Day 18 & 19: Under Pressure

Monday, Sept 24 and Tuesday, Sept 25

Physics: Monday Exam! Tuesday Lab 2! It’s a modified Atwood lab where a cart is accelerated by a weight over a pulley. Students will be measuring the acceleration from the experiment and predicting it from Newton’s Second Law, and the goal is for them to recognize that the difference exists because you can’t assume friction is zero.

Honors Physics: Monday I answered lots of questions that came up in the Friday 3-2-1. There was confusion about some topics, questions about some class procedures (I hadn’t made certain decisions yet, so didn’t have an answer until now), some inquiries into why I hadn’t graded something (I messed up is the reason :I ), and suggestions for improvement. There wasn’t time to get to everything on Monday, so Tuesday was a continuation of the questions and suggestions and finally beginning the Ideal Gas Law in a formal way.

Quite frankly, I’m starting to get overwhelmed. I’ve gotten behind in everything, and every time I catch up I blink and am behind again. Yes, I know this job is relentless; I’m not complaining about the job. I’m complaining about my ability to suck it up and DO THINGS even when it’s hard. I love this job and my students and my subject and my life so, so much, and I’m so worried that I’m going to lose it all, but apparently that’s not enough to make my brain behave. Brains are jerks.

Bonus: I got to tell the Newton-Pascal Hide-and-Seek joke in both Honors AND Regular today. BOOM!

pascal_1_newton_per_square_meter

AP Physics: Monday we began system schema and free body diagrams. I used a modified version of Kelly’s “Building the Balanced Forces Particle Model” to introduce the things, but at the AP level and without room to sit in a circle and play with the toy. Damn my tables for being bolted down! Tuesday we looked at our first AP Free Response problem. I gave them one from AP B since AP C questions don’t have much in the way of kinematics-exclusive FR the way B does, and it’s easy enough for them to see how the things we’ve discussed in class are useful on the AP. Since I’ve got one class for twice the time of the other today and swapped on Friday, I’m going to have to do a little bit of interesting scheduling, but it should all work out.

What we did in that extra time was begin looking more deeply at N2L systems. I came up with four categories of N2L problems based on all the problems I could think of: stacks, pulleys, connected by ropes, and inclined planes. Most problems seem to be some combination of those things, although I may end up broadening if I come up with more archetypes. The second one under inclined planes was my weirdo combination of all four to show them a possibility.

N2L.jpg

My goal here is to help them identify N2L problems on sight and be able to identify the first principle required. Knowing the novice/expert split in categorizing, I’m looking to front-load recognition. When we get to energy I’ll figure out how to help them distinguish between conservation on a slope and N2L on a slope. I’m having a hard enough time keeping up to be looking that far ahead right now.

 

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