Buy that special someone an AP Physics prep book: 5 Steps to a 5: AP Physics 1

Visit Burrito Girl's handmade ceramics shop, The Muddy Rabbit: Yarn bowls, tea sets, dinner ware...

27 June 2015

Get class started right away -- no silly questions, no individual discussions

So many physics teachers would like more contact time with their students.  Sounds great, but don't count on administrative fiat giving you exactly the schedule you want anytime soon.  You don't make scheduling decisions, and be glad you don't, because everyone is somehow unhappy with every academic schedule ever devised.

The best solution to a schedule you don't like is to make the most of every moment you are allotted.  Don't stop physics work ten minutes early because you finished your planned activity -- instead, have a TIPERS or some sort of check-your-neighbor activity ready for just such an occasion.  Start class when the bell rings, not when everyone has finished their conversations and meandered to their seats.

Starting class promptly is a tricky exercise.  You don't want to be the officious arse who metes out punishment by caning* to those who show up a moment late.  But without careful attention to the start of class, human nature means that you'll be getting down to business later and later as the year moves along.

* figuratively.  I hope.

Routine is your friend.  My personal preference is a two-to-four-minute quiz to start every class.  Not only does the quiz provide a better review than any amount of me talking at the class, the act of me saying "begin the quiz" and starting the countdown timer sends the message that class has started.  No nagging, whining, begging, lecturing, or caning is ever necessary on my part.  Because this opening quiz is an immutable routine, students adapt without complaint or comment.  When someone is slightly late, there's no discussion or excuse, because the latecomer races to get as much of the quiz done as possible.

But there's more to starting class on time than beginning the quiz.  As students enter the room, you'll often hear a cacophony worthy of an elephant seal rookery.  "Mr. Lipshutz, did you grade last night's problems?  Can you help me with this solution?  Did we have homework?  What are we doing in class today?"  

Aarrgh!  I don't want to be unfriendly, but (a) I want to start on time, and (b) I don't want to encourage dumb questions by answering them.   And most any attempt to address a silly question at face value does in fact beget more of the same.  If I graded the homework, it will be in your work-return box, just like it was every other day this year.  I would be happy to help you with solutions, but not two minutes before class time, as we've discussed before.  We have homework every night, and if you aren't sure about the assignment, what are you going to do about that in the next two minutes?.  You'll find out in class -- you know, the class that starts in two minutes -- what we're doing in class today.  I give these non-answers -- politely the first couple of times, with emphatic finality if they continue more than a couple of days in a row -- along with a reminder to get problems out and prepare for the quiz.  The dumb questions disappear pretty quickly, often when a student starts sarcastically giving my answers to his slow-witted peers.

Okay, that's how to handle the ridiculous questions.  But what about the important or reasonable questions?  You don't want to answer those right before class, either.  It's so, so easy to get caught up in a five minute discussion with the diligent student who will be missing two days of class next week, and wants to plan how to catch up.  That's a conversation that must be had -- but it doesn't have to happen now.  Don't make your class sit and wait for your conversation to finish, just like you don't want a store clerk to make you wait to check out while he and the manager discuss important issues about the end of tonight's shift.  Ask the student to come by after class, at lunch, or some other time.  Whatever reasonable questions there might be from individuals, they can all be dealt with later.  Get class started.

Two time-saving answers to common beginning-of-class questions I learned from colleagues at the AP reading:

(1) Hey, I missed yesterday's quiz because I was absent.  When can I make it up?  Don't bother... we'll just have tomorrow's count double.  Aha!  No more tracking down people for make-up quizzes.  And since I give a quiz every day, even really good or really bad performance isn't going to change anyone's grade significantly.  It saves me trouble, but also, what incentive to keep up!

(2) On problem two of this test, you took off two points, but I think you only should have taken off one point.  Let me show you what I meant.  Not now.  But if you'll place your test in this folder, I will be glad to carefully regrade the ENTIRE test tonight.  What is the probability that this student actually bothers to re-submit the test?  Chances are, the student is grasping at straws hoping to use debate skills to convince you of something.  And this student also knows in his heart that if you go through his test again with a fine toothed comb, you might find one or two other places where he didn't deserve awarded points.  You've arranged a perfect result, then -- if you truly made an egregious error, you'll be able to correct it, but you provide a disincentive to those who are merely whining.

