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31 March 2020

Mail time: What equipment did I use for rotational motion demos?

Edna fan art by @aldescery
On the March 25, 27, and 30 AP Physics 1 youtube review shows, I used some equipment to make angular velocity-vs. time graphs, and to spin my pet hippopotomus Edna around on a rotating  platform.

Julia was one of many physics teachers who asked, where did I obtain the rotating disk (from show #1) and the rotating platform (from show #4)?

Julia and everyone, I'm so glad you're watching!

The Pasco rotary motion sensor can make angular position, velocity, and acceleration vs. time graphs.  I have the new wireless version, which works via bluetooth with my phone or ipad on the free "Sparkvue" app.  That's what I used when I had the two objects connected by a string over a disk.

The rotational platform is a big investment.  When we built our new science building in 2012, I had a nearly blank check to buy equipment - so I bought the Pasco complete rotational system.  Just the base and the disk attachment would be enough.  It's structured so that a Pasco-branded photogate can mount beneath the disk and measure angular velocity rather, um, more elegantly than I did on Monday's show.  But I only have Vernier-brand photgates, which don't fit.

When I did my open lab for teachers a few years back, we spent a few hours taking a trip to the hardware store to create the $5 version of this rotation system.  Get some 1/2 inch PVC pipe and two 90-degree attacher joints.*  Make a "T" out of the PVC.  Place the bottom part of the T over top of a securely-mounted ringstand... the top of the T will rotate pretty cleanly.  You can wind a string around the PVC to provide a torque, just like I did on Monday's show!

*Can you tell from the language use here that I have no skills with hardware? 

29 March 2020

Official AP Physics 1 Review Show - Monday Mar 30, noon EDT, N2L for rotation

Edna, my pet hippopotamus, takes a ride as we prepare for Monday's show:

Josh Beck and I are creating AP Physics 1 review shows every weekday at noon eastern time.  These are available live or on demand at the Advanced Placement youtube channel.

While the schedule will be announced a few days in advance of each show, here's what we've done so far:

Mar. 25: Greg, rotational kinematics
Mar. 26: Josh, torque in equilibrium
Mar. 27: Greg, experimental design based on torque in equilibrium

And here's what's on tap next week:

Mar. 30: Greg, Newton's second law for rotation
Mar. 31: Josh, connecting linear and angular speed
Apr. 1: Josh, rotational kinetic energy
Apr. 2: Greg, angular momentum
Apr. 3: Greg, equilibrium of forces

The advantage of watching live is that you can join the community via @JacobsPhysics on twitter; you can even submit questions for me to answer during the show.

26 March 2020

March 2020 AP exam updates - *we don't know* about format.

Hi everybody!  Hope you've been tuning in to me and Josh Beck on the Advanced Placement Youtube Channel.  We'll have a show for you every weekday at noon eastern, at least until exam time.

I'm posting here because I keep hearing incorrect and speculative statements about the 2020 AP exams.  Be just as careful about AP misinformation as you are about COVID misinformation.  Okay, maybe not quite as careful...

What is known:

1. The AP exams will in fact exist for 2020.
2. They will be taken from home, electronically.
3. They will be 45 minutes long.
4. They will not include straight-up multiple choice questions.
5. If you or someone you know needs help with connectivity for the exam, go to

That's it.  Everything else you might have heard is false or unconfirmed as of March.  Further announcements will come on April 3.

What is the format of the questions?  How will answers be input?  No one knows.

The development committees are working quite actively to figure out the answers to these questions.  I don't know how, or how well, any of this will work.  The College Board and ETS are trying very hard to adapt to a New World Order.  Compromises will be made.  It won't be perfect.  But I do trust the people on the development committees to do the absolute best that they can to create a good exam.

Please don't speculate.  Please don't spread rumors; if a student starts a sentence with "I heard that..." please gently end the conversation.  And I'd end it with the following:

The AP Physics test, in any format, tests a student's ability to communicate an understanding of physics principles.  If you know your physics, you'll do fine... no matter the format.

The AP exam cannot ever be "gamed".  If you're trying to find the One Weird Trick that will get credit on a certain style of problem, then, well, you're doomed.

Just practice the same kinds of questions we've always practiced in our courses.  That's all you can do, anyway.


