Day 11 (Monday):

The take-home message today?

Intensity level is a scaled value for sound while sound intensity is more of a raw value for sound (dependant on its frequency and amplitude).  And, while intensity can be calculated from physical properties of the source, most references to “intensity” in everyday usage are really referencing “intensity level.”

We worked a problem as an example going back and forth between the two (intensity and intensity level).  [If one child is "loud" at 75dB, how loud would a room full of 30 children be?]  This activated a standard.  So all in all, a productive day.   This does lead to a question to others doing SBG:  what is the average rate of activating standards?  One or two per week?  One or more a day?

Day 12 (Wednesday):

We discussed Doppler effect today.  For a break in pace, we first discussed how Doppler radar works in an important everyday example (everyone in OK knows about Doppler radar–access to weather data and imaging in this state is phenomenal).  Increasing/decreasing distances between reflected wavefronts off of a distance cloud is a concept students grasp well, so I went with it.  Then the equation(s) were put up on the board for determining the observed frequency.  I like combining the expressions with a +/- in the numerator and a -/+ in the denominator.  General rule: choose the upper sign for approaching and the lower sign if motion tends away from the other.  We worked a couple of examples, then I gave a more challenging/conceptual question:

If you are swinging a buzzer at the end of a string in a circle with a constant angular velocity, what would the observed shifte frequency as a function of time plot look like?

To force students to consider a scale on the plot, I gave values for the angular velocity, radius of the circle and the frequency of the source.  A curious feature of this problem is an unexpected hangup students had (and I should have anticipated it): confusing the angular frequency $\omega$ = 2 $\pi$ f of the swinging sound source with the frequency f of the sound coming from the source.

Anyway, long story short: after all was said and done, all of the standards were active at the end of class.  I’m getting excited about moving on to new material–now I just have to polish up the new standards!

Day 13 (Friday):

Pop quiz again!  This time we looked at a video:

.  The question was,

For which segments of the film loop are depictions of the Doppler effect accurate and innacurate?

I’d intended this to be a real quiz, but we ended up talking about it as a group discussion.  It turns out students could answer it pretty easily, but even they recognized that they’d never really questioned sound effects like this before.

We then began electrostatics, using some PhET simulations as an introduction.  It’s amazing how much content can be pulled from the balloon and John Travoltage sims!

Day 7 (Monday):

We closed out Chapter 15, activating the last remaining standard.  In hindsight, there were some “neat” things we didn’t do in this chapter (derivations and a few extra demos).  But in the interest of time and really trying to focus on the standards, they simply didn’t make the cut.

I also haven’t given a pop quiz yet.  That will happen next class, maybe.  As the time I thought was right for a pop quiz today, we ended up using it as a mock assessment.  I drew two wave plots on the SmartBoard and asked them to write the corresponding wave function.  They were also supposed to include values for amplitude, period, wavelength, wave number and periodic wave.  After going over the answers (which were on small whiteboards), it was clear no one would have gotten a “3″ or a “4.”  Students agreed that the scores earned would have been a “2″ or “2-ish.”

Day 8 (Tuesday):

Today (in lab) we pulled from Chapter 15 a bit to serve as an introduction to sound traveling in an air column. While a string under tension is different from sound, the expressions for the normal modes are the same for strings under tension and sound if both ends of the sound column are open or closed.  So I started by drawing diagrams of the standing waves for both ends closed (string and sound); noting nodes at closed ends, antinodes at open ends.  We derived the expressions for the normal modes and showed they were equivalent.  Then, a series of diagrams of sound tubes with one end open, one end closed revealed we’d need a different expression where n = 1, 3, 5, . . . applies, rather than n = 1, 2, 3, . . .

And <pouf!> Standard 16.4 (a lab standard) became active.

To demonstrate how sound consists of a source undergoing vibrations, I showed the second half of this YouTube video:

It’s worth watching, and it has a little bonus at the end about filming rate.  I wish the narrator made reference to beat frequencies as an analogy to what is being observed (f_ beat = f_tuning fork – f_filming rate|).

