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Unplugging Plug and Chug


Yo - Memorize This!In a disturbing coincidence, the stomach-turning "Plug and Chug" phrase cropped up in 2 situations this week. In physics class on Wednesday, a student made a comment about "plugging and chugging" to get a solution. I stopped him at that point and did my typical rant against that type of approach to doing physics. (Note - he was NOT advocating it!)

In short, there’s nothing more revolting to me as a physics teacher, and a physicist than the thought that somehow physics can be taught, and learned, by memorizing formulas and simply plugging in numbers and calculating.

How then to explain a quote by Erika Gebel in the Aug, 3, 2007 Philadelphia Inquirer? In an article titled "Masters of ‘spring’ theory: Physics Teachers embrace a new method", Gebel is describing exciting new changes to the way that physics is taught in high school. Citing the approach known as modeling physics , which had just been taught to local physics instructors in a faculty-development workshop in the Philadelphia area, Gebel reports that

Modeling is a departure from the traditional method, often referred to in physics circles as "plug and chug." That is, solving problems by plugging numbers into memorized equations - F = ma, F = mg, F = kx, and so on - then chugging through the math. In traditional physics, students are expected to memorize the equations before they really understand their meaning - that force, for example, is equal to mass multiplied by acceleration.

Now I am all for the modeling approach. In fact I know the instructors quoted, have observed their teaching, and have observed their students really catching on to physics concepts at an amazing level. In short, modeling works when it is done well.

But I sincerely doubt that any physics instructor would make a comment such as given by Gebel. In all of my years in physics, with different instructors, many different schools, I have never heard anyone espouse this "plug and chug" approach. The line that really bothers me is that "students are expected to memorize the equations before they really understand their meaning." I have never seen a textbook that simply gives an equation to be memorized.

Now I can imagine a statement to the effect that students often understand the meaning of an equation only after solving a set of problems using the equation. But this is after the text and instructor have presented either a deductive argument, or plausible explanation (that includes experimental evidence) for the equation.

Claiming that instructors expect memorization before understanding does a great disservice to those physics instructors who have labored for years to make sure that understanding physics is the ultimate goal of teaching and learning in the physics classroom.

And I’m sure that all physics instructors - regardless of whether they teach modeling or a more traditional approach - are all too familiar with a sizeable number of students who actually would prefer the "p& c" approach. These students are the most challenging to teach, and when they finally realize that approaching physics by focusing on concepts and unifying principles, with the mathematics in a supporting role, well, this is the reason I love to teach introductory physics more than anything else.