22 March 2020

2020 AP updates, and I'll be doing AP Physics 1 review classes for the College Board...

Folks, as the Horsemen ride, massive changes are happening in the world of AP Physics.  Take a look here for official announcements.  (I really hope that this link goes inactive someday in the future... someday when we can again congregate in public.)

The quick summary for AP Physics 1 in 2020 only:

* Testing will be available online from home.
* Electricity, circuits, and waves will NOT be on the exam.
* The AP reading will done online.

A lotta more details are available on the announcement page.  And I've no doubt even more details will show up in the next few weeks.

Online review, hosted by Greg!

The College Board has tapped a bunch of folks to do a set of online review classes in every discipline.  For AP Physics 1, your hosts are: North Carolina's Josh Beck, and me.

Starting Wednesday March 25, and continuing through at least the end of April, Josh or I will be on live at noon eastern time via the Advanced Placement Youtube Channel.  The sessions will be available asynchronously* as well as live. 

*There's a word that I may have seen like thrice in my life before last week, and now it's part of my daily vocabulary 

We're still working out the topics for each session.  These will be posted on the channel. 

I'll be broadcasting alone from my classroom - I live on campus at my boarding school, where the classrooms are sanitized, private to each teacher, and for now open for business.  That means that I have access to my equipment.  For example, the March 25 class will be about rotational kinematics.  I've got quantitative demonstrations set up with a PASCO wireless rotational motion probe.  Friday I'll be doing a class about experimental design, focusing on torque in equilibrium - again, with live demonstrations.

If you have thoughts or suggestions or comments, please contact me via twitter - I'm @gregcjacobs, though for students during the live sessions I'm going to try using @JacobsPhysics.  We'll see how that all goes. 

Remember, we're all new to this world of exclusively online interaction.  Expect my classes to be raw - fun, engaging, but not a polished television show.  I'll screw up on air.  That's okay.  It's authentic.

19 March 2020

Jacobs Physics Podcast: Season 3, episode 2: AP Physics 1 2019 problem 2, the modified atwood machine

Today we discuss the Quantitative-Qualitative Translation question from the 2019 AP Physics 1 exam.  Digressions include:

* How to practice limiting case reasoning

* Two different approaches to two-body problems, with pedagogical advantages/disadvantages of each

* Why "derive" doesn't mean "show your work," it means "communicate using mathematics"

* Credit for being wrong but consistent (with good physics)

Tune in via this link.  The podcast is 31 minutes long.  The first 28 minutes discuss the rubric, but in concert with a thorough discussion of the underlying physics, the philosophy of teaching these topics, and the philosophy of awarding (or not awarding) the points described in the rubric.  If you're just looking for an executive summary of how the points were awarded, fast forward to the 28-minute mark.

16 March 2020

Physics teaching in the time of COVID-19

If you’re from the future reading this - either as part of a historical investigation into the education industry, or perhaps as documentation of the End Times - know that schools across the USA are closed for at least the next few weeks.  It is not at all clear when we will open back up.  Many of us are being asked, encouraged, or allowed to run activities online.  

I am, in fact, going to use online platforms to work with my classes.  I’ll give details in a moment.  But first, let’s discuss what’s important.

I have repeatedly made the analogy between learning physics, and playing a sport.  I consciously treat my class as a team whose goal is to learn physics collaboratively, under my guidance as coach.  I think of tests and exams the same way as coaches think of games and meets.  The AP exam (or, in conceptual physics, the thesis-defense-style Physics Fights at year’s end) compare to the state championship events.  

We have a shared understanding as a society about the importance of sports.  Sports are an end unto themselves - we care deeply about winning or losing.  And, sports are a means to an end - for example, the physical fitness habits, the social skills of winning humbly and losing graciously, serve us well beyond this year’s season.

Yet when life interferes with sport, we all understand that life takes precedence.  Sport is meaningless in the shadow of War, Famine, Pestilence, and Death.

Right now, Pestilence (and in some cases even Death) have intruded on our school year.  That means we and our students must acknowledge different priorities.  That means physics simply is not important right now.

We should not, can not, talk about how to “hold students accountable for learning.”  We should not be judging students in any way for their participation or lack thereof in our online classes.  I think most teachers are aware how some students might not have strong internet connections at home, and so will have a hard time keeping up, or that some students may themselves be sick.  But are we thinking about the students who are being asked to perform child care, or grandparent care?  Are we thinking about the student whose parent has a fever, and can’t even know whether it’s The Disease or not?  Or even the healthy student listening to their parents worry out loud about jobs and health and income and quarantine… How can such students focus on physics?  Why should they even be given the guilt trip of being asked to focus on physics at all?

