AP Physics: Force Vector Addition
Students worked some problems with balanced forces in two dimensions. We also had some discussion about whether you could have a mass hanging from a perfectly horizontal rope and used some hanging masses and string to experiment with some of the ideas. Not surprisingly, they really wanted it to work with a small enough mass in the center and a large enough force on either side, but once they started drawing free-body diagrams, it became very clear that the rope has to flex.
Physical Science: Magnets
Students played with some bar magnets and steel filings to start building some ideas about magnetic fields. Every year, my 9th graders struggle to see patterns in the filings, even when they are very clear to me. I usually have them start with the filings, then get out a compass to compare the patterns. Next year, I might have them plot the orientations of a compass arrow first, giving them some specific positions around the magnet to check, then get out the filings. That should give them an idea of what to look for in the filings.