Kamis, 07 Februari 2013

Adapting "Quantitative Demonstrations" to 9th grade conceptual physics

Most regular readers have seen that my primary method of instruction for junior-senior courses is the quantitative demonstration:  rather than just solving a randomly chosen example problem from a text, the example problem is set up experimentally in front of the class.  The "example problem" instead becomes a testable prediction of the result of an experiment -- and the prediction had better be accurate.

I realized pretty quickly that 9th graders don't have the attention span to run quantitative or qualitative demonstrations as a class.  My demonstrations by themselves are not particularly interesting; they only become beautiful because of the prediction made beforehand.  If the students can't focus long enough to understand the prediction, the demonstration is useless.

One effective method with 9th graders is to set up a homework or quiz problem as an in-class demonstration -- if you've got them taking the homework seriously, then the in-class verification of the correct answer can be useful.  But they do need guidance in how to actually solve the problems -- that's why I do the problem solving in class for juniors and seniors, because I'm modeling the correct approach to homework and test problems.

So I tried something different with the 9th graders.  I handed out a page with an example problem to work through in guided fashion -- that is, I asked leading questions for parts (a), (b), (c), etc. so that they could generally finish the work individually, if at a variety of speeds.  When they finished, they showed me.  If the answer was not clearly justified with appropriate facts, equations, or calculations, I made them do it over.*  Each person gets a different problem, or at least a problem with slightly different inputs, so that it's okay for people to work together -- mere copying won't help, only collaboration.

* In the eternal fight against numerical answers without units, I've accidentally discovered an excellent weapon.  The method described in this post necessitates a line of students who are waiting for me to check their work.  Instead of the punitive "-5 points, no units" I can instead say, "whoops, no units, back of the line."  Not only does that particular student feel sheepish, every other student in line quickly checks his own work for units.

Then, when I approve a student's work, I tell him to go check it out.  In the back of the room, I've set up the experiment for each of the four or so example problems.  The handout instructs students to measure and record the result; they bring the experimental evidence to me, usually in the form of an ipad picture of the reading on a labquest.**

**I can't get my labquests to print, but I have a class set of ipads.  Photographic evidence of their experiment is good enough for me.

As linked above, the google doc with four Newton's second law problems is here.  Read and comment to me, please.

Many of you will probably note that this is as close to pure "modeling" as I've ever come.  Some will call this process "discovery" or "inquiry".  Some folks this summer discussed "stations" with different experiments.  Sure, this sort of approach to physics class is hardly new.  I've tried it before, but I found general-level juniors and seniors to be unwilling and unenthusiastic participants in these types of activities.  Freshmen, on the other hand, are so thrilled NOT to be sitting still and listening that they will cooperate with virtually any alternative.


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