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15 May 2022

Live Physics Time: the 2022 AP Physics 1 exam

Folks, I'll be live Monday morning May 16 on starting at 6:15 am to discuss the 2022 AP Physics 1 exam.  During the show, I'll be checking my alternate email, gregcjacobs at gmail.  Send something if you have a question you'd like answered!

The show will be archived on the showreel.  Listen live if you'd like to join the conversation via chat or email; or listen to the archive if you can't get up that early.  :-)

As always, the show is live during the morning dog walk.  Don't expect polished infotainment - expect a friendly, informal conversation about physics and physics teaching.

(And if there's further demand for discussion, I'm happy to do another LPT later in the week.)

24 April 2022

AP Physics C in April - don't worry about math!

I'm working on the final set of test corrections with my Physics C - mechanics independent study student.  This person did well on the test - earned a 4 on a typical AP scale.  But that's only 50-65% of the available points, so there are plenty of items to correct.  

This student had AP Physics 1 with me two years ago.  He is in AP Calculus BC.  

In the first part of the year, I had him focus on the mathematics that overlay the concepts he learned in Physics 1.  He watched all the "AP Daily" videos for Physics C, he practiced new mathematical techniques like integration to find displacement/work/center-of-mass-location/rotational inertia.  He's got those techniques down, now - at least, he'll do the math right most of the time if he sets up the problem right.

And there's what we're concentrating on now - setting up the problem right.

AP Physics C students usually want to do math.  They plug into equations, manipulate, see if the answer is right... and if not, they try a new approach, until (a) they get what they think is the right answer, or (b) steam comes out of multiple orifices.  Neither result is useful.

I don't want to see much math right now, for these corrections.  I want to see facts and concepts.  How should this problem be approached?  How do you know the problem should be approached that way?

For example: I don't want to see plugging and chugging into energy or momentum equations until I see a clear statement of what is conserved and why.  How do we know?:

Mechanical energy is conserved when there is no net work done by external forces.  (And when there’s no internal energy conversion.)

Angular momentum is conserved when no net external torque acts. 

Momentum in a direction is conserved when no net external force acts in that direction.

I need to see these facts, along with a statement as to why they apply.  Then I need to see that they used the right formulas for each term - including direction of momentum - and/or that they made a correct energy bar chart.  That's it.  The actual mathematics to finish the problem isn't relevant right now.

As this student has brought me corrections, I've deliberately checked off a few which were set up correctly, but led to the wrong answer due to a math error.  And, I've send him back to try again for a few corrections in which he got the right answer, but didn't communicate the starting point clearly.

All this works, except when he notices that his answer is wrong, but I tell him the setup is correct.  "I've got to get it right!  It's going to bug me forever if I don't!"  I totally get it!  But, trying to find a math mistake is not a productive use of time.  Usually the issue here is something like a squared term not being copied correctly from step to step in the mathematics; or, accidentally canceling a 1/2 in most but not all terms. 

These little math mistakes are difficult to find in a half-page worth of work; but, given a new problem from scratch, this student - or any competent AP Physics C student - would NOT generally make such a mistake!  Rather than spend 20 minutes doing and redoing a problem until the math works out, why not move on to the next one?  

Most of the errors that students make come from starting with the wrong approach.  Most of the time, the right approach leads to the right answer.  So in our limited review time, we're going to focus on the right approach.  We'll let the chips fall where they may on whether the math gets done right.

23 April 2022

Mail time: AP laboratory questions using "equipment usually found in a school physics laboratory"

A post to a physics teaching message board asked the (paraphrased) question:

I was wondering about "design a procedure" AP Physics questions that ask students to use "equipment usually found in a school physics laboratory".  What are the limits here?  Would readers take off if a student used, for example, an accelerometer?

An accelerometer is fine.  It's available in the Pasco/Vernier catalogs and on smartphones - that's way common enough for me!

In general, I wouldn't stress about what's "common" or not.  No one is lawyering up about "well, this is only used in 49.1% of high school physics classrooms, so minus two points from Gryffindor."

Much more importantly, make sure your students can (very briefly!) in their procedural description show that they know how the device is used.  "Plot acceleration as a function of time using an accelerometer mounted to the cart" makes sense.  "Carry a phone on the roller coaster, and look at the acceleration-time plot using the built-in accelerometer."  Those are fine.