Do you know a polite yet firm answer to a typical opening-of-class question that avoids protracted conversation?  If so, let us all know in the comments.

17 June 2015

Official Course Descriptions for all Woodberry's Physics Offerings

I'm often asked about Woodberry Forest's physics curriculum.  We require all students to take a full-year physics course during high school.  Those who enter as 9th graders take physics first.  Those who enter in 10th or 11th grade usually take physics in the junior year.  Below are all of our course descriptions, as published in Woodberry's course catalog.  

Nomenclature note: "3rd form" refers to 9th grade, "6th form" to 12th grade.  "Form" is archaic terminology referencing the benches in which students in olden-days Harry-Potter-Style boarding schools used to arrange themselves by class.  What we call the seventh grade sat in the first benches, and so was referred to as the 1st form.  

Feel free to email with questions and comments.  If you come to a summer institute or to the open lab, I can give you a CD-rom with tests, quizzes, and problem sets for each of the courses listed below.


Conceptual Physics
Conceptual Physics, the year-long, third-form science course, emphasizes the principles of physics on a conceptual basis.   The course begins with optics and waves and progresses through electric circuits before covering traditional mechanics topics. Students use the fundamental facts and equations of introductory physics as a vehicle for a thorough introduction to analytical thinking and creative problem-solving skills.

Approximately 50% of class time involves hands-on experimental work.  Nightly problems require students to justify their answers with substantial verbal reasoning.  Tests and exams questions are based on authentic items from New York Regents exams, adapted such that a calculator is not required, and adapted to require students to demonstrate their verbal as well as mathematical skills.  It is expected that a successful conceptual physics student leaves with a solid understanding of qualitative mathematical approaches to problem-solving, including verbal justifications of answers; graphical analysis, both experimental and theoretical; order of magnitude estimation, including describing the physical meaning of numerical answers; and experimental verification and investigation of physical relationships.

Physics is a year-long course appropriate for upper-form students with a background in algebra and lab sciences. The course approaches the same topics covered in the 3rd form Conceptual Physics course, with more emphasis on working qualitatively with physical concepts. The course begins with a study of mechanics, including kinematics, Newton’s laws, and the conservations of energy and momentum. Later topics include circuits, waves, and optics.

Students spend a significant amount of class time doing hands-on experimentation, developing an understanding of how to use experimentation to make or verify physical predictions. Other time is spent learning and discussing physics principles, and practicing their application in problem solving and justification. Homework consists of readings and problem sets, with an emphasis on logical, verbal reasoning. Tests and exams are based on New York Regents exam questions.

It is expected that a successful student in General Physics leaves with a solid understanding of qualitative and quantitative mathematical approaches to problem-solving, including logical justifications of answers; experimental and theoretical graphical analysis; order of magnitude estimation, including describing the physical meaning of numerical answers; and experimental verification and investigation of physical relationships.

Honors Physics 1
Honors Physics 1 follows the course description for AP Physics 1: Algebra-Based provided by the College Board. This is an algebra-based, college-level survey course, covering important topics in classical physics. Students are expected to develop both a mathematical and conceptual understanding of the subject, with a substantial emphasis on the latter.  The course is taught through the use of quantitative demonstrations and in-class laboratory exercises, paired with nightly assignments involving descriptive problem solving.  In weekly extended laboratory sessions, students design experiments to investigate the principles discussed throughout the course.

Tests and exams are in the style of the AP Physics 1 exam.  Students are encouraged to take the AP Physics 1 exam in May.  Honors Physics 1 is taught to three constituencies of students who may opt in: Any 12th grader who is interested, 11th graders who have completed a high school biology course or who are taking biology concurrently, and a set of 9th graders who are selected by the department during the first marking period.  The separate 9th grade section covers the identical material at the same college level.

