We went over our applications of our model of friction, which really went better than I expected. Then it was time to introduce a new force, the force of friction.
But it isn't really the time. Usually, I move from unbalanced forces to projectile motion. I had all those packets ready. But, somehow, I thought it was time to talk about the spring force.
It wasn't what I planned, but it seemed to make sense. There's no reason we can't go back to projectiles when we know more about other tools to look at motion and force. And it was a great lab for where we are in our lab experience; I could let the students loose to use all the different tools at our disposal. (They all tried such different ways to do the lab; you can see that in the pictures.) It actually might be better to do projectile motion later, when we haven't just been focusing on kinematics for so long. It'll be a good way to reinforce and spiral back.
Or at least I hope. My subconscious made that decision, and now I'm going to try it.