Day 4: Free Body Diagrams

Today we finished developing Newton’s First Law in two more classes. We got into some discussions about the nature of the upward force on the Hover Disc was when it was on. In some classes they wanted to call it normal force from the air (since we had slid paper under the Hover Disc and determined that it was not touching the floor) and in other classes we called it a “air force” since it seemed to them to be a very different type of situation than the “crunching” of atoms we call “normal force” when two solid objects interact.

4 Free Body Diagrams

My senior physics class was only half full today because some of the seniors had joined the freshmen on their retreat, so rather than finish up the sequence to develop Newton’s First Law, the ones who were there practiced drawing free body diagrams. They quickly got to situations where some of the forces were diagonal and it became clear that we were going to have to come up with a more robust way of determining whether the forces on an object are balanced or not. Vector Addition Diagrams here we come!

So far, starting with forces seems to have been a good idea. It’s exciting to develop a really important idea during the first week of school, and the Hover Disc activity was great at getting everyone involved. BFPM is less math-heavy at the beginning than CVPM, so we’re not using any prerequisite knowledge, which is great for student morale. Since basically everything they need to know about forces has been recorded on the front of their packet, all they need is a bit of prompting to look up details of each force and draw correct free body diagrams. Perhaps because of, in the classes where we’ve started practicing free body diagrams, many seem to be feeling quite confident about their ability to draw accurate free body diagrams for most of the examples.


The freshmen are on a retreat today and tomorrow, so I’ll continue reporting on Algebra on Monday.


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