AP Physics: Motion Detectors

This concept development sequence comes from conversations with Michael Lerner, Kelly O’Shea, and the rest of the Physics! PLC!

One of the tasks I gave students yesterday was to sketch a momentum vs. time graph for getting a bowling ball moving, then reversing its direction. There was a lot of disagreement about what that graph should look like, so today we had some brief discussion about how the momentum vs. time graph should compare to the velocity vs. time graph, then got out motion detectors and billiard balls to try some of yesterday’s tasks. The discussion afterward lead very nicely into the significance of a negative momentum, as well as the meaning of the slope on a momentum vs. time graph.

Physics: Board Meeting

We had a board meeting for the dowel lab, following Casey Rutherford’s Observations, Claims, Evidence structure. Even though all of the dowels were made of the same material, slopes were all over the place, so we had some discussion about how to improve the results next time. A lot of groups just wrote down their calculated volume, rather than the values they measured, which made it difficult to check their calculations, so we discussed the value in recording the measured values.

Chem Essentials: Burning

We continued the mass and change experiments, which today included burning steel wool. I needed to do a better job of framing this lab as being about the mass of the steel wool. A lot of groups missed recording the initial mass before they lit the wool, which I could have addressed by checking they had that value before giving them any matches. I also saw a lot of groups blowing on their wool or tossing used matches onto the dish with their wool, which reinforces that they were not thinking about the mass as important here.

AP Physics: p vs. t Graphs

This concept development sequence comes from conversations with Michael Lerner, Kelly O’Shea, and the rest of the Physics! PLC!

There was still some debate from yesterday about whether the bowling ball had a constant speed after a tap, so I pulled out the Motion Shot app to make a motion map. Afterwards, students did a variation on the bowling ball lab with combinations of taps to introduce momentum vs. time graphs. I picked a few scenarios to help them get the idea of negative values for force and momentum as well as some to get at the significance of a non-zero intercept on the graph.

Physics: Graphing

Students worked on their graph for the dowel lab, then we talked about “translating” the equation for the line of best fit by adding units and variables appropriate to the quantities they graphed. Students seemed to do well wrapping their heads around that step. Tomorrow, I’m going to have them write the slope as a statement a la Arons.

I’m also thinking about repeating the data collection tomorrow. Students are getting a wide range of slopes and intercepts and, if we’re going to take the time for a unit on experimental design and graphing, I’d like to establish careful practices right off the bat.

Next year, it could be interesting to mess with the calibration of the triple beam balances to give a non-zero intercept. I’m not sure yet if I would do that immediately, or if I would do a second round of data collection with the balances off.

Chemistry Essentials: CER

I put a CER at the end of yesterday’s lab, and students seemed pretty thrown by the reasoning piece. Today, I played the “My Dad’s an Alien” commercial and had students identify the kid’s claim and some of her evidence. Then, students got into their groups and had to fill in the reasoning for at least one piece of evidence. A lot of groups looked at why she might see something as evidence (like why the car seems like a spaceship), as well as why the evidence might support the claim. Yesterday, I felt like I was struggling to keep students on track, but today they were very engaged and even enthusiastic about the task. I think today I was much clearer about what they should be doing and what that looks like.