But Greg, you said you are going to hold online classes.

Yes.  Because plenty of my students will welcome the diversion of physics class.  They will want the semblance of normality that my class’s time together brings to them.  They will want (virtual) human contact with their classmates, their teammates.  They will want an intellectual escape from family burdens, from worry, from fear.  I will be there for those students who want me to be there.

Principles of my approach to online course delivery during the COVID crisis.

I’m going to continue teaching like a video game.  I’ll provide a list of problems / activities.  I’ll check student work - live via videochat, or via email - so that students can either move on or try again.  Advancement along the list will hopefully feel like “leveling up.”  

I will do everything in my power to avoid assigning grades.  Or to avoid anything that could be perceived by a student as shame or guilt for failure.  Yeah, I know some of us will be required to submit grades - well, then I’d be submitting A’s for all.  Phthphth.  See above, about what’s important right now.

My school is going to create some sort of schedule, so that I can do live online class.  I’ll try to hold as much of a normal class as possible: starting with a “quiz” (i.e. a common set of questions that we all respond to individually, then find out the solutions together), then taking questions on any topic, then working on “come and show me” problems and activities.  They’ll have to show me electronically, they’ll have to collaborate via text or private videochat… my hope is that for those who attend, just being together virtually can provide comfort, human contact, and perhaps a wee sense of normalcy or purpose.

I will focus on medium-term goals.  For my AP class, I have two goals:

(1) In the Pivot Interactives video of a marble colliding with the wooden block, I ask: is linear momentum conserved?  Angular momentum? Mechanical energy?  I’ll have interested students prepare a 2 minute presentation on one of these questions.  Then, I’ll have a veteran of my class serve as “examiner” in a physics fight, asking five minutes’ worth of questions.  If I’m lucky, I’ll be able to arrange for incoming students and their parents to serve as an audience.  This will hopefully happen the first weekend of April.

(2) Continue working toward the AP Physics 1 exam in May.  These folks have worked hard all year, and most could pass the exam today with no further effort.  Most of my class will want to continue preparing, the same way a sports team would want to keep practicing for the state championship.  So, we’ll keep physics fresh in everyone’s mind, we’ll do problems and experiments together.  I’ll suggest activities designed around Pivot Interactives and The Physics Aviary and The Physics Classroom.  We’ll do old AP questions, and score them together.  We took an AP practice exam on March 5 - I’m sending a corrections packet out via mail, so they can re-try the problems they missed (and they can show me via videochat or email for feedback).

For my conceptual class, I have one major goal: the May 17 tournament of physics fights.  In a normal year, students work from late April in groups led by AP students to prepare two college-level investigations.  This year, I’ll offer to help students learn about momentum and energy - not because they’ll be tested on this material, but because their work will help them in May when it’s physics fight time.  (Students are asked to choose two of three possible problems for the physics fights.  Only one of them involves momentum and energy, so even students who stay completely away from online study will be able to participate effectively in physics fights upon our return.)

Most importantly, I will adapt as things work or don’t work.  I have no idea how a month of online-only gatherings will go.  I’ll listen to students, try new things, find out what students figure out on their own to be more useful than my online “teaching.”  I’ll be supportive in every possible way of those students who are absent or unengaged - nothing is required.

If that means a student doesn’t want to do physics, but instead wants to tell me about the non-physics aspects of their life under the shadow of a pandemic, well, it’s my job to listen.  Literally.  We are called to “know, challenge, and love” our students.  Right now most of them have plenty of challenge in their lives, so I’ve got to focus on the knowing and the loving.

14 March 2020

Jacobs Physics Podcast: Season 3, episode 1, 2019 AP Physics 1 problem 1

I've no doubt that many folks are looking for good online AP Physics review.  Well, I'm going to go through the entire AP Physics 1 exam from 2019 on a series of 30 minute podcasts.  Today, I start with problem 1: velocity-time graph and change in angular momentum for blocks on a table.  Digressions include:

* The five facts you need to know about velocity-time graphs (and you don't need to know anything else!  Really!

* My one-day approach to teaching velocity-time graphs, including experimental work

* Why you should never ask (or answer) questions during a practice AP test, or really during any test or quiz

* How to set up this problem experimentally

* When and whether you need to worry about drawing arrows at the right spot and to the right length on a free body diagram.

