Floor vs. Table

IMG_20130212_090108100 I used to have students put their whiteboards on top of the lab tables, leaning against the support rods. Now I have them place the whiteboards on the floor, leaning on a stool. I like this better, because students can’t “hide” behind the board. Here the AP class is going over some electric field problems.

 

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Applying the Model

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67 With some effort, students got through a couple of problems from one of Kelly O’Shea’s packets. There is still a lot of confusion on units, but I am trying to blast through the rest of CAPM this week and planning to start unbalanced forces after break. Wish me luck!

(The rectangular area is obviously not 91 m, but the girl who wrote 16 was on the opposite side of the board from the girl who was writing most of the work. Similarly, the triangular area is not infinity, but 8 m.)

##CAPM

 

Fun Problems!

20121205-160322.jpg59 I LOVE these types of problems. We have finally made the transition from massless pulleys to pulleys with rotational inertia. Now we are revisiting Atwood-type problems with this added twist. I could sit and solve these things just to relax. This is the AP class.

Two for the price of one



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I could not decide which class I wanted to talk about, so you get two photos today. The top one is from one of my conceptual classes, a great example of a mistake in which students assume that there must be some sort of straight upward force to balance the gravity force. This is the way all the FBD’s we made at first were laid out. In this problem, there should not be any surface force at all, which the system schema clearly shows. So we discussed that in class. I also spent time talking about how important this mistake was for everyone’s learning and in a later class I asked a group to add this particular mistake to their FBD, which they found distasteful but they did it anyway.

The second photo represents the successful use of Tracker to analyze a rotational motion video. I have a collection of 8 videos which I made several years ago and students have always done the analysis in Logger Pro, clicking through hundreds of frames. Ugh! Happily, last summer I learned how to use Tracker and all the groups were able to have Tracker autotrack a spot on the cardboard “record,” a process which wound up being painful in much different ways. I could go on and on about the technical issues we had but happily most of my students are resourceful and some are handy with tech support, so every group now has data to analyze. We’ll be doing that tomorrow.

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Representations

36 The conceptual classes are slowly working through a version of Kelly O’Shea’s packet for Balanced Forces. They were doing a decent job of the system schema diagrams and FBDs. Students were working on this in class in small groups, and each group made a whiteboard of the same material, and we compared them and looked for differences. We then discussed whether those differences were acceptable or if they made the solution incorrect.

##BFPM  ##FBD

 

 

 

Time

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14 Apparently this group of AP students found their assigned problem too easy. While they were waiting for the other groups to finish, they decorated their board. No, I don’t know what a Dido is. I thought they were headstones for graves.