Anyway, the task for students in this lab was to determine the speed of sound empirically given two tuning forks of known frequencies and the apparatus below:

Jokes and confusion ensued as everyone fumbled around with how the 2nd normal mode is the 3rd harmonic and the 5th harmonic is the 3rd normal mode, etc.  Kind of a “Who’s on 1st” banter.

A student mentioned having seen a video of a series of pendula showing neat normal modes.  I knew just the video he was talking about:

I made the comment that constructing a demonstration like this (having determined string lengths and normal modes ahead of time) would get a 4/4 on one or more standards

Day 9 (Wednesday):

Well, I forgot the pop quiz.  Again.  Good thing these posts aren’t published until the week is over!  Pop quiz to be given on Friday, maybe

Spent time today on wave interference.  Having two large tuning forks attached to wooden rectangular boxes (with one end open) really helps demonstrate how one wave can drive another.  Adding a movable mass to one of the tuning forks illustrates beat frequencies well, too.  One student brought up tuning instruments in band, trying to hear the beats everyone was talking about.  A perfect example from previous experience to tie in to class!

Discussion of Bose sound systems, noise cancellation features of automobiles and noise cancellation headphones led us to working a problem involving two speakers creating interference for an observer some off-center distance away.  Having reasoned out the relationship ahead of time, we found a typo in the textbook’s example.  (f = nv/d where n = 1, 2, 3, . . . for constructive interference; f = nv/2d where n = 1, 3, 5, . . . for destructive interference).

While it wasn’t announced today in class, this essentially activates Standard 16.2.  I’ll have to announce it officially in Friday’s class.

So is it ok to activate standards out of sequence?  I think the answer is yes–at least that’s what’s happening this semester and the flow of the course doesn’t feel weird, anyway.

It just seems natural to talk about beat frequencies immediately after addressing and working with normal modes of waves.  We’ll get to intensity and intensity levels soon enough, just not in the order Young & Freedman have it printed in the text.

Question: I know that you can sustain hearing damage if subjected to intense sound, even if out of the audible range.  However, if you are wearing noise cancellation headphones and there is a very loud sound they are cancelling out by producing waves that interfere destructively, are your ears more susceptible to damage by receiving a pair of out of phase sound waves?  Or, does the cancellation really mean a decrease in vibrations received by the ear?

Day 10 (Friday):

Well finally, Friday arrived and I remembered to give the pop quiz!  The problem was given at the board.  No numerical values:

You walk in front of a concert stage with two speakers at either end (separated by a distance L).  As you walk from in front of one speaker to in front of the other speaker (parallel to the stage), plot the volume of sound you would hear as a function of L.  Assume the speakers are emitting a constant tone of the same frequency.

I’d secretly planned to ask a student to come to the board — just hoping for a 3 or a 4 performance for our first standard.  And we got it!  By the end, we were all chiming in.  And the diagrams drawn by the student were pretty thorough, addressing:

• Interference patterns if the tone emitted were perfect and no other interference/reflections were occurring
• Interference patterns if the speakers were playing music with multiple tones
• Correct scale in terms of L as to where minima and maxima would occur
• What the idealized interference patterns would look like if the frequency of the tone were increased

There are a couple of points I’d like to make as to why today’s class made an impression on me and my students:

1. At the beginning of class, someone said “No one likes pop quizzes” <shaking head with a quiet groan>.  However, it soon became clear that quizzes are (in this class) an opportunity to submit a standard.  And hey, if you don’t do so great, then you can learn from it and resubmit.  The pressure to perform was alleviated.
2. If someone is absent from class and misses the quiz, that just means they’ll just need to submit that standard on their own.  Students will likely share what they did in class during the absence

Anyway, I had to leave campus early in the afternoon, so I wasn’t able to get a screen capture of what was done in class to post and share.  But that’s what I wanted to do, to brag about how the discussion went and how well questions were fielded; all of which is the subjective litmus test for assigning it a 4/4 (per Andy Rundquist!).

Most of this entry is just journalling.  SBG stuff can be found toward the end.

