**AP Physics: Impulse**

Students did a lab I saw at a Modeling Instruction workshop over the summer. They connected a cart to a force sensor with an elastic string, and used motion detectors to produce velocity vs. time graphs. They collected data to make a graph comparing the area of the force vs. time graph to the change in velocity over the same time period. Introducing the lab felt pretty hand-wavy, so I need to think about how to do a better job of motivating the lab, but the data tables are looking good.

**Physics: Big Pendulum**

My big goal today was to motivate relationships besides linear. Since the data collected in the classroom for the pendulum lab tends to look pretty linear, I had students predict the period for a pendulum about 5 m long, then we went to a spot in the school where we could test it out. Since the period was shorter than expected, we started looking for other flaws in the linear fit, which lead to some good discussion on the intercepts of the linear graphs before we took a look at some other relationships and learned how to linearize.

**Chemistry Essentials: Alka Seltzer**

Today, I replaced beakers with plastic cups and we looked at the change in mass of Alka Seltzer in water before sketching some particle diagrams. Every group connected the fizzing in the water to the loss of mass, which lead nicely into the idea that gas has mass. There was some great discussion afterward; students were not only eager to ask interesting questions like what would happen if we had a way to trap the gas, they were also excited to share their ideas about what should happen and why. I usually start the second half of this course with a chemical reaction in a plastic bag to show conservation of mass, but I’m thinking about moving it up since it addresses questions that students are excited and curious about right now.

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