  My students found an app that uses the speaker to create a known frequency, essentially replacing my frequency generator.  I have heard of other good physics apps, but I have not begun using anything else myself.

Aside from the apps in class, I’ve found two other unforeseen but critically important uses of the iPad. 

When I am broadcasting football and baseball, I have instant access to the internet and to my email.  Thus, I can report in real time on scores of other games (both professional games and Woodberry games).  I have received in-game messages from listeners in order to better tailor the broadcast to their needs.  At this point I have a hard time imagining a broadcast without the iPad at my side.  And I haven’t even thought about electronic scoring and statistical software, which (as of last summer) is not yet at the point where I’m ready to use it, but should develop to a useful point in the near future. 

As the debate team coach, I used the iPad incessantly.  Students did research on the bus on the way to tournaments, looking up facts to back up last-minute arguments.  After a round, students would report on new arguments they had heard; I would give them the iPad and advice about what to look up to counter the unforeseen argument.  As a judge, I used the iPad to time the speeches – the advantage of the iPad over a stopwatch was that I could keep the timer running but flip the screen to google to look up disputed facts when necessary.  [In one round, both sides disputed interpretations of the constitution.  In no more than a minute, I had found the text of the 2nd and 26th amendments, to find out that BOTH sides had made devious misquotations.]  And, it became nearly traditional that after the awards ceremonies, I would use the maps function on the iPad to find locations for meals that were on the way home but which provided exciting and different options.  It was most useful to be able to show definitively that there was NOT a Chuck-E-Cheese within 30 minutes of Broad Run High School.  And thank goodness.  J

Is there a point to providing iPads for student use?  Not right now.  The arguments for or against iPad use for students remind me of the discussions 10 years ago about laptops.  Some schools provided each student a laptop, provided network hookups at each student desk, and pressured teachers to use the laptops as an integral and indispensible part of their classes.  Sounds great in principle.  But: 
(a)    The laptops themselves were obsolete within a couple of years.
(b)   Even the network infrastructure was obsolete quickly.
(c)    Only a very few teachers had authentic use for the laptops.  The vast majority of academic laptop “use” in class was done at the pointed request of administrators, and consisted of activities of questionable value.  While I would never support the old-timey Luddites who would ban the internet from our students’ lives, I would nevertheless suggest that a teacher who does not WANT to embrace new technologies can not be effectively forced to do so.  True progress in academic technology comes from having technology available for those who truly desire to use it.
(d)   The easy access to the entertainment aspects of the laptops in class caused a problem that generally outweighed the benefits of the educational aspects. 

Replace the word “laptop” with “iPad,” and I’ll bet one could write the same four statements in a decade.  (Furthermore, I read an article noting that the “revolution” of educational television in the 1970s and of classroom computers in the 1980s had precise parallels to the laptop explosion in the 2000s.  The four points above pretty much could be said about educational television and video (remember laser disks?)  when those technologies first came out.)

Now, I have found good use for a class set of mobile app technology.  When I had a free app that did something useful – like the angle measurer or the magnetic field probe – I encouraged students with ipones or ipod touches or ipads to bring them to class.  The students were most comfortable downloading and using the apps on their own, and enjoyed the “coolness” of the device far more than they enjoy my standard equipment.  The fact that the app was on a device with which they were already familiar broke down the barrier of “I don’t know how this works, I’m frustrated!” in the laboratory.  That sentiment is not to be underestimated.  But there’s not enough of this sort of thing to justify $600 per student for an iPad.  I found that enough of our students already had a compatible device so that I could run the laboratory activity.

The iPad specifically is the only device I’ve seen on which a digital textbook would truly replace a paper text.  Its screen is big enough, its processing quick enough, its display is full color, fully zoomable, and annotations could be done with a finger.  The textbooks are not available yet, I don’t believe.  But when they are, it would be extremely convenient for a student to carry the iPad rather than a stack of books.  I already have been using the iPad as my library as I travel.  I have a personal “nook” which I have synched with the iPad.  When I travel, I can access all of my electronic books instantly through the nook app; in fact, Shari and I can BOTH access our electronic library, since I can use the iPad and she can use the nook.  (Plus, I can buy a book instantly without going to a bookstore.  Plus, I can subscribe to and read a newspaper while traveling.  How awesome would THAT be for boarding school students?)

For now, though, the pace of the technology is changing so rapidly that I don’t think it useful to make any long term decisions about mobile devices.  Let’s see the future of android devices.  Let’s see whether the price of electronic books goes up or down.  Let’s see whether textbooks become more widely available in digital format. 

Greg Jacobs

07 September 2011

Supplement Review: The AP Prep Book for Walker Fourth Edition

Every summer at my AP Summer Institutes I'm asked, "Which is the best textbook?"  And I answer, "None of them is good, none of them is terrible, and they're all essentially the same."

Publishers know this.  One way they try to differentiate themselves in the marketplace is through supplementary materials.  The online resources are usually a boondoggle -- you don't need to pay for physics materials online.

But I'm seeing increasingly strong AP-specific supplements.  Publishers seem to be getting the message that you can't just hire a hack freelance writer with a physics degree to write good test questions for a college-level physics course.  Nor can you hire a random physics professor, nor a graduate student.  AP readers and exam authors are the experts who should be tapped.