Day 5 (Tuesday):  Clothesline Lab

(Monday was MLK Day)

The short of it: what we did in lab today addresses Standards 15.2, 15.4 and 15.5.  Not in entirety, but quite a bit of each.

Lab began with me drawing a picture of a standing wave on a string on the board (y vs. x).  I had the students tell me what the measurable quantitites were.  Amplitude, wavelength, # of nodes and one student even got at linear density of the string.  I was impressed!  Replacing one end of the system with a pulley, it became obvious tension in the string was an additional variable that could be measured.

I have to admit, I did some handwaving about how the velocity of a wave on a string is dependent on tension and linear string density.  But knowing the derivations is not really an important part of the standards.  It’s an example of how really neat derivations can be good exercises, but not critial for understanding the course content as a whole.  This SBG approach is really pressing me to trim the extras so we stay on task.

Following a brief introduction of waves on a string, students were introduced to the CENCO string vibrator.  They were then tasked with collecting enough data to write out a wave function

y(x, t) = Acos(kx – ωt).

The catch: the frequency of the string vibrator had to be determined from a plot of wave velocity versus wavelength (the slope yields frequency).

Application exercises included writing out y(x, t) for x = 0 (pretty straight-forward) and confirming whether or not the location of the nodes are consistent with their wave function (not so straigth-forward, since x = 0 is problematic).  I hope my students recognize that since the system is symmetrical, they can measure x from the node at the pulley rather than estimating it from the tab.

Day 6 (Friday):

Announced that the lab standards (there were 2 of them) were now active.  This was after a discussion of lab and average power of a wave on a string.  I did not spend much time on the derivation of the equation, but did refer back to the relationship of power in terms of force and velocity.  From there,

P = F v

P = F(x, t) v(x, t)

I made loose reference about how there were steps involving calculus lingered in arriving at F(x, t) and v(x, t).  I don’t like handwaving explanations, but the steps are outlined pretty clearly in the text.  Instead, we used data collected from lab to investigate something I’d noticed “kind of” in the past, but became more clearly defined in Tuesday’s lab.

Students noticed that the amplitude of standing waves on a string varied: the greater the tension, the greater the amplitude.  It wasn’t huge, but enough to be noticed.  So, we calculated the wave number and periodic wave for four separate standing waves.  We then calculated the power associated with each and plotted power as a function of tension (for a stretched wave on a string).  I was honest with students and told them I’d never plotted this before, so wasn’t sure what to expect (linear vs. non-linear trend).  It turned out to be fairly linear, however a third order polynomial seemed to fit it pretty nicely too.  But with only four data points, we decided we’d like to see this done for more data plots. . . maybe one of them will take the initiative (hint, hint!).

The good news is, all of this was directly related to the lab standards.  Solving problems involving the normal modes of a string under tension and the wave’s average power.  On a side note, I am really looking forward to weeks where there aren’t interruptions in the class week (days off, sickness, etc.)–the next few should be pretty solid weeks.

SBG Chat

Students commented that they were excited about SBG.  They thought the work load was going to be more at first.  However, once they started understanding the material and fully reading the standards, they saw how the standards could be address with a thorough problem.  In each of my standards and recommended assignments, I list a “The Point” sentence.  In this statement I come clean about why I’m asking them to do that standard.  In part this is an open way of being accountable for what I assign and justifies the work (no, it’s not just “busywork”), but it’s also a pretty overt way of being transparent with students.  This works well with my calc-based physics students since they are engineers and like to see the applications/worth of things.  I don’t know if students in other classes would appreciate it as much.

Day 1 (Monday):     Syllabus review and Screencastomatic

In all fairness, I hinted to my students at the end of last semester that there were changes coming this spring, so they new something was up.  Still, I thought things went pretty well.  They liked the idea of always being able to improve their scores on the standards.  There was some interest/concern over the screencasts and the ways that standards could be submitted.  As this is the first go of things, I have to admit I’m interested to see how it is all going to work out, too.  I anticipate questions as soon as the first standards become active.

