# Day 33: Collisions and Machines

Thursday, Oct 19

Physics: We talked about energy and how most energy on the Earth, including fossil fuels, originally came from the Sun. We also reviewed the pulley lab from yesterday where we put up the data from all groups and looked for the patterns in the data. It’s not the hardest pattern to find, so they were quickly able to discover that the more pulleys you used the greater your mechanical advantage. I was hoping to also see a pattern in efficiencies, but that was all over the place so I couldn’t draw a conclusion or help them see one, so we focused on the patterns we could see. I want to do this whole lab carefully and see if there is a pattern in efficiencies, because my gut says there should be, but it also depends on the quality of the pulleys (not great) and the reliability of the scales (even less great), so with this equipment I doubt anything consistent can be determined.

Honors Physics: Looked at forces and the pendulum, drew some system schema, discovered that one FBD doesn’t cover the whole story, decided where we could draw a FBD that made since, and applied N2L. Talked about how forces that are perpendicular to an object’s motion are different from forces that are parallel to an object’s motion. Thought our way through how the force necessary to turn an object is related to velocity, mass, and radius of curvature. The goal here is to show students how a pendulum starts to bring together all of the ideas that we have talked about so far into one package, and has even more exciting things to discover and learn about.

AP Physics: Because of our rather garbage equipment, I decided to go with the PhET collision simulation and use some of the provided materials and then augment them to include 2D collisions as well. When we tried the collision activity in the regular class, the data was hilariously bad, the photogates were finicky (they still use visible light. Like, a flashlight of visible light, not a red laser or anything), and the results were not at all helpful to understanding the idea of momentum in collisions, so at least the PhET sim should have consistent and repeatable results. Or, at least, it does for the 1D collisions. The 2D collisions, especially with 3+ objects, can be slightly less consistent, but it still does a great job and has plenty of potential for fooling around and playing.