The wrong kind of question

Following on from yesterday’s discussion of the paper by Gire et al. I’ll remark on one little aspect of this study that physics teachers and lecturers need to take note of. (Well, in my opinion they do, and I’ve got a steadily increasing pile of literature to back me up on this).

One of the questions that was asked of the students was "When I solve a physics problem, I locate an equation that uses the variables given in the problem and plug in the values".  Now, I would say that is not a good approach. No no NO NO NO! That approach yields no understanding to the student about what is going on.  But in the sample group, about 70% of first year physics majors, 80% of second year physics majors, and 90% of first year engineering students agreed with that statement.  The authors describe this worrying result nicely:

The unfavourable responses of year 1 and 2 students are striking because it suggests that students in the first two years of undergraduate study find the plug-and-chug stategy to be productive in solving physics problems

What this tells me is that we (that is, the teachers) are setting the wrong kind of problem, even in second year physics.  (By year 4 only 40% of the students agreed, and there is some comfort to be had that 0% of graduate students thought this approach was the one to take. The message that physics is not about sticking numbers into formulae gets across in the end, but it takes a long time)

When I set assignment and exam problems, I try to do so in a way that assesses the students’ knowledge of the underlying concepts, not their ability to choose and manipulate an equation.  But setting this kind of plug-it-in problem is pretty ingrained – for example it permeates many university physics textbooks, and it is hard to prise myself out of that mode of operation. If we ask questions that lend themselves to the ‘plug-and-chug’ or ‘stuffing numbers into formulae’ approach, we only have ourselves to blame when our students hit third year without understanding  the physics concepts that we thought we taught them.

Incidentally, the NZQA scholarship physics exam is a great example of setting questions that probe a student’s understanding of physics, rather than their ability to pick equations of a rack. If you are thinking about doing this exam – and agree with the statement "When I solve a physics problem, I locate an equation that uses the variables given in the problem and plug in the values" you will be in for a very big shock. 


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