Honors Physics 2
Honors Physics 2 follows the course description for AP Physics 2: Algebra-Based as provided by the College Board, along with a few additional topics. This is an algebra-based, college-level survey course, covering topics in fluid mechanics, thermodynamics, electromagnetism, atomic and nuclear physics.  Students are expected to develop both a mathematical and conceptual understanding of the subject. The course is taught through the use of quantitative demonstrations, paired with nightly assignments involving descriptive problem solving.  In weekly laboratory sessions, students design experiments to investigate the principles discussed throughout the course. Honors Physics 2 is primarily a senior course.  Honors Physics 1, or a placement test showing mastery of the skills and material covered in Honors Physics 1, is the required prerequisite.

Honors Research Physics and Physics C
From September until February, students research four problems in preparation for the US Invitational Young Physicist Tournament (USIYPT).  Faculty and students together investigate these open-ended, college-level projects.  A solid grasp of theory and intricate, involved experimental work is required.  The trimester exam is a 5-10-minute talk based on the research project.  As the tournament approaches, students are trained to conduct a “physics fight,” a ritualized debate over the merits of a solution.  Four members of the class are selected to be representatives of Woodberry Forest at the USIYPT.

Throughout the year students prepare for the AP Physics C – Mechanics or AP Physics C – Electricity & Magnetism exam, using the course description provided by the College Board.  Calculus-based mechanics or E&M is covered through nightly problem-solving as well as in-class review, demonstration, and discussion. Students are expected to develop both a mathematical and conceptual understanding of the subject so as to perform well on the May AP exam.  The physics faculty will in the spring select approximately eight students, including mostly rising seniors but also some rising juniors, to audition for Research Physics. The invitations are issued based on performance in previous science courses, and based on the skills and background knowledge each student could bring to the competitive physics team at the tournament.  The audition consists of a preliminary investigation into one of the USIYPT problems in the last weeks of May, followed by a presentation to the faculty during exam period.  Students must be invited to and pass the audition in order to take the course.

16 June 2015

Set up *ALL* AP Physics 1 problems in the laboratory.

"Laboratory" doesn't have to be a distinct part of a physics course -- it's just what we do, especially in AP Physics 1.

When I took high school and college science classes, "laboratory" was a special, separate portion of each class.  Most days the teacher would talk to us about facts and problem solving.  Once a week or so we would perform an experiment -- always going to a separate lab room in order to do so.  The laboratory portion of the course stood entirely separate, too, in terms of evaluation.  The idea of asking a test question in an experimental context was utterly foreign.  Sure, biology had "lab practical" tests in which we identified parts of a frog or worm*.  Those tests were still entirely in the experimental realm, just an alternative to a lab report.  A holistic integration of facts, problem solving, and experimentation was unheard of.

* Gross.  Now you know why I'm a physicist, not a biologist.

In the mid 1990s the AP Physics exams began including one question per exam based around an experiment.  Such questions required explanations of procedure as well as verbal and quantitative analysis of data.  I've often recommended to teachers that they could use these old test questions essentially as a laboratory course -- assign the AP questions on quizzes or tests, then use lab time to actually do the experiment.  

The AP Physics 1 exam also includes one free response question related explicitly to laboratory skills.  On the 2015 exam, that was question 2, about circuits.  It would be a simple matter to repurpose this question as a laboratory activity.  The first part asks for simple ammeter and voltmeter readings.  The second part asks students to determine whether a light bulb is ohmic -- my class did this exact experiment, graphing current vs. voltage, and found a clear curve.  

The hugely important point is, all five of the 2015 AP Physics 1 free response questions can be set up as laboratory activities.  

Question 1 asks for a qualitative prediction of how the acceleration of an Atwood's machine will change with added mass.  So set the situation up with two pulleys on a lab table, and use a motion detector to measure the acceleration with and without a cart included in the system.  

Question 3 puts a block on a horizontal spring, and asks for a graph of kinetic energy vs. time for the block as it leaves the spring and slides to a stop.  Use a compressible spring and a rough block on a track; a motion detector can record position and velocity data.  Vernier Labquests can be easily programmed to graph kinetic energy as a function of position, as on the test question.

