Day 91: T-10 Days Until Final Exams

Tuesday, Feb 13

Physics: Refraction lab! We got half-moon petrie dishes with some water in them, and lined up a pin on one side with the refracted ray of a pin on the other side. It was not easy for the students to figure out what to do, so I worked with each group individually to help them sort it out. There were lots of questions about how much data to take. I told them to take all the data they could. It’ll be interesting to see what patterns they find, especially with the bigger angles.


Some students were getting refraction angles bigger than incident angles, so we had the class-wide discussion about riding on roller skates from concrete onto grass to explain the direction change. I really do need to learn how to roller blade without killing myself or build some kind of demo that shows a two-wheeled object changing direction as it goes from tile to carpet. Maybe something along the lines of a roll-back can that has the winding mechanism in the axel and large wheels on each side. The ideas, I am having them.

Honors Physics: It’s time to plan the final exam! We did it together so that everyone knows exactly what will be on it. We’ll write the short answer questions on Thursday, and I’m to have a set of multiple choice questions for practice ready to go by Friday for them to do over the weekend.


We finished with the field inside a capacitor on Monday, so today was moving to potential energy in a capacitor and near a point charge. It took a while to sort out why negative charges have negative potential energy, but I think they’ve got it for now. We will definitely review tomorrow, but we absolutely need to talk about potential. I’m glad tomorrow is a 45 minute day, so I have a little more time, but I think I’m going to need to do a bit of straight lecture instead of an interactive lecture/discussion so I can teach the concept and then swap back to more student involvement once I’ve hit the high points.


AP Physics: I showed one class how capacitors work with my electric playground yesterday and the other class today. The second class asked me a few other questions, so I built another circuit to show them the switch from the LED being lit by the battery to it being lit by the capacitor as it fades, so I also showed that to the other class today.

For AP Practice, I gave them the practice test with magnetism and induction problems crossed out. There were a few people in the second class not engaging at all with the practice questions, so I sat down with them and talked them through the first few questions and asked them to find at least three questions they knew they could do in the packet as homework. The rest of the class seemed to be deep in discussions about the questions, so I let them at it.

In the first class, they were getting stuck, so I coached them to go through and get all the easy questions first, get the low hanging fruit, the cheap as free points, and then come back and stew over the others. Quite a few of them, if you have the conceptual understanding down, you can answer without doing any math. Do those first. Then do the ones that require math you know. Then do the ones you’re not quite sure what’s going on. Because sometimes, just sometimes, one of those you know how to do will trigger the knowledge you need for the one that confused you the first time around.

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