[Sorry for the brain dumps, but…]

Day 2: Energy and Frequency Relations in SHM

1. Clicker Question Review of SHM Graphs: Day 2 started with a review of what was learned in Day 1. We quickly ran through two clicker questions that showed a position vs time graph for a horizontally oscillating object and students had to identify the sign of the net force and velocity at different points along the graph. In discussing where velocity  = 0, we had two nice ways of talking about this-one being that at a turn around v= 0 (e.g., like free fall), and two that the slope of the graph was zero. Similarly, in a location with negative velocity, we could describe particle as moving from right to left or point to slope as being negative. Students had a harder time (at first) identifying the sign of Force correctly from the graph.
2. Direction Instruction with PhET Energy Skate Park: I pulled up PhET simulation “Energy Skate Park” that begins with the skater in the bowl. I had previously set y=0 to be the bottom of the bowl (so that E = Kmax= Umax). I quickly oriented students to the simulation as an example of an oscillation that at least approximates SHM.
• Then I posed the question, “On this skater’s path, could you point to a location where the skater has maximum kinetic energy? Where could you point for maximum potential energy? Where could you point where the skater has both kinetic and potential?” As usual I emphasized that students should explain how they know / can tell. Students in pairs discussed for a bit. In bringing it back to discussion, I reminded them of the terminology “energy transformation” and the importance of choosing a system to do energy analysis. Since I was projecting the simulation on the whiteboard (not screen), I also marked various locations with “Umax”, “Kmax”, and “U+K” on top of the simulation
• The next thing I brought up was the Energy vs. Position graph on the PhET simulation. I oriented students to what the axes were plotting, but didn’t explain anything about the graph. I asked them to turn to their partner and “see if they could make sense of what this graph was showing about the energy, and see if they could explain it in a way that an smart 8th grader would understand”. In circulating, there was a lot of peer teaching going on. Back in whole class discussion, my job was to emphasize a few key ideas, using graph as away to anchor it. Total Energy is a constant; and at the extremes, the Total Energy was all Potential (E = U max); and at the equilibrium position, the total energy was all kinetic (E = Kmax). Anywhere, in between the energy E = K + U.
• The last thing I did was connect the discussion to the reading and in doing so quickly formalizing some of this to quantitative relationships in the text.