"Point the accelerometer at the cart to get its acceleration" doesn't work.  :-)  An accelerometer isn't a radar gun, nor is it a magic wand*.  I often see this issue with e.g. a photogate - it's not a point-and-click device! 

*Using it as such *would*, in fact, result in minus two points from Gryffindor.

Similarly incorrect would be, "Launch the ball from the projectile launcher.  Use an accelerometer to get its acceleration during the launch."  Now, I suppose you might be able to crack open the ball, insert a miniature accelerometer, paste the ball back together, launch the ball... but no.  That's not at all "common".*

* If someone truly did go through all this description, though, the procedure works.  Way ridiculous and time-wastey, but would such a student show comprehension of experimental physics?  I'd say so.  Point is, just saying "use the accelerometer" in this case isn't good enough for the readers to infer this farfetched procedure.  But if they write out all this detail, then sure, they have demonstrated serious understanding.

A diagram can do the work of the words here, too.  If a student shows the accelerometer attached to a cart, or a phone mounted to a cart or something, then it's clear the student understands what an accelerometer is and how it works.

Hope this helps!


14 April 2022

A birthday at Chuck E Cheese - and "good intentions"

As part of my boarding school responsibilities, I serve as "advisor" to a group of students.  Yes, I help them choose classes, but my role as advisor goes well beyond pure academic advising.  I'm the first point of contact for their parents with the school, and for these eight students when they have questions about anything at all in the complex ecosystem in which we live.  We eat together once a week as a group, giving us a chance to share stories, to get to know one another.  

And, in my group, I arrange a birthday celebration for each student.  Usually these past couple of pandemic years, that's meant simply me getting take-out from a restaurant of the birthday boy's choice, plus cake and a chorus of "happy birthday."  Sorta predictable, but a meaningful diversion in a busy, demanding schedule.

Well, we're clear to take the students out to restaurants again.  Yay!  When it was Alexander's turn to choose the birthday event, he did ask to go out.  To Chuck E. Cheese.  

Sounds like fun, I said.  I remember going to several birthday parties at Chuck E. Cheese when I was younger.  It was a rather commonplace event - my wife says she used to go to "Showtime Pizza", which seems like the same sort of thing.  But Alexander - and five of the seven students who ended up on the trip - did not grow up in America.  A Chuck E. Cheese party was an exploration of American culture, similar to attending a baseball game, a Broadway musical, or a rural county fair.

I made the party reservation, on which I had to indicate the age of the birthday boy or girl.  The form did in fact allow me to input Alexander's new age: 19.

Most of these boys didn't know what to expect.  All got on the bus for the hour-long drive on a Sunday morning with a mix of excitement and skepticism.  Would this be fun, or stupid?  Or both?  Time is the currency of our school.  They were committing something like four hours of their precious free time to this event.  Will this be worth it?!?

Our wonderful host Reyna greeted me and the group, and quickly upsold us on more food.  (I knew ahead of time that two small slices of a medium pie each would not cut the mustard for these 16-19 year old boys.  Make 'em extra larges, let Alexander choose the toppings, and make it four or five slices each.  Plentiful food is a boarding school social lubricant, as would be alcohol for an adult gathering.)  She gave everyone wristbands for the games, and sent the students on their way to play.

After plentiful skee-ball, pop-a-shot, and other arcade games, the pizza arrived.  Two students seemed to have disappeared, but they emerged from the Mario Kart cave eventually.  (If they had been 7, I would have worried at their absence!  I figured these rather bigger boys would show up for food.)

My wife Shari and I were a bit disappointed that the restaurant no longer features an animatronic rat band.  That was the big feature of 1980s Chuck E. Cheese birthdays - the serenade by the creepy clicking plastic figures.  Instead we got just a video screen welcome.  But...

Apparently someone told the salad bar operator to go put on the rat costume, because OUT CAME CHUCK E. CHEESE HIMSELF!!!  The video board played a birthday song, and Reyna encouraged all of us to do a birthday dance with Chuck.  In the event, only one of my group - Taeho, the man from Gangnam, Seoul - danced.  Alongside every 7 year old in the restaurant and the poor soul in the rat costume.  The rest of my advisees looked on... but they were smiling.  They were, indeed, entertained.  I have pictures.  Not that I'm going to show you, because I want my advisees to be employable in the future.  But I have pictures.  Everyone, Alexander included, enjoyed the party.  It was worth the time and effort.

