There is a clear difference between naming and understanding and I see it in class every day. Inertia, for example, is a problem for physics students.
Following Aristotle from 350 BC and rejecting Galileo's "modern" science discovery 400 years past, my students consistently believe that in order to keep moving at a constant velocity there must be a larger forward force than backward force. This actually results in a forward net force that will increase speed. They're wrong. I've tried multiple choice and free body diagrams and fill in the blank; verbal and written formats - They're consistently wrong.
But they can fill in the blanks for "An object at rest ... and an object in motion ... unless ...." (will stay at rest ... will continue moving ... acted on by a force). So they can recite the basic Law of Inertia with a tiny bit of prompting but they have no idea that
"Inertia" is our NAME for a property of matter. It is NOT a force. It really isn't a thing. Inertia is a name for the natural tendency all objects have to resist changes in velocity. It is a measure of resistance to acceleration. It is measured by measuring mass.
And this is where I have to be careful. If I allow the term "inertia" to be used, they rename the net forward force they feel is necessary as "inertia." Then the following conversation happens:
Q: What causes an object to keep on moving?
A: Inertia. (Wrong. Proper answer - "It just does, nothing causes it")
Q: What force is necessary to keep an object moving?
A: Inertia. (Nope. Proper answer - "No force is necessary")
Q: Why does an object keep moving?
A: Inertia. (Sorry. Proper answer - "Nothing. It just does")
By naming inertia too early in the discussion, a student never has to struggle with the concept. By asking easy questions and accepting comfortable answers we teachers contribute to our students' lack of understanding. I do so on a regular basis.
In electrostatics, induction and polarization are often confounded. So this year I decided not to name them. Nor will I allow the students to name the processes in our discussions. They will focus on what the electrons are doing in conductors and insulators and that will suffice. I'll tell you how it goes.
No comments:
Post a Comment