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Yes. It's true. I try to remain calm, but inside I am terrified.
Here is the situation. The class is a physics for education majors using the awesome Physics and Everyday Thinking curriculum. At this point in the class, the students are wrapping up their discussion of forces and motion. They have collected the following evidence:
- When you push on something, its speed changes. This is limited to motion in 1-D.
- When you stop pushing on something, there is no longer a force from that initial push.
- Things slow down because of friction and friction is a force acting on the object in the opposite direction to its motion (again, limited cases here).
- For an object with balanced forces, it will either be at rest or move at a constant speed.
- For an object with unbalanced forces, it will speed up if the greater force is in the direction of motion. It will slow down if the greater force is in the opposite direction as the motion.
For this particular part of the activity, students are having a discussion about three example explanations that they are trying to evaluate. The explanations are trying to show why an object with no friction (or negligible friction) would move at a constant speed after being pushed. One explanation is essentially correct (B). The other two have problems. The first one has balanced forces after the object was hit - the force from the hit and from friction (explanation A). The last one has no friction and just the force from the thing that hit it.
I am not going to show your the students' discussion. Instead, I will show you what I am thinking about during the discussion.
Ok. Let's get this thing started.
Some students like the first explanation. Really, I am not surprised. Someone will point out that it is wrong, won't they?
It seems most of the students are going with the "balanced forces" argument. Don't they remember their evidence that says for is not transferred?
Well, maybe they will all like the next explanation. What?? They think it is poor because it doesn't say anything about the hand that pushed it. Oh dear. This is not going well.
Wait. That student just clearly explained why the second explanation is correct. Why don't all the students agree? This is bad. I think most of the students still like the first explanation. Maybe I should stop them.
I won't stop them. I will cheat. Let me ask the student what she was really saying. Yes, I will change a couple of the words to make it clearer. Is this what you said (or meant)?
That didn't work nearly as well as I thought. I failed. They are going to fail. Either I will have to tell them that is wrong or just let them go on being wrong. Argh! Maybe I will move to the other side of the room. Will that make a difference?
Let me give them a pause to think. I will use my standard 10 seconds at least (they can rarely make it past 10 seconds of silence). It worked! They started talking again.
Yes! Yes! They figured it out. Make sure I am sitting still. No jumping. No yelling. Just sit there looking like you are thinking. Try thinking about something else. Think sad thoughts. Think about that dumb committee meeting. Oh, that works. I think they bought it. They aren't looking to me for approval. It was close though.
Update
I really should have included this picture. This is what I keep in my mind while they are discussing. Don't let your expressions give away the answer. This is Dan Meyer (dy/dan) from one of his – video presentations on "Be Less Helpful"