Why am I writing about Chuck E. Cheese on a physics teaching blog?!?  Because of the conversation I had with Reyna while the 16-19 year old "boys" cashed in their arcade tickets.

"Thank you for working with us," I told her.  "I expect you're not used to teenagers."  I didn't expect her response - Reyna was effusive about the experience.

"I was nervous at first," she said.  "I saw that Alexander was 19.  We do get people who come with bad intentions - 23 year olds who just want to make fun, or insult, or be stupid.  But I could tell when I first talked to your group that they were excited.

"You, and they, came with good intentions.  I can tell they had a great time.  And I was glad to be a part of that."

That's the lesson.  Teenagers are in fact a despised underclass outside the confines of a school - and, if you listen to too many teachers kvetching in the faculty lounge, often even within schools.  Reyna pushed through her prejudice, even though her prejudice was born of authentic experience.  She kept an open mind, and treated my teenaged, ethnically-diverse advisees with respect, with the assumption of good faith.  And we were all the better for it.  (Especially the restaurant's bottom line.  Rat pizza ain't cheap.)

Thanks, Reyna.  

30 March 2022

AP multiple choice question: angular momentum change for a rebounding sphere

One of my favorite questions from the 2014 released AP Physics 1 practice exam involves angular momentum in a collision between a sphere and a pivoted rod.  Teachers can check out the question (I think) at this AP classroom link.  (If that doesn't work, search the AP classroom question bank for "A thin rod of length d".)

In this question, a sphere bounces off of a pivoted rod.  The rod rotates after collision, and the sphere rebounds with a given *linear* momentum.  The question asks for the change in the rod's angular momentum as a result of the collision.

Some folks have tried to understand the solution by combining linear and angular momentum.  But that's not correct!  It's never allowed to combine linear and angular momentum in the same equation - you've gotta either conserve one or the other.  Linear momentum never transfers to angular momentum (nor vice versa).

This particular AP question explicitly asks about angular momentum.  Therefore, even though the problem gives the linear momentum of the sphere as pf and pi before and after collision, we've got to use conservation of just angular momentum about the pivot.

Angular momentum of an extended object is Iw.  That's what we'd use for the rod, if we needed it.  For a point object, angular momentum is mvr, where r is the distance of closest approach.  In this problem, the variable is the closest the ball ever can get to the pivot, so is the distance of closest approach.

Now, the change in angular momentum of the rod is equal to the change in angular momentum of the ball - that's what angular momentum conservation means!  The ball's change in angular momentum is (mvid) - (-mvfd), because the ball rebounds - it changes direction, represented by the negative sign mathematically.  The negative signs cancel to make a positive sign.  Here the masses m and speeds vi and vf aren't given, but the linear momentum is: mvi *is* pi, and mvf *is* pf.  That's where we get pfd + pid as the answer!

29 March 2022

2022 Conceptual Physics Summer Institute: July 16-17, Registration open!

Announcing the 2022 CPSI!  This year, I'm only offering a single session, the weekend of July 16-17.  We'll take up to 40 people, but when we're full, we're full! :-)

Folks, I'm already teaching several AP summer institutes - see the left-hand sidebar for details.  But what if you are looking for physics professional development that is NOT aimed at college-level physics?  I mean, I meet so many of you each year who teach on-level, honors, college-prep, Regents... to all ages, to all varieties of student.  And in my personal mission to spread physics knowledge to as wide an audience as possible, these sub-college courses represent a critical first point of contact with our discipline.  I focus as much energy on my conceptual course as on my AP course each year.  So I'd like to focus some of my summer professional development expertise on those who teach these first-level courses.

We've done this for two years now.  See the comments at the end of this flyer for participant reviews.  They all say, this institute was an amazing, friendly, and productive experience.

I'm offering a two-day institute on July 16-17, 2022.  It will be online, broadcasting via Zoom from my lab.  Skip past the institute description for fees and registration instructions.  The single session will be limited to the first 40 who sign up.  The daily agenda is included here at the bottom of the page.

