# Days 82-86: Projectile Calculations & Momentum Conservation

AP Physics: Projectile Calculations

This week we worked on wrapping up projectile motion by focusing on calculations. Students were a little rusty on using velocity vs. time graphs to set up equations since we haven’t practiced it in a while, but I was very pleased with how quickly they got back into the groove with those skills. We ended the week with the classic projectile practical where students predict how far from the table a marble will land and it was great to not only see students nail it, but feel good about nailing it. Once students succeeded, I gave them a lighter marble and asked them to predict where it would land relative to their original, heavy marble, which lead to some great conversation.

Physics: Momentum Conservation

This week we started transitioning to quantitative momentum conservation, including a lab where students did a series of collisions and comparing the total momentum before and after the collision. It’s always tricky for students to make sense of the graphs produced by the photogates, so this year when we had some extra time the day before, I tried doing a few collisions and projecting the results. Then, I had students get into groups and whiteboard their interpretation of which velocity was which. That exercise paid off and the lab went the smoothest it ever has for me as students were much more confident at reading the graphs with the skill to back it up! We ended the week with Kelly O’Shea’s momentum card sort, and there was a really great moment where a student was explaining to me how he worked backwards to make a velocity vs. time graph from an equation by solving for the unknown velocity. Given how much I see students struggling with math reasoning, it was a lot of fun to see a student feeling confident enough to make sense of the equation in that way, which I don’t think would have happened if we’d gone straight to problems.