Day 14: Two Awesome MistakesPosted: September 17, 2013
First hour today I had students start to whiteboard problem 1 from CVPM practice 3, and I immediately realized that they didn’t understand what the physical situation looked like. As a result we paused and I had every group sketch a physical diagram of the situation. Every group, with about a 50/50 split, drew one of the two shown above. The difference between the two (and the non-purposeful ambiguity of the problem itself, which I may actually leave in for next year) lead to a great discussion about how it should look. It also led to great discussion about the location of the origin (asterisked on the right board) and the direction of positive. Note that the group on the left actually labeled the origin as the entire line from A to B. I believe that they were confusing the diagram with the position vs. time graph, in that we had had a conversation about how the horizontal axis is the location of the origin on that graph, they tried to generalize it to the diagram as well.
Because of all of this I added a question for next year to first have the students diagram the situation. After the experience first hour, I had both 2nd and 3rd diagram it first before we even looked at the rest of the problem. Now that I think of it, I probably should have just had them motion map it…thoughts?