Jacobs Physics
Conceptual Physics Institute Description
July 16-17, 2022

All levels of high school physics can be taught conceptually – where verbal and experimental reasoning is prioritized over mathematical problem solving.  While mathematics are used extensively, they are used as a tool to create predictions about the workings of the natural world.  Whether you teach “general”, “on-level”, “honors”, “Regents”, or “college-prep” physics, a conceptual approach can be adapted to most any introductory physics topic – and to most any state or district standards. 

In our institute, we will discuss, practice, and share methods of teaching common physics content in a conceptual style.  I will be broadcasting from my laboratory via zoom.  Time will be devoted to experimental methods that are especially useful at the sub-college level; to course planning on a year-long and a unit basis; and to best-practices physics pedagogy, which differs substantially from pedagogy in other disciplines.

Participants will be given a full-year’s set of classroom-ready materials, including fact sheets, in-class and laboratory activities, assessments, and planning documents.  More importantly, through their interactions with the instructor and with their colleagues, participants will develop skills and ideas for adapting these materials to their specific classroom environment.  Those attending will also earn a certificate indicating their participation in 15 hours of physics professional development.

How much does it cost:  $200 for the weekend.  The schedule of events is listed below.

How do I register?
(1) Click the "donate" button below (or in the left column of the blog).  It will take you to paypal.
(2) Enter $200.00 as the donation amount, either through paypal or credit card
(3) Click "Add special instructions to seller" or "Add a note"
(4) In the note, please include your name, preferred contact email, and institution
(5) Fill in payment info and click "donate now"
That's all - I'll be back to you within a day or two confirming your registration, and sending you links to the classroom-ready materials.

Cancelation issues: If you register then can't attend, contact me via email.  As long as I can replace your spot, I'll send a full refund; if I can't replace your spot, I'll refund all but $25.

Schedule: Each session will include both whole-group presentation/discussion, and breakout groups for activities.  In between sessions and during breaks, Greg will be available for informal conversation. 

Saturday 16 July (all times eastern time)
10:00               Introductions
                        What does “conceptual” mean – defining levels of physics
Different levels of physics: developing your program
                        Different levels of physics: developing your resources

11:30               Eight styles of physics laboratory activities
            Including the two best-adapted for conceptual physics
My first day activity – reflection experiment
My first group laboratory experiment – refraction

1:00-1:30    break

1:30                 Sequencing your course
Starting the year right: the most important physics teaching skill
Justifying answers with facts
Simple ray diagrams for optics in conceptual physics
Justifying answers with equations
In-class laboratory exercises: circuits

3:00                 The daily “quiz”
Tests and quizzes, targeted to different levels
                        Other sorts of assessment
                        Preparing for the trimester/semester exam
                        Adapting a conceptual course to external standards
                        In-class laboratory exercises: motion graphs

Afternoon – asynchronous
                        Read through the shared files
                        Read through the Jacobs Physics blog
                        Adapt to your district or state standards
                        Bring questions and ideas for the social or for Sunday

7:30                 Optional Zoom social: Dinner, dessert, drinks, and conversation.  BYOB, obviously. 

Sunday 17 July
10:00               Building and creating experiments with whatever you’ve got
                        Developing your own in-class lab exercises
                        Using or substituting inexpensive equipment
                        In-class laboratory exercises: direction of force and motion

11:30               Methods to speed your grading
                        In-class laboratory exercises: forces in 2-d
                        In-class laboratory exercises: motion in 2-d
1:00-1:30    break

1:30                 The final third of the year – once skills are built
                        How I teach impulse/momentum
                        Energy bar charts at the conceptual level      
                        Laboratory exercises with harmonic motion

3:00                 Sharing: Any Other Demos
Online simulations:
                                    The Physics Classroom
The Physics Aviary
                                    Vernier’s Pivot Interactives
                        Ending the year: the Physics Fight

24 March 2022

Extended facts about orbits

In November when I *first* introduce Newton's Law of Gravitation and orbits, I keep things very simple.  I give the equation for gravitational force, define a gravitational field, and that's about it.  

We do a practice exercise where students must use circular motion facts to determine how the speed of a satellite in orbit depends on various parameters.  (We test predictions using an online simulation.)  You can see me do this exercise in AP classroom, on 3.8 Daily Video 1.

There's more to understanding orbits.  But students weren't ready for that "more" back in November.  Now they are.