Demonstrating how Screencastomatic works seemed to help the mood of things.  Students were more at ease knowing that this application ran without requiring an install.  Plus, our lab has a SmartBoard and I told my students they could use it if they wish.

I emphasized my reasons for the shift to SBG (previous post) and that since was new to all of us, I’d be seeking their thoughts on it throughout the semester.

Day 2 (Tuesday):     Notes and demos instead of lab

Because Day 1 was consumed with syllabus, SBG discussion and a screencasting tutorial, today in lab we forged ahead with notes and demos.  Also, I have a meeting in OKC on Wednesday, so notes during the first lab was an intentional preemptive strike to stay on target.  By the end of things, standards 15.1 and 15.2 became active.  Class ran pretty smoothly.  I found myself referring to my list of standards more than my notes/text.

Class/lab began by collecting data with a Vernier sensor and looking at a y-position time plot of a hanging mass.  We were able to get a sense of what simple harmonic motion “is” (tough those words were not used).  Discussion of the data led to identifying what physical properties could (and could not) be determined from that kind of plot.  Then we looked at the Columbia Wave Machine (ca 1908, sporting its infamous “ether” waves!).

Also demonstrated the Air-Zooka.  I leveled with students and told them that I used to think it generated solitons, but am now pretty convinced its just a wave pulse.  If any of you readers have input on that tidbit, I’d appreciate it!

At the end of class, two students visited with me for a while about SBG.  Overall, they are interested in the concept.  One is even excited at the idea.  Though they are not convinced I’ll be able to keep up with all of the standards and the active times per student across all standards for the entire semester.  Can’t say as I blame them–I’m really going to have to be a better accountant of dates, due dates, assignments, etc.  The suggestion came up that the number of resubmits be limited to three times or so.

At the beginning of the class, I visited with students about this blog.  I asked for their permission to write about our experiences as a class.  They were ok with it, so it looks like I’ll give it a shot.  So long as I don’t get to swamped with things (or too wordy with posts!), I’m going to try to continue this open journal for the duration of the semester.  Last year my physics road signs got off to a great start but then died off.  I could have said it came to a Dead End, but that would have been a pretty lame joke . . .

Day 3 (Wednesday):     No class, students to brainstorm about their semester projects

Day 4 (Friday):     Example problems and SHM wrap-up discussion

Discussed the differences between systems that are periodic and those that exhibit SHM.  Also discussed damped vs. driven systems.  Most of this was conceptual.  A question of the standards came up: can examples used in class be submitted for standards.  Short answer: No.  Some background . . . one of the standards requires students to provide two examples of systems exhibiting SHM and two other examples of systems that are periodic, but do not exhibit SHM.  We talked about pendula, the infamous cat clock pendulum, a bouncing ball and a PASCO cart “bouncing” back and forth on a track.

Consider a system that is imaged by an open camera frame and a strobe light.  How would the object be imaged on the film?  Would this be representative of a Hooke’s law type force?  (x, v, a as functions of t)

We derived the velocity and acceleration expressions for the general wave function.  No big deal, just two derivatives.  The representation: (xt) = -Aω² y(xt) took students a moment to assimilate.

I feel as though I could have armed them more for tackling a standard.  ”Discussing” and talking about plots of these functions is different from having them generate/look at real data themselves and function fit.  Classes earlier in the week were more meaningful than today’s, I thought.  With no class Monday due to holiday, we will have to spend lab on Tuesday looking at wave functions so they can see applications of this stuff.  Wave function for a vibrating string under tension???

SBG: With A Little Help From My Friends

With some encouragement from colleagues, I’ve decided to try Standards Based Grading in my second semester calculus based physics class this spring (2013).  Because this is my first attempt at SBG, I leaned heavily on the work already done by others and their advice (namely Andy Rundquist and Frank Noschese).  I also gained some instant supporters through Twitter.

So I don’t bore readers with all of the finer details, I’ve tried to break up my thoughts by headings below.  Feel free to skip around, and if you make it to the end, this post will end up in that discrete minority of entries that are read in entirety!