If you have other questions, stories, or comments about the Jacobs Physics Podcasts, please email, or post a comment here.  I'm happy to take requests for future problems to discuss!  (Send me a few hundred dollars cash, and I'll probably even record a podcast on the exact problem you're working on right now.  :-)  )

Here's the link to this season's episode 1, about the 2019 AP Physics 1 problem 1.  You might, um, notice that I called it season 4 in the opening.  Sorry.  It's season 3.

To get other Jacobs Physics Podcast episodes, go here and here and here and here and here and here.  (Or just type "podcast" in the search box.)

12 March 2020

Design: How do we convey basic information to students?

Today's post is part of a series discussing how educational design is, or is not, or can be adapted to the humanity of the end-user.  See the introductory post here.

I’m asked at institutes, how do I give students notes?  Well, I don’t.  I've been too frustrated on the user end by the whole concept of "notes".  

See, in fifth grade, I was taught to watch a teacher write information on a chalk board, then to copy everything she wrote into a notebook.  This was an important skill… in CE 1100, when transcription-by-monk was the only available alternative to the Xerox machine.

In seventh grade, I was required to make notes of what the teacher had said orally in class - with express hints like “now write this down.” This was an important skill… in the days when the teacher was the sole font of information.

Even thirty years ago, information was hard to come by.  Students had textbooks, and they were the primary and authoritative source of information.  Libraries were available to some, but even a great college library required significant effort in order to find useful references - in any subject.  The added value of a good teacher then was that the teacher had (presumably) read and investigated references beyond just the textbook, and so could deliver context and deeper knowledge through lecture.  The prize, as our headmaster stated in his first ever address to the faculty, went to the people who learned the most information.

Now, information is trivially easy to come by.  Yeah, yeah, no one can learn physics just from a bunch of wikipedia pages, but really, that’s just as useful in isolation as the old-style textbook was.  Enough good content is available (again, in any subject) for an interested student to find out whatever information they want.  The prize nowadays goes to the people who can:

     (1) sort good information from bad
     (2) assimilate what’s relevant and ignore what’s not
     (3) construct useful stories from the glut of plentiful information.

How, then, do we convey basic information to students in the most user-friendly way, while helping students with these three goals?  

Don’t be thinking in terms of what students “need for college.”  Yes, I know, some college professors require students to read antiquated textbooks, or to listen to boring lectures with badly-constructed powerpoint slides.  That doesn’t mean you should follow suit.  On one hand, you shouldn’t use ineffective pedagogy with which students are generally uncooperative merely because other teachers do - I mean, if a bunch of college professors all jumped off a bridge, would you?  But more than that, you do your student far more of a service if you show them *effective* pedagogy that they can fall back on for themselves when their future teachers are useless.  Teach them how to learn physics in a way that works for them.  You’ll find that your students become adaptable to any professor.

But, how do I “give notes?"  Think of the minimum information that students need to know RIGHT NOW, for today’s topic.  That’s what my fact sheets are for - I’ve already filtered dense textbook pages down to just the most necessary facts.  I hand out a hard copy of the day’s new facts.

Then, I have students use these facts in context.  It’s tough to memorize six different facts about velocity-time graphs.  It become easy when the class has spent an hour-long class period writing them down as they apply to different creative lab exercises.

Finally, I give regular quizzes on these facts.  Not as a “gotcha” game, but as a reminder, as a way of learning the facts through repetition and use.  These quizzes are just as effective without them “counting” in a grade book.  Give the quizzes, “grade” them, put a score on them, collect them.  If someone is consistently stinking up the joint, have them come in to redo some until they do better.  That’s good enough.  Your students will have enough background to spend most of their physics time engaged in interesting lab work and problem solving.

08 March 2020

Design: Eliminating no-name papers

Today's post is part of a series discussing how educational design is, or is not, or can be adapted to the humanity of the end-user.  See the introductory post here.

Possibly the simplest example of end-user design that I've personally undertaken in the classroom:  I was annoyed, as so many teachers are, that students turn in papers without their name on them.  What to do?

You can, as I tried one year, take points off for "no name".  What happened?