Cutnell and Johnson jumped the gun years ago by getting Hugh Henderson, an AP reader and former member of the test development committee, to write their AP supplement.  (Note that this is a 2003 edition... the newer edition does not have Hugh's name on it, and I have not read it.)  Hugh included three AP physics B tests; I still use questions from these on my in-class tests.

This year, Serway got into the good-AP-supplement business.  They hired a long list of very strong AP readers, including exam leader Shelly Strand and former exam leader Bill Pappas.  (I won't review Serway's material because I contributed numerous free response items.)

The book that has caught my eye is the supplement to the James S. Walker text from Pearson, pictured at the top of the post.  It's written by Connie Wells, a former member of the AP development committee, my table leader at the AP reading in 2001, and an all-around expert physics teacher.

My first, raw test of an AP prep book is to leaf through and look at topics.  A depressing majority can be immediately defenestrated because they include improper topics, like calorimetry, rotational dynamics, or relativity.  Others can be burned at the stake for including multiple choice questions that obviously require calculators.  Connie's book passes this first test.  She includes review of rotational kinematics and dynamics, because she seems to be tasked to parallel the chapters in the Walker text; however, she is crystal clear that these topics are NOT COVERED on the AP physics B syllabus.  

Every problem that I looked at was right on-level for AP.  She included some simple calculations in the multiple choice, sure, but the majority of her questions require serious conceptual application -- just like on the real AP exam.  Solutions (not just answers) are included.  

I was most pleased that I found laboratory-based free response questions.  Connie was on the development committee while AP was still transitioning from the days of "shut up and calculate" to the current emphasis on verbal expression of conceptual understanding.  She was the primary author of perhaps my all-time favorite AP physics B question, the one about the platinum resistor.  (I can't post it here because I can't find a legit copy online; but look up 2001 problem 5.)  Sure enough, Connie's book includes questions testing lab skills and concepts, including graphical analysis of experimental data.  

I could not recommend this supplement more highly for teachers of AP or honors-level physics.  In my new Honors Physics I course, which is intended to anticipate the College Board's future AP Physics I course, I need to create a whole host of tests and quizzes with new multiple choice items.  Connie's book will be one of my go-to sources.

04 September 2011

Should you assign seats?

Should you assign seats in a high school physics class?  The theoretical arguments could go either way, with fundamental principles of teaching contradicting themselves.

Rule 1 of teaching high school:  Never condescend, or give the appearance of condescending, to your students.  If anything you do in class might possibly be phrased in a singsong voice that begins "Now boys and girls," you're screwed.  Fair or not, students are almost looking for an excuse to act disrespected -- they are quick to feel like they're being treated like babies.  A seating chart seems like it should fall under this proscription.

Rule 2 of teaching high school:  Trust, but verify.  We all know that it is in our students' best interest to do homework, and we want to trust them to be self motivated to do their homework; but we nevertheless collect the homework, at least if we want it done right.  Suggesting that students read their text has a very different effect from "Tomorrow there will be a reading quiz on chapter 2.3, on which you may use your reading notes."  The method of verification can vary, and certainly does not have to be grade-based.  But, veterans know that any rule, suggestion, or good idea that's not backed up by some sort of verification is ignored.  

Along those lines, a junior or senior in high school has been told many times that it is a good idea to sit at the front, not the back, of the room.  It's a good idea to sit away from those who might distract them.  It's a good idea to sit next to people who aren't necessarily best friends, to promote focus during lecture and to possibly create new friendships through the shared experience in physics class.

So, if you don't assign seats, what happens?  The back rows fill up first, and friends (or couples or wannabe couples) huddle together.  And no one changes seats after day one.  

When it comes to assigned seating, I think rule 2 trumps rule 1.  I've assigned seats only twice in my sixteen year career... but now I wonder why I went so long without assigning seats.  I use "check your neighbor" questions often in class.  Now that everyone's "neighbor" may or may not be a good friend, the discussions are more physics-focused, and less likely to devolve into a discussion of weekend plans.  I insist on regular collaboration amongst the class.  Once everyone has been forced to discuss physics in class with a random classmate, they become more comfortable collaborating with that classmate outside of class, too.  And though I've rarely had major problems with classroom management, I find behavior to be even less problematic when seats are assigned.

In order to avoid the appearance of using elementary school methods on the first day of class, I present assigned seats as a fait accompli.  I certainly do NOT allow folks to sit down anywhere, only to move them to an official seat a few minutes later.  No, I've prepared folded index cards with each student's name on them.  When a student arrives on the first day, he finds the seat with his name on it.  End of story -- no discussion, no argument, partly because no one realizes that an argument might exist.  

I've found it especially effective to switch up seating a couple times a year.  I re-distribute seats quasi-randomly in the second trimester, and again in the third.  So, when a student complains (whether disingenuously or not) that his assigned seat is not conducive to learning, I point out that the seats were assigned randomly, and that they will change in a couple of months.  If someone does have a particularly annoying seat, like in the back corner of the room or next to an obnoxious person, then I'll be very sure he gets a prime ticket next trimester.