Day 9: Forces at Angles and Interaction Diagrams

Today was all about how to deal with forces at angles. I had them, for the most part, come up with numerical ways to deal with components and vector addition diagrams, and then I summarized their methods in a chart. Then we tried some problems in class. I modified some classic Modeling Instruction questions to be only in variables to get them ready for what they'll see on the AP exam.

Day 8: Forces at Angles

Today was all about forces at angles. We worked on two problems. The first was on a force table. One force was at 0°; the other at 90°. Students knew what the picture should look like, but they figured out how to do the math in their groups without me teaching it. The last picture is their homework assignment. What can they figure out about this situation?

Day 7: Forces at Angles and Trying to Quantify Forces

We had a long discussion about how to analyze forces at angles. When a person pushes a table at an angle, should we call that a normal force? A normal and a friction force? We decided that perhaps an applied force would be a way to sidestep this debate. We also debated which direction friction point. This even required, after I thought the discussion was done, a student call up another student to go through question 2 (pictured) after I thought we came to a class consensus. Hey, if I'm wrong, feel free to call someone else up!

Then I introduced two ways we can look at forces at angles--as components and through vector addition diagrams. I lamented we had a no way to quantify forces. So it was off to lab to figure out some quantitative relationship involving the force of gravity. We were creative about what objects we used as test masses.

Day 6: The Mistake Game

After they took their test, we did our first mistake game (Thanks, Kelly O'Shea! Your blog is great!) on the whiteboards. For most of the questions, only one of the students was supposed to make a mistake. On the last question, I told all the students to make a mistake. We had the best discussion when everyone made a mistake.

Day 5: Starting BFPM

We started today by trying to figure out when constant velocity happens in the real world. We weren't sure, as a class, if we had two fans of unequal strength, if the cart sped up to a certain constant speed or was always speeding up. We had to take the cart off the track and put it on the floor to check.

Then I talked about the four major types of interactions (gravity, normal, friction, and tension) and about how to make an interaction diagram. Then we practiced making interaction diagrams and free-body diagrams.

My students don't know yet how important interaction diagrams are. Wait until they see how we use them in MTM and ETM.

Day 4: Finishing CVPM and Talking about the Grading System

We finished CVPM today. We had two really good discussions. One was centered on the question "Should the last dot on a motion map have a velocity arrow attached to it?" The other centered on the question "If two objects' position-time graphs cross, are they moving at the same speed?" We also carefully distinguished distance and displacement for the first time, and related them to speed and velocity.

More importantly, I introduced my grading system. I had a simple Red-Yellow-Green Standards-Based Grading system last year, but I think, just due to who I am as a grader, that my Yellow band was way too wide. I split Yellow into two different levels: Proficient and Approaching. I think this will help students know whether they are just making a few mistakes (Proficient) or whether they need to spend some time working on their conceptual understanding (Approaching).

Day 3: Multiple Representations of CVPM

We used the motion detectors today to experiment with translating between motion diagrams, words, position-time graphs, and velocity-time graphs. We also learned how to calculate velocities from position-time graphs and change in positions from velocity-time graphs. And, by the end of Day 4, we'll be done with CVPM.

Day 2: Pre-Testing and Refining

We took a pre-test, went over the (mostly mathematical) summer work, and finished up writing our Constant Velocity Particle Model. We went over the four ways to represent CVPM; motion diagrams, algebraically, with words, and with graphs. I also showed my class this blog. This way at least I'll have a few students in my audience, and maybe they will remind me to take pictures. I took no pictures today. 

Day 1: Buggy Lab

After the bare minimum of formalities (fees, fire exits, safety form), we started the buggy lab. We made the claim that "the buggy travels at a constant speed." We then went into lab to collect evidence.  After whiteboarding our first attempt of displaying our evidence, we came up with a class consensus of what makes good whiteboard evidence. Here's the best second draft of their evidence. (We'll be working on the equation more tomorrow.):

Day 0: Random Conversations

Today was the day before school started. After a morning of professional development about differentiated instruction, I went to my room to get ready. Instead, I wandered around, helping people with computer problems, asking for help setting up my room, helping a teacher set up WebAssign, asking for help about a few students newly added to my classes, and helping a teacher get his head around Modeling Instruction. I love these chance conversations.

Tomorrow, I'll be trapped in my room, and I'll start taking pictures.