In March as we begin our "tapering" review toward the May 12 exam, I want to revisit topics we've discussed previously, but in greater depth.  With regard to orbits, back in November we didn't know about energy or angular momentum!  Now we do.  So let's go back and discuss orbits again, this time with EVERYTHING we can think of.

Below are the NEW facts I'm bringing up, facts I ignored earlier in the course, alongside some commentary.

Two Types of mass:

Gravitational mass is measured using any relationship that involves a gravitational field or force.

Inertial mass is measured using any relationship that does NOT involve g, such as netF = ma or 


In all experiments ever performed, gravitational mass is equal to inertial mass.

Early on, I'm excited for students to simply understand that 100 kg is not a force, and that a 100 kg object on the moon has a mass of 100 kg.  There's no way I'm gonna try to explain the very subtle difference between gravitational and inertial mass!  Now, though, it's okay to add this subtlety on.

Gravitational potential energy

Near the surface of a planet, the potential energy of a planet-object system is mgh, with h = 0 at the lowest point of the motion.

Away from the surface, the potential energy of a planet-object system is treated differently:

·         PE is larger the farther from the planet’s center.

·         PE has a negative value (except when the object is way far away from the planet, in which case PE is zero).

·         The equation for potential energy is

Don’t use this equation unless you must derive an expression.  The negative sign is confusing.

That last italic piece is important.  Most AP1 orbits questions are not going to use this actual equation!  The first bullet is the big deal... planets getting farther away from one another increase their potential energy.  That means the potential energy gets closer to zero, gets less negative... but that subtlety is beyond many of my students.  Not to worry!  These facts will allow for a correct and clear answer to virtually any gravitational PE problem.

In a circular orbit of a satellite around a planet, consider the planet-satellite system:

·         Kinetic energy is constant (same speed)

·         Gravitational potential energy is constant (same orbital radius)

·         Angular momentum mvr is constant (no external torques)

·         Total mechanical energy is constant (no external work, and no internal energy)


To find the speed of a circular orbit, set gravitational force

 equal to ma, with

In an elliptical orbit of a satellite around a planet, consider the planet-satellite system:

      ·         Kinetic energy is NOT constant (speed changes)

      ·         Gravitational potential energy is NOT constant (orbital radius changes)

      ·         Angular momentum mvr is constant (no external torques)

   ·         Total mechanical energy is constant (no external work, and no internal energy) 

Now that the class is well familiar with the concepts of energy and angular momentum, I want to be explicit about conservation in orbits.  This set of facts is also a good reminder/reinforcement of the statements elsewhere in my fact sheets about the conditions under which mechanical energy and angular momentum are conserved!

18 March 2022

Woodberry Forest Conceptual Physics Tournament - May 22 2022. Come be a juror! (We will pay...)

In my school's conceptual physics program, we give cumulative written exams after the first and second trimesters.  In lieu of a final exam*, we are once again running the Woodberry Forest Conceptual Physics Tournament!  This is a competition for 9th graders, to be held at 1:00 on Sunday May 22 2022.  We've done this before, in 2017 through 2019.  Now we are back.

*No, to be clear to all, we're not giving an A to the winner and an F to the person in last place.  That's silly.  We're just having a fun, competitive tournament, to determine a winner.  Jurors engage in discussion and conversation with participants about their problems.  Jurors then award scores and write comments for the participants; jurors aren't assigning grades!

How does this tournament work?

On May 2, I will reveal a slate of three problems to the 68 participants.  These problems will be in the style of AP Physics 1 "paragraph response" questions.  Except, rather than just answer in a paragraph, the students will spend the month of May setting up experiments to provide evidence for their answers.  By tournament time, each student will be expected to be prepared to discuss the solution to two of the three problems, with both theoretical and experimental support.

At the tournament, each student will participate in two "physics fights."  Think of these physics fights like a miniature version of a graduate thesis defense.  Students will have a strict limit of two minutes to present their solution to a group of two or three jurors, who then will engage each student in conversation about the problem for five minutes.  The students are evaluated by the jurors not only on the quality of their solution, but also on their ability to discuss the solution, to confidently hold a conversation with the jury.

Importantly, jurors are explicitly instructed on their primary role - to find out how much the students DO know, not to expose what they don't know.  