Question 4 is the classic "does a fired bullet hit the ground at the same time as one that's dropped?"  Video analysis of this phenomenon is readily available.  A Mythbusters* episode was devoted to exactly this problem.  I use the ipad app "Coach's Eye" to record my PASCO projectile launcher shooting balls horizontally at different speeds.  The app shows conclusively that the balls hit the ground within a hundredth of a second of each other.

* Or perhaps it was a "Ghostbusters" episode.  Some students might have been confused on this account.

Question 5 is basically asking why each string on a cello or guitar plays a different note when plucked.  You could get some guitar strings and set them up over pulleys, exactly as in the problem. Then you could pose exactly the AP question as an open-ended, live-action laboratory activity.  No description necessary, though, just "Look here, why do these four strings play different notes?  Explain, and then do some sort of experimental test to see if your explanation is correct."

Last year in one of my summer institutes, we spent a morning setting up experiments to verify the answer to multiple choice questions on the released practice exam.  We found a way to do most of them.

The beauty of AP Physics 1 is that, with very few exceptions, all of the relevant topics lend themselves to classroom-scale experimental investigations.  They don't all have to be done as student-led, hands-on, multi-day laboratory activities, of course.  You can do quantitative and qualitative demonstrations from the front of the classroom.  You can have students make "quick and dirty" measurements sometimes rather than detailed graphs over a large parameter space.  You can collect and analyze data occasionally as a whole class rather than in individual lab groups.  

But you can and should do the experiments suggested by virtually every problem in AP Physics 1.  Fortunately, for me, the days of having one room for lecture and another for lab are long gone.  I don't teach a separate lab course, though we do perform a few extensive, multi-period projects along with quicker investigations.  My goal is to get student hands on equipment about three times per week, even if only for a few minutes on some of those days.

And what is my lab guide for all those 100 plus lab days?  Much of it is just the released AP Physics exams themselves.

07 June 2015

Please don’t give credit for baloney…

It’s Day 6 of the AP Physics reading.  I’ve been grading physics 1 problem 4 (the paragraph about projectiles) and physics 1 problem 2 (the experimental circuit question).  Both questions require me to read through a lot of student writing. 

I don’t mind reading paragraphs.  How students communicate in words and sentences says a lot about their physics knowledge.  I am more comfortable than ever this year that we are awarding points for good physics understanding rather than simply for performing mathematical tasks. 

As the reading drags on, though, I’m becoming increasingly frustrated with walls of text full of sound and fury, yet signifying nothing.  Why would you repeat the question’s prompt at me four times?  Do you think I’ll give up and award credit the fourth time?  Why do you think it’s important to tell me how carefully you set up your experiment?  Why must you go on and on about the negligibility of air resistance, or how this experiment isn’t really going to work, actually?  Please, please, students, just get to the point. 

But teachers, these long-arse essays devoid of meaning are our fault, too.  Somewhere in their physics classes, too many students have been earning credit for verbal diarrhea.  It’s our job to stop the madness.

Next time you grade a text, just stop reading when it’s apparent that the student has no clue what he’s talking about, but is hoping to throw enough words at you to earn a few points.  Then when the student comes to you to indicate the one word that might possibly have earned a point based on the rubric, be firm.  It’s the student’s job to be clear, not your job to give him the benefit of the doubt.  It’s the student’s burden to show you that he knows the physics, not your burden to make assumptions.  If you can’t interpret a response clearly on first reading, the student has not been clear enough – and so should lose credit.  No pity, no remorse, no exceptions.

Furthermore, what is the student doing asking you to re-interpret his test, anyway?  Unless you failed to read a page or something obvious like that, just refuse.  I have been grading AP exams for 16 years, and I have yet to see a student coming to me along with his test to clarify what he really meant.  So if I might have misinterpreted a student’s test response at the cost of one or two points, tough.  He’ll probably be clearer next time.

Please, for the sanity of all the 310 AP physics readers, teach your students to write concisely.  I will be happy to help you out if you need backup in defending your grading to your students – please email me.  Perhaps I ought to inflict a week of essay grading upon those teachers who still give credit for baloney…