Motivations

Change for change’s sake was not enough to warrant this shift in assessing my students.  And, while trying something new can be refreshing for the instructor, there is more to the story here.  I really am looking for ways to make the course more meaningful for everyone.  And there were some very specific items I wanted to address explicitly

• Assignments up to this point have always been one-time “values” students earned.  If students made improvements later on in the course, traditional grading means could not facilitate “master learning/grading” (revisions of grades due to addressing shortcomings in resubmissions).
• While I could in general understand the reasons for choosing certain assigned problems, specific objectives were not clear to students.  And, to be honest, choosing end of chapter problems was not as focussed as I would have liked.  When choosing problems, I found myself thinking:
• “Yeah, they need to do one of those; it’s kinda out of the box” and
• “That’s a classic problem, they need to work that one out”
• These rationales are subject to just being assigned on a whim, which may change by the mood the instructor is in.
• I loathed deciding how much each problem was “worth” point wise.  About the only thing I standardized was 0.5 points off each time units are incorrect/omitted.  Partial credit consisted of my inferences on where students’ thought processes were misguided.  Longer, more difficult problems were worth more points; shorter single step problems were worth less.  While this makes sense at the surface, I began to question “should credit be based on content tested rather than length/difficulty?”
• These students are pre-engineering students.  Eventually, they will need to present their ideas to their colleagues and clients.  Presenting ideas and explaining your own thought processes are fundamentally different from simply turning in a problem set and being done with it.

Apprehensions

With just about anything new, there is an uneasiness that, well, makes one feel uneasy!  The following are my greatest apprehensions.  Time will tell how warranted they are.

• One way students will need to submit work for standards is by screencasts.  I’m just beginning to create screencasts myself and know there’s a bit of a learning curve.  Much of the burden will fall on the students here, but there are some wonderful pain free ways to create them.  Screencastomatic is quickly becoming one of my favorites.  Jing is what I learned on.  If the means to create them requires admin privileges, it could be a show-stopper for some of my students.
• A departure from traditional instruction might not be received well by the institutions these pre-engineers transfer to.  However, I reasoned that if students are more thoroughly grasping the most important concepts in physics, are future instructors really going to care how “assignments” were graded?
• I couldn’t break completely free from the last bullet.  I’ve kept exams a part of the course, though they are take home exams.  There is also a separate lab score.  Some standards can be addressed with what is done in lab.

The “Points”

Standard grading is on a 0 – 4 point scale: from 0 = no attempt to 4 = exceeding expectations.  Essentially, I’ve used the rubric Andy Rundquist has on his course website (where he credits Frank Noschese).  I  added the element of “able to come up with examples and applications outside the context of the problem” for a 4.  Because I wasn’t sure exactly how many points there would be for the entire course, I decided to use weighted percentages for the different course components:

 Standards n 40% Laboratory Reports ~10 10% Exams 4 30% Final Exam 1 10% Project 1 10%

Full Disclosure To Students

I really wanted to be transparent with my students.  Too often, I think they feel in the dark about why they are being asked to solve certain problems or required to do this and that.  So below is an excerpt from the list of standards to be handed out to students.

This is what students will see:

Chapter 15: Mechanical Waves
Standard 1
I can successfully compare and contrast different types of waves, periocidy of waves, sinusoidal waves and provide a clear & complete definition of simple harmonic motion.

Assignment:  (Recommended and required for submitting reassessments)

1. Describe two different examples that are periodic but not simple harmonic oscillators.  Describe two different examples that exhibit simple harmonic motion.  Include sketches/graphs for each.  (Use multimedia for source material if you wish, like YouTube).  Of all of these examples, explain why some are and some are not SHM.
• The point: periodic behavior does not necessarily mean it is SHM!
2. There are many types of waves.  Give explanations of the three basic types discussed in Chapter 15.  Research a fourth different type of wave.
• The point: some waves can be described as combinations of other types of waves.  Other wave types or “wave-like” phenomena are completely independent of others.
3. Text problems 15.3 and 15.5
• The point: “periocidy” means we can use basic physics to get at the basic physical properties of the wave.  But there is a lot more to the story . . .

