Last week a couple of my students were dressed up for something, and I remarked how good they looked and that we should do a Phormal Physics Phryday; they latched on to it. I also mentioned it to my colleague Ben, whom I work closely with, and many of his kids did it as well. Above is the collection of students we could get together after school, and below is most of my 3rd period class, the originators of the idea.
Today we started unbalanced forces by brainstorming situations where we could explore how unbalanced forces operate in the lab. On kid actually described an Atwood Machine perfectly without using the name, so I drew it and commented on how it is a famous physics apparatus. We will be pulling something with a spring, thought I am fine with groups choosing other options as well if they want. This particular lab, as a paradigm for UBFPM, I want to keep them uniform. We’ll be doing some more open lab design to investigate friction later.
Recently I find that every time I say something like “the best way to approach this problem is…”, kids find a clever, elegant, or just different way to approach it. The force addition diagrams above are a great example.
The kids had some pretty awesome problem solving going on today.
I’ve probably written about this before, but Kelly sold me on force addition diagrams last year and I don’t think I’ll ever look back. So far I haven’t come across a situation that I’d rather use components on. This was from the problem below, we spent a whole hour on it. At this point this group was still wrestling with how to use the FAD to solve the problem.
This graph is created from the setup shown below, a modified Atwood machine, showing that the tension in the rope decreases when the system starts to accelerate. I’m going to spend a day having students predict, then whiteboard with diagrams, then replicate the situation with data.
My students are struggling on the difference between equal and balanced. This is what I wrote on the board, but not sure I like it. Thoughts?
Today I led the classes in a series of Newton’s 3rd Law demonstrations. We learned the above demonstration from Eric Gettrust, our Modeling Instruction leader, which he published in The Physics Teacher. The purpose of this demo is to model the interaction between a person and the Earth, showing that the attraction force itself is equal though there is a greater effect on the smaller object. Close up below.
I also do car crashes (picture below), tug of war with two force detectors, and the class favorite, chest bumps with force plates.
I finished the UBFPM packet today, but I won’t be printing for a couple days yet. The packet is here, and you have comment rights. Have at it, I’m always loving feedback. Or comment here. Or on Twitter.
Addendum: I forgot to mention that I once again borrowed heavily from Kelly.
We have done very little problem solving with BFPM, so naturally I left my students to work on it themselves. I had an all-day meeting for science articulation, and the directions I left were for each group to whiteboard problem 2, circle up, debate and choose a best answer, take a picture and send it to me. Then repeat with problem 2. I can’t wait to check in with them tomorrow about how it went, specifically discussing 3b. Other classes below. Oh yeah, the problems are from Practice 3 here.