How do the students prepare?

Starting on May 2, all conceptual physics classes the rest of the year will be devoted to tournament preparation.  They'll set up experiments in class, they'll be assigned to write up their solution as homework, they'll practice presenting.  

Most importantly, our AP physics classes will spend their final weeks of the school year serving as mentors to the conceptual students.  I will assign each AP student to lead groups of two or three 9th graders.  The AP students will dive into the problems with the conceptual class, helping to create and analyze experiments, helping the freshmen to understand the details of their presentations, and serving as mock-jurors in practice sessions.  This mentoring serves as the final project in lieu of the exam in the AP classes.

We need jurors.

The key, I think, to any class project is external assessment.  I and the other conceptual physics teachers will play the role of coach and advocate, always encouraging and helping the students to deepen their understanding of the problems and to improve their presentations.  Our relationship will be purely supportive, enthusiastic, positive.  

We can't then turn around and grill these same students as examiners!  That'd be like our football team's coaching staff refereeing the state finals.  Even -- especially -- if their officiating were fair, the coach-student relationship, both in before and after the game, would be irrevocably compromised.

So we need jurors.  We can pay.

Would you like to come to Woodberry on May 22 to be a juror?  We'd ask you to arrive at lunch time, like 11:30.  We would have a meeting of all jurors in our beautiful dining hall over lunch.  

Then we'd ask you to be a juror for a couple of hours' worth of physics fights.  You'll be partnered with several other examiners over the course of the afternoon, getting to know a diverse set of fun folks from all over.  When all students have presented their two physics fights (to two separate juries), we'll gather the jurors for conversation, coffee, snacks, and their paycheck.

In any case, our goal is to be done by 3:30, or possibly 4:00 if there are logistical issues.  No later -- our students will be attending the final seated meal with their advisors that night followed by study hall, so we can't run late.

We will pay you $100 plus lunch (and even dinner, if you'd like to stick around) for your time.  (If you're coming from more than a few hours away, we can put you up on campus on Saturday or Sunday night.) I think you'd find that the camaraderie among the jurors and the engagement with the students will make the trip worthwhile.

Who's eligible as an juror?

Anyone who has passed a college-level physics class.  This includes alumni of your advanced physics class, even if they're still juniors or seniors in high school - we've had several teachers bring a van of students, and they've had an awesome time.  We've had local college or graduate students on juries, we've had parents, alumni, colleagues who teach other subjects, grandparents, friends... Anyone willing to engage in conversation about physics at the high school level, as long as you can recognize good and bad physics, we'd love to have you.  We are looking for a diverse juror pool, which especially includes diversity in age - truly, we want folks in their teens as well as folks in their 70s, and everywhere in between. When I run the USIYPT, I find the mixture of undergraduate / graduate / professor / high school teacher / industrial physicist / retired physicist on the juror panel allows some amazing relationships to develop.  I'd love to create a similar vibe here.

How can I sign up?

Send me an email, or contact me via Twitter, or call me -- my contact information is on the Woodberry Forest School faculty page.  I'll send you more information, including the three problems, and our current draft of the scoring rubric.

We would like to get 54 jurors - the first 54 who sign up.  I can't wait to see some blog readers - I'll even introduce you and your students to my pet hippopotamus, Edna.  :-)

08 March 2022

Fluids is Coming - what equipment do I need?

Reader Ryan writes in:

I saw the potential changes to the CED in AP Physics 1 with Fluids being added as a unit. What supplies would you recommend for this unit?

Good news is, you've got a couple of years.  The only substantive change in the works for P1 is to add a fluids unit to the other seven existing units.  And, this change will take effect for the 2024 exam.  

Fluids is nice because, well, the primary thing you need is a fluid - and water is plentiful.  :-)  I'm gonna have to think and decide what is worth money and what's not.  I mean, Bernoulli can be demonstrated with a hose, or with a tennis ball can.  You probably already have identifiable metal cylinders in your chemistry department that you can use to discuss Archimedes principle. Problem 2 on the 2010 AP Physics B exam is one I wrote based on an experiment I do - but with water, not oil.  I mean, it's easy enough to do this experiment with alcohol or vegetable oil, but it's much messier to clean up.

