As I mentioned yesterday, these past two days were an opportunity to pilot a portion of our units with the rest of the advanced workshop participants acting as students. Today was our day to present and we tested our practicum for the balanced torque model. If you’ve ever taught rotational motion, I’m sure you’re familiar with it.
This problem is in every physics textbook, so we decided to drag it kicking and screaming into the real world. Here is our take.
Starting with only the board, first, without showing the readings, ask students how the readings on the two scales will compare. (We used force plates and Logger Pro.) They guess that they’re equal. Awesome. Show them the readings. Ask them what the readings can tell them. They figure the weight of the board. Cool, then hide the readings and push scale #2 in towards the center of mass, maybe 1/3 of the way in. Then ask them to use the balanced torque model to predict what the two scales will read now. Let them work through it and bring you their prediction. Check against reality. Horray!
Now, we ramp up the challenge. Since every physicist loves symmetry, we want to keep the scales at their new locations, but get them to read the same thing again. So, we drug out a crate of books. The challenge was to decide where to place the crate of books on the board so that the scales read the same thing. Make what ever measurements you need to, feel free to move the board, but you have to place the crate on the board yourselves.
To say that the teachers in that room were engaged was an understatement. Not all of them had the background for this topic, some of them had it in the past but had forgotten it and some were well versed. We were lucky to have so many hard-working “students” in our class. Tyler and I circulated around the room, helping where needed, being less helpful when we could and looking for misconceptions that our students may have. Overall, awesome presentation. But in all honesty, I don’t care about how well it went for our sake, because here is what I want to share tonight. Here is the power of modeling instruction made manifest.
One of the teachers today came into the unit having studied rotation years ago in an intro physics class. Her knowledge of this topic had been long forgotten when we unveiled this problem today. I spent some time at her table, talking to her about the ties between balanced force and balanced torque. It was clear, she wanted to learn. Why? Her grade for the workshop (we can earn graduate credit) didn’t depend on this activity and all she had to do was provide us with anonymous feedback on which she could have written very little or even a message about how this was beyond her experience. In other words, she had no vested interest in this problem and could have easily given up. But she didn’t. She dug in, wrestled with the ideas, tried things, failed at them, and tried some other things. She dealt with her confusion and frustration head-on and then, just as we were wrapping up, brought me an answer and excitedly asked if it was right. We uncovered the scale readings and she was spot on. And then, this adult woman, who had just spent 30 minutes working to learn something for no other reason than to know it, burst into dance. The joy she felt at having learned simply could not be contained. I wish her students could have seen her today.
Dammit! Do you people get this?! If this was a problem in the book for homework, do you think she’d have that reaction? She said later that she probably would have given up frustrated if it were. I bet your students do that and then come in the next day and ask you to go over the homework. Anyone reading this probably does get it since you’re interested in modeling instruction. But to you then, I have to ask, how do we get more people to see the power of this? How do we get them to realize that we can make our classrooms – any classroom – about learning and not about grades?