(a) Students got angry.  They didn't see the big deal.  (They also didn't have the perspective that five no-name papers in a stack of 60 caused a significant time sink for me.)  The student-teacher relationship frayed - students who already resented that I had power over them, power they only sort-of consented to, felt that I was asserting that power inappropriately and irrationally.

(b) The frequency of no-name papers did not improve.  (Students don't care about points and grades the way most teachers think they do or should.)

Once I observed (b), then my hand was forced: to continue to take off points for no name papers, knowing that the consequence did not have any effect on the issue I was trying to solve, would constitute malpractice in educational design.  It would be using the power granted to me in the classroom to shame students for being, well, people.  People as they are, not people as I want them to be.

This was the genesis of collecting assignments seat-to-seat.  Now, every paper I hand out includes a header at the top saying "Name:________________.  I collect assignments at the beginning of class while students are working on the daily quiz.  The prompt at the top of the page generally is enough of a reminder such that students write their names.  However, I also developed the habit of checking for a name as I pick up the paper.  It's straightforward to whisper - without exasperation or sarcasm - "Mr. Williams, could you please write your name here?"  And Mr. Williams does so quickly, because he wants to get back to the quiz.  Often he mouths a quick apology.  No shame.  No anger.  No strained relationship.

As I mention in the linked post, collecting assignments seat-to-seat has other benefits that address the reality of how students behave.  In particular, I know that even quite honest teenagers will not easily volunteer the fact that they did not finish an assignment.  (They generally won't lie right to a teacher's face, but they will take pains to make the teacher less likely to notice - like they'll bury a half-done assignment near the bottom of a stack.)  Collecting seat-to-seat doesn't provide the opportunity to hide.

07 March 2020

Design Revolution: the students are not the problem.

I don't know what it says about me that I'm reading books recommended by comedic soccer podcasters... but I'm reading User Friendly: How the Hidden Rules of Design Are Changing the Way We Live, Work, and Play by Cliff Kuang, as recommended on the Men In Blazers Bald Mart.

The book's thesis isn't novel to me, but the anecdotes within are.  The opening chapter is an account of the Three Mile Island incident that killed the American nuclear industry.  Kuang doesn't see operator error, though highly trained, expert operators did make errors.  He sees design error.  No reasonable person, trained or not, could possibly make sense of the 1979-era control panels with multicolored lights (different colors meaning many different things), buttons which lit when pressed even if the function ascribed to the button didn't occur, gauges in inaccessible spots requiring contortions to read.  

Similarly, Kuang delved into World War 2 plane crashes, most of which were attributed to "pilot error."  Once again, he takes issue with design, not with the people using the design.  For example, why would levers for landing gear and wing flaps be essentially indistinguishable?  Kuang cited over 400 B-17 crashes that occurred because pilots failed to deploy landing gear in an otherwise unremarkable runway approach - they twiddled the wrong identical lever, and didn't notice the mistake until it was too late.

In these and other cases, designers - and those executives making big-picture decisions about designs - exhibited what to me borders on criminal arrogance.  Why can't the idiot pilots just remember which lever to pull?  The plant operators need to RTFM.*  Let's schedule another mandatory monthly 6-hour training session so they'll stop screwing up.

* Read The Fission Manual, I think.

Does this attitude sound familiar?  If not, head down to a faculty table in the lunchroom.  Or, just as disturbingly, listen in on a meeting of school administrators discussing the failings of teachers.

Kuang's thesis is that the most useful advances in technology have come when designers have considered the humanity of the end users: not treating people as they should be, but treating people as they are.  People don't read the manual.  People push random buttons accidentally, or out of panic.  People don't remember important details in the critical moment - when in a hurry or stressed, their recall grows worse.  People react illogically and emotionally even to logical and dispassionate stiumli.

What innovations have you made in your classroom to adapt to teenagers as they are, not as we want them to be?

I've spent a quarter-century adapting my teaching to the end user, doing what seems to work rather than just what everyone says should work.  Yes, learning physics requires significant effort and engagement on the part of the student.  It's my job to help the student figure out just what sorts of effort and engagement lead to success.  It's my job to create a class culture and atmosphere that encourages useful kinds of effort and engagement.  

If Kuang is right, it's my job to optimize the design of my class for students who can and will be inconsistently attentive, emotionally prickly, unlikely to read directions... in other words, to optimize for my teenaged students, in all their humanity.  That takes enormous effort on my part.  It requires trial and error.  It requires me to be my own worst critic, asking myself regularly: is there a better way?

