OK, so we talked a little bit about angular momentum yesterday, and I didn't write about it. I walked past the rotating platform and dropped a book on it. We noticed that mechanical energy wasn't conserved, and we didn't have a good way to calculate the dissipated energy. We noticed that momentum wasn't being conserved, because the rotating platform didn't slide forward. But it did rotate, so something was being conserved. We decided it was angular momentum, and, by analogy, came up with a formula for angular momentum. We played with the bicycle wheel on the rotating platform, which we could explain with angular momentum, along with the classic ice skater spin.

Today, we whiteboarded some problems and then watched one of my favorite videos: Veritasium's bullet-block experiment. It is so motivating and a great way to make students apply energy, linear momentum, and angular momentum to a problem.