I heeded the advice I read in Andy’s blog and those who left comments: Standards become “active” when discussed in class and students then have 2 weeks to submit their work.  If they want opportunities to resubmit work, then they need to submit the recommended assignment in the same time frame.  From then on, they can continue to resubmit so long as the standard has been active within 2 weeks.  I’m a little fearful of the accounting this will require, but it’s a small class (only 3 students!).

Other advice taken was to have the policy that score may go up or down based on repeat assessments.  I think higher ed courses can implement this more easily than K-12.  I just hope students see the merits of this policy.

Students can submit work for standards in various formats: screencasts, URL’s of appropriate media supplemented with their own written narrative, office hour visits, class quizzes, class discussions and chance/water cooler meetings.

Well, that’s it for now–this ended up longer than I’d anticipated.  Thanks for reading!

The best kind of profession permits you to carry out extra curricular activities you enjoy without acting as a diversion.

While at a conference recently (AAPT), I was presenting material over an astronomy workshop I’d held with a colleague during the summer of 2012 (at the SLL Observatory). The poster had the usual stuff on it: pictures of the facility, demographics of participants, bulleted lists of what we did, etc. And, even though it was located off the beaten path from the bulk of the posters, it got a lot of traffic — no complaints here.

Those who stopped by to visit had great comments and questions. And then it happened, on more than one occasion… I felt like I was out of the loop; like I’d missed some memo on current buzzwords. I was asked by several individuals

“So what mileage did you get out of doing this?”

To be honest, I didn’t know how to respond at the time. The truth is, working with an NWOSU adjunct who is also a member of a local astronomy organization (Starcreek Astronomical Society), we simply came up with the idea while stargazing as something that would be fun to do: apply for a small grant to host an astronomy workshop in rural Oklahoma. (It was a great success, by the way!)

Anyway–since then, I’ve had time to reflect on the question and its broader meaning. Turns out, it’s an incredibly valid question! and we should all consider answering it before taking on a new project or saying ‘yes’ to the next extra curricular activity around the bend.

When it comes to deciding what to do and why, here are two basic factors to consider:

1. Your professional activities ultimately play a role in things like job security, promotion and tenure.
2. Extra curricular activities require additional time and will draw from your resources.

While fun and interesting, item 2 above can mean time away from family and hinder fulfilling what’s wrapped up in item 1. Plus, saying “yes” to too many things means you may not be able to complete any of them to the quality you’d like. Not to mention more involvement in things means less “power down” time for you (we all need a little separation from work!).

The best situation one can find oneself in is one where items 1 and 2 above are aligned. Extra curricular activities don’t have to be an added drain/strain. They can be framed in ways that augment the experiences of more than those they were designed to benefit directly.

For example, I help host a local robotics competition (BEST) and and am often asked to launch rockets or do a science demonstration day for area schools. With a little bit of lead time, I get my students involved as much as I can. They help run demonstrations on science safety, judge at the robotics competition and play a role in getting the rocket fleet up and running. And I’m not just pawning off my work to students! Many of them are pre-professional students or future teachers: they need community-based volunteer experiences and public school field experience hours to round out their undergraduate programs of study. In fact, our science majors must complete Science Fair Judging: a service-learning course designed to help majors see the merits of professionals promoting/supporting STEM initiatives among youth. The science fair “extra-curricular” activity has turned into a benchmark experience for all of our majors (biology, chemistry and science education).

The mileage I gain from activities like these is not just in helping students complete their degrees or resume building. One of their most critical values is maintaining relationships and continuity with area HS teachers/schools. This has been a tremendous asset in feeding grant-funded professional development opportunities (see ToPPS, for example).

Long story short, the odometer may not be easy to read in all that we do, but if we keep our wits about us and heed our colleagues’ advice (like backseat drivers!), we’re likely to stay on the right path. And those extra curricular activities? They aren’t always exits away from your final destination. . .