The next several posts will discuss adapting teaching to the humanity of the end user.  I'll tell stories of design ideas that worked or didn't work.  

My purpose is to revolutionize physics teachers' thinking, in the same way that the iphone revolutionized the entire technology design industry.  

(Oh, and the design revolution I have in mind extends as well to educational administration.  I am called to design and re-design my classes round what is in actuality effective for my non-ideal students.  Administrators should feel similarly called to design faculty meetings, development/evaluation programs, and all administration-teacher relationships around what is most effective for supporting teachers - in all their human foibles.)

04 March 2020

I'm a "Come and Show Me" teacher.

I'm not a Sit-and-Listen teacher.  That doesn't I never talk at students from the front of the room.  My class grades daily quizzes together, while I explain the solutions.  Occasionally in the AP class - probably once per week early in the year, though essentially never in conceptual physics - I do a quantitative demonstration from the front of the room.  But that's it.

After the daily quiz, I give students a list of things to do, usually involving prediction and measurement in the laboratory.  Sometimes the list includes test or quiz corrections.  Sometimes a Pivot Interactives video or a The Physics Classroom concept builder make the list.  

Whatever the activity, students are released quickly from the responsibility of paying attention to the person in front of the room.  That's more important than the majority of teachers realize.  See, you get antsy sitting through an hour-long faculty meeting - you consider a three-hour district professional development presentation your personal purgatory.*  How do you think students feel as they are shuttled among seven different sit-and-listen classes with minimal breaks in between?  And they do this every single day?

*The sale of indulgences would create a significant revenue stream.**

**Shh, Greg, don't give anyone ideas, dangit.

Okay, many physics teachers do in fact leave plenty of time for their students to work independently on some of the tasks I've described above.  What do you do while they work?

Some teachers walk through the room giving advice, encouraging questions, helping to debug lab equipment.  That's fine.  I know some amazing teachers who are always on their feet through the room.

I don't walk.  I sit at the front of the room.  Students are asked to bring me their work after each problem, after they have acquired data, when they've reached a defined check point.  

At last week's AP workshop, Glenn experienced my position-time graph exercise. "Oh, so you're a Come and Show Me Teacher," Glenn told me.  Yes, yes I am!  I had never heard that term, but I love it.  

The advantages of Come and Show Me go beyond merely avoiding student ennui.  Students physically moving around changes the dynamic of the class.  It makes the atmosphere far more similar to a coffee shop than a library.  And where do students generally choose to work these days?  The Panera in University City, Philadelphia on Friday afternoon was chock full of students studying, to the extent that a seat was hard to find.  I wonder ironically whether the UPenn Library was similarly packed...

The Come and Show Me class style encourages students to talk to each other about physics - since I'm not within easy earshot of each student, and since I've generally got a line of people waiting to talk to me, it's much more effective to ask a friend rather than me if a student has a quick question.  Come and Show Me avoids noble-yet-fruitless staring at problems without making progress, or charging though a problem for most of an hour compounding mistake upon mistake.  Instead of finding out later that their approach was all wrong (and then being frustrated with the wasted time that can't come back), students get feedback sooner rather than later.  But Come and Show Me explicitly discourages students from relying on me to answer every little question, to do all the heavy lifting for them.  Just the obstacle of having to get up and walk to my desk, then to stand in line for a minute or two, encourages everyone to work out whatever they can for themselves.

To use this style of teaching every day requires significant culture building early in the year, a large and diverse set of exercises for students that include things to come and show me... and enormous confidence on the part of the teacher.  Confidence that the class, for the most part, will adapt to this very different approach to learning.  Confidence that when a couple of students don't adapt, your style is still serving the vast majority of the class well.  Confidence that when you hear passive-aggressive comments from parents and colleagues ("You didn't go over this, I don't know how anyone is supposed to understand." is the most common), you should nevertheless carry on. 

Don't listen to early feedback.  Listen to what people say at year's end, and especially to what they say 1-5 years later.  

What I hear years later is that my students don't remember every detail of each of Newton's laws.  But they do remember how they felt in class - they looked forward to my class.  They remember the relaxed and friendly atmosphere.  They remember their pride when they finished each listed item and moved on to the next.  And they remember that there was no room for BS, no room for half-measures in solving physics problems: since they had to show me their work right then, in person, with a line of people behind them... they were careful to put forth truly their best effort.