# Day 71: Unbalanced Forces Practical, Mistakes Whiteboarding, & Density Practical

AP Physics 1: Unbalanced Forces Practical

Since tomorrow’s assessment will include a second shot at our unbalanced forces learning target, we did a practical where students used unbalanced forces and constant acceleration to predict the velocity of a cart after it traveled a certain distance down a ramp. While we haven’t really dug into energy calculations yet, I did encourage students to try doing it as an energy problem if they had time, and the groups that tried it were excited to see the same answer two different ways.

Physics: Mistakes Whiteboarding

Students did mistakes whiteboarding to go over yesterday’s problems; not surprisingly, it went very quickly. I also didn’t have to get on students’ case about units or well-labeled diagrams, since they are at a point where they find it useful to see and were asking each other for that information when someone left it off.

I noticed a couple of groups in one section had started some interesting notation for their unknown I haven’t seen before; students really, really like to use x for their unknown, which I push back on, but these groups were using x plus a unit for their unknown. I can’t quite decide whether I like it; using x as an unknown does get in the way of using x to represent position, so I know I’d rather they use the standard variable. On the other hand, seeing the units written out for the unknown helped a lot of students see what math they needed to do and the students I talked to were very clear that “x m/s” represented how many meters the object traveled for every second, which the students just using v were not as consistently clear about. I’m trying to decide whether the potential value here outweighs the hurdles it may cause down the line; one option is to let them leave the units, but push they should still use the standard variable (like “v m/s” here). I don’t see myself ever introducing this kind of notation, but I’m also not sure I need to get students away from it if they find it useful.

Chemistry Essentials: Density Practical

As a practical to wrap up the density unit, I asked students to plan an experiment they could use to answer either whether the shape of an object impacts its density or whether the volume of an object impacts its density. It went about as I expected; initially, students were uncomfortable with how open-ended the task was, but, once they got started, they moved forward easily with the task. I think the challenge had more to do with students’ discomfort with this kind of task than their ability to complete it.