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19 May 2011

Don't neglect "review" for lower-level physics exams

Young fool... only now, at the end, do you understand.
Those of us who teach AP physics have gotten used providing an extended review for a difficult year-end cumulative exam.  Conversation with AP teachers indicates that anywhere from two to six weeks is generally reserved for review.

I understand that "review" is often a pejorative term.  In fact, I was advised years ago to avoid that term entirely, lest ignorant colleagues question my usefulness -- "He stops teaching six weeks before the exam to review, so why should the students bother to go to his class?  They should skip physics lab and come to AP history class, where we're still learning new material all the way until mid-May.  And we should give him hallway supervision duty because he's not teaching, anyway."

I renamed this segment of the year the "putting it all together" unit.  For that's what we're doing:  not merely reminding our students of topics we haven't explicitly covered since October, but showing how all topics interconnect.  A good physics problem integrates two or three disparate topics, asking students to make connections.  Only in April, after we've finally covered everything in isolation, can we truly show our students these connections.  Furthermore, students rarely learn a physics topic well the first time they see it.  The second and third time, though, techniques and concepts become old hat.  So correct pedagogy requires that we introduce projectile motion in September, and move on; we occasionally do a projectile motion problem as we introduce bernoulli's principle or parallel-plate electrostatics; and, most importantly, do a homework problem in April on projectiles again.

I'm not telling AP teachers anything they don't know already.  I'm posting this with regard to lower-level physics classes.

I disagree with the typical approach to tests and exams in a general-level physics course.  Tests in the second part of the year often explicitly exclude force and motion topics from the beginning.  (I find "unit tests" to be common, and also nearly useless as a teaching tool.)  Frequently, the "final exam" becomes merely an expanded unit test on the last couple of topics.  These are not authentic evaluations of physics skills!  If we want our students to remember physics, we must continue to require them to recall basic concepts, even from the kinematics we covered last September!

I move very slowly in general physics, certainly in comparison to AP.  That's all the more reason to make every test cumulative, like I do in AP.  Early in the year, this is not a problem.  As the year progresses, and force/motion topics were covered longer ago, I find it more critical to do substantial review before each test and before the final exam. 

Through the month of April, my regular class covered optics -- waves, light, snell's law, lenses, and mirrors.  On the test in late April, I explained that the multiple choice would be exclusively these topics, but the "justify your answer" and "open response" sections would be on topics distributed throughout the year.  As preparation, for two days before the test we worked on a 60-question multiple choice practice sheet.  I set the sheet up as a game: we worked in randomized pairs, where each pair was awarded points not just for getting questions right, but for getting the DIFFICULT questions right.*

*The exact scoring was one point for each correct answer, and one additional point for each other group that got that answer wrong. This provides a disincentive from the class all relying on a single student to distribute the answers.


In the event, students performed better on this test than they had all year.  Only one student out of 22 earned less than a B.

I just tried the same approach again for yesterday's test:  multiple choice focusing on astronomy and optics, with the rest of the test cumulative.  We did a similar review exercise.  This time, though, about a third of the groups didn't take the review as seriously; we performed well on the test, but not as well as before.  There was a reasonable correlation between scores on the review multiple choice exercise and on the test.

The final exam is coming up in two weeks.  I'm not covering any new material.  Instead, we will build an AM radio, and continue AP-style review of the year's work.  I want to encourage preparedness for the general physics cumulative final exam the same way I do for the AP exam.

Do you teach a general-level physics course?  Do you have any general physics review ideas?  Post them in the comments.  I just might try out your idea next week.

GCJ




2 comments:

  1. We do a lot of test-like questions using clickers & peer instruction. There is a high level of engagement when the clickers come out. But they love playing jeopardy the most. I posted my electrostatics & circuits jeopardy along with my rules at: http://tarshisphysics.wordpress.com/jeopardy/

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  2. HUGE fan of having all assessments remain cumulative throughout the year. I just love when students ask "what's on the test?" The response is always easy... "anything!"

    We do a number of practice exams, with students self-scoring their work on individual topics, then focusing on the lowest-scoring topics before repeating. Our first practice exam is done open book, in teams. The second is open book, individually, and we'll finish up with an individual closed-notes practice exam. Again, after each iteration, students self-score themselves and devise an individualized action plan to improve their scores.

    Of course, this can quickly become tedious, so we break this up with some "multi-unit" labs such as a conservation of energy lab that touches on kinematics, dynamics, momentum, impulse, and conservation of energy; a rocket project that hits on many of the same topics, and some jeopardy-style team review games.

    More details on the nuts and bolts available at http://bit.ly/mb7B4f

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