I'm sure I'll post other ideas eventually, but nothing strikes me as a must-have like smartcarts or photogates or carts-with-tracks.  I'd hold off buying stuff, and then when you see something that would make your life easier, buy it then!  If you have a limited budget, don't spend anything at all on fluids, just add more smartcarts or similar.

19 February 2022

Most of the class just got zero on a quiz. What now?

I gave my AP Physics 1 class an AP-level problem as a five-minute start of class quiz.  It described a block-spring system on a table, and asked students to graph various forms of energy "as a function of position" on the labeled graph provided.

Thing is, I've emphasized energy bar charts so much, about half the class didn't pay attention to the question prompt, or the labels on the graph.  They just reflexively used the grid to make an energy bar chart.  That earned zero points on the rubric.

And then half of the remaining students got no points for their graphs, which seemed to be made by three hundred monkeys sketching for three hundred seconds.  

What now?


I explained how to solve the problem correctly, and each student graded someone else's to the rubric.  Some folks asked good questions; some copied down the correct answer and reasoning.  Some just graded the problem in front of them.  I collected the quiz, and we moved on.

How did we avoid complaining about the fairness of this question, or of life in general?  Through significant culture building since September.  This class long ago accepted me as an ally and coach, someone whose mission is to train them to prepare on the May AP exam.  They know in their collective souls that I wasn't making some sort of chest-thumping point about how dumb they are (or how smart I am).  They know that when they don't understand something, they've discovered an opportunity to learn and improve, not an excuse to be (figuratively) spanked.

Of course, no one feels good about missing every possible point on a quiz!  I don't want fluffy-bunny "I'm so happy for my zero!" responses - sarcastic or not - from my students any more than I want them paralyzed by shame.  

I don't mind that my students' egos were bruised a bit.  A quiz can hurt.  That's okay.  It's like a softball team losing a game - if you don't care that you lost, you're not invested enough in your team's success.  But if you're gonna throw a tantrum and quit, well, you've got a lot to learn about losing graciously.

The ideal response to a loss is to find something to improve upon for next game, acknowledge the hurt... and move on with lesson learned.  Same thing here.  I want my students to find one thing they could have done better and move on.  Even if that one thing is as simple as "when a problem asks me to sketch a graph, I need to draw a function, not make a bar chart or a free body diagram."

Because I saw how many students had drawn an energy bar chart, as we graded I pointed out the language of the problem, and explained how "sketch a graph" must be interpreted.  I solved the problem and described the rubric.  When we finished, (as always) I asked the student with the high score to choose the music to be played during the remaining lab time - it was important for all to hear that several folks got 8s and 10s out of 12.  They couldn't rationalize that "no one" understood the quiz - clearly a few people did!

Okay, but how did we build culture to eliminate whining?  It was a long process, and started the very first week.  I think it's important to call out complaining, whining, or sour-grapes rationalizations the very first time we hear them; and to follow through, again and again.

"Oh, we have a quiz today?  Ugh, I'm gonna fail."  We have a quiz every day.  Would you dare tell Coach Dugan* that you're planning to strike out four times today?  What would he say if you did?

*Played by Tom Hanks

"This grading is ridiculous, how were we supposed to know to use the variable g rather than 10?"  Excuse me?  I'm not comfortable with the tone of your question.  Now, if someone else has a similar question, they may try to ask in a respectful manner, and I'll gladly answer with reference to official AP scoring principles.

"I lost a lot of points just because I didn't understand what "magnitude of the acceleration" meant.  I could totally have done this problem right!  What can I do about that?"  You can do better next time you encounter the word "magnitude" on a physics problem.

"This totally isn't fair - most of the class failed the quiz.  Are you going to give us extra credit?  When everyone fails, it's not our fault."  If you have an issue with the content or difficulty level of the test, contact information for the College Board is available on their website.  You may explain your concerns to them.  Until they make the changes you request, though, I'm preparing you for the exam the best way I know how, and I will continue to do so with content commensurate with the difficulty of the real exam.

You know you've won this particular battle when the students themselves are giving these sorts of replies to their classmates.  See, the majority of your class want to focus on physics, not grub for points.  The majority want the loudmouth arguers to be quiet.  The majority will appreciate you setting a positive tone.  And then the culture reinforces itself in the long term, such that terrible performance on one quiz becomes a mere blip.