# Day 10: Bowling Balls and Balanced Forces

New packet day! My friend and fellow physics teacher Leah was visiting today* (and gets all of the photo credits here). We immediately went out into the hallway and started playing with the bowling balls. The first two questions have pretty obvious answers (How do you speed up a bowling ball using taps? How do you slow down a bowling ball using taps?).

The next question (How do you keep a moving bowling ball going at a constant velocity?) isn’t quite as obvious. We spent most of our class time there, moving about half of the speed through this discussion as last trimester’s class. At the same time, we put more thought into how to make observations, what our observations mean, etc than the last class did. Hopefully that will pay off as we keep moving forward in our forces unit. The hangups were mainly centered around the fact that, even though all of our observations pointed to the idea that a rolling bowling ball in the hallway had a constant speed, some of us really believed that it had to be slowing down. Possibly because of gravity. Or just because objects always do that.

We ended in the classroom working on a rule for tapping and speed. We didn’t quite get to share, but one group’s rule was something like, “If you want to change the velocity, it takes but a single tap.” And if you don’t want the velocity to change? “Leave it alone!”

Next class, I think we will start by looking at the hover disc for a few minutes (and thinking about the parallels/differences with the bowling ball), then use that same fan cart sequence. And someone’s getting a law named after them. The hunt is on!

* Having Leah visiting was so great! Just having another person in the classroom who is very familiar with what you are trying to do (and who is not evaluating you) is wonderful. Hearing what she saw me doing and being able to compare that to what I thought I was trying to do was really helpful. And she pointed out an idea that a student might have had (in my 9th grade class studying energy) that helped me recognize and talk about that idea with a different student in my other section the next day. Thanks, Leah!