Today, make good use of time to hit energy topics. The big ideas include kinetic and potential energies, that relationship between force and potential energy, F = -dU/dx, which is used with potential wells, and work. Power is also fair game. There are videos for potential wells, gravitational energy, and springs (elastic energy). You will also get a review set. For the 3-4 class, keep in mind the addition of rotational kinetic energy for rotations.