The Physics Round-A-Bout

If you’ve ever been in a physics class, at some point you know it’s going to happen. Sometimes it’s once a week– in other classes it’s every single day.

Teacher: “So we see here, there’s a system that looks like this . . .”

Students: Nodding, acknowledging they see what she/he is referring to.

Teacher: “Ok. Now what will happen if I do this?” (Motions like she/he is going to do something to the system but freezes for drama and to prompt some student reactions).

A multiple choice question pops up on the screen, asking for students to make a prediction of what happens next.

Students: Wrestling with what to say/choose, begin working through a mental flowchart; a newly established norm for physics class that defines how they approach answering “simple” conceptual questions:

1. “Nope, it can’t be that one, because that’s the obvious answer–that’s too easy to be right.”
2. “It could be that answer because it’s the opposite of the obvious answer.”
3. “It’s best to choose one of the other choices because by default, the other two are what the teacher expects me to choose based on what we know (or don’t yet know).”

For the sake of the physics education road sign theme lately and keeping things simple, I’m going to call the above logic/graphic the Physics Round-A-Bout (though I know it happens a lot in other disciplines, too). It’s based on every teacher’s desire to surprise or impress upon students something that is unexpected.  Let’s face it, for the most part teachers like sharing what they know, and teachers are intrigued by counter-intuitive explanations.  This in large part is what is responsible for the physics round-a-bout.  But the round-a-bout is also partly derivative of learning theory: by creating a discrepant event, disequilibrium or cognitive dissonance among students, students begin to assimilate the new information until it is accommodated within their world view or mental content. Wait, what? Yeah, sorry about the jargon . . . Those familiar with Piaget’s work, the work of Karplus or Strike and Posner’s conceptual change research may be giving a fist pump right now. For the rest of us, here’s the short of it:

You see something that doesn’t make sense. You are perplexed. So naturally, you try to figure it out. You work at it until you arrive at some kind of explanation that makes sense to you (whether accurate/complete or not)– fitting it in with other related stuff tucked away in the back of your mind (sometimes done consciously, sometimes not). Then you feel at ease, ready to move on to other things.

This works, and it works well.  Humans engage in this practice since birth and it plays a significant role in how “science” is carried out everyday. In fact, science education research and practitioners have formalized the process and put it to use.  The 3-phase learning cycle, for example, is designed around it (the 5- and 7-phase LCs include assessment and “engaging” elements).

The problem is, when we teachers repeatedly set up lessons or demonstrations to spark interest and get students perplexed or to make predictions, we often do so without first giving them the opportunity to build a knowledge base to adequately tackle the question. So students frequently are not well-equipped to address what’s presented.  And they fall victim to this teachers’ traps time after time.

Short version: We teachers routinely set students up to fail in making predictions, and it gets old.

At an AAPT meeting, I recall a presentation on this by Eugenia Etkina.  It was some time ago, but it left an impression on me since I’d already begun questioning the “sage on the stage” teaching mode.  For further reading on this, this article by Eugenia Etkina on ISLE provides a good background, though the document covers much more than what this post is about.  Fast-forwarding to page 26 of the document gets right to the point: repeated conflict, confront and resolve teaching strategies may actually hinder learning.  Instead, there is evidence that students may stand a greater chance at remaining tuned in to the content for long term understanding if they are provided with experiences/data to make successful predictions.

When you think about it, it’s pretty obvious: Do you like being accurate or well-informed about what you’re talking about, or do you prefer to always be corrected on your talking points in front of your peers?

So for me, this doesn’t mean “out with all the demonstrations.”  It means letting students ask questions and guiding them toward looking in to key factors that will help them make informed predictions.  Still show them cool stuff; everyone likes a surprise/change of pace every once in a while.  But try giving students the opportunity to see the connections and applications to the material before an eye-catching demo.  Engage them with content they can wrestle with and avoid routine magician shows that always have an unexpected result for unsuspecting physics students.  Because in the end, it may not end up getting them anywhere but further removed from the discipline.