Physics 11 – Today the students had their first constant acceleration “equation” quiz. I tried to incorporate some smart questions into it. The first question is “low floor”. Everyone should have success with it. The second question is a boilerplate physics 11 question that the students are expected to be proficient at. The third question is designed to reveal a common mistake. Students will be tempted to use the d=1/2(vi + vf)t equation, using vo = 0. This turns a constant velocity question into one that (mistakenly) has acceleration. We went over the quiz and several students made this mistake. I wonder if hammering on this mistake will prevent it from happening… No, it won’t be it will hopefully reduce its frequency.
Physics 11 – There was about 15 minutes of direct instruction in today’s lab. I wanted students to learn about tangent lines, so I worked through a set of arguments that would communicate how a tangent line on a position-time graph is the instantaneous velocity at that point.
So some kids get this pretty quick. A lot of students, when asked to draw tangent lines on their position-time graphs, start drawing lines between two points. I really have no explanation for this. While I can understand a student having a fuzzy idea of what a tangent line represents, it’s difficult to say why they would read the above and draw a line that crosses their curve in two points.
Physics 11 – Students continued to work on their constant acceleration lab, creating the position – time graph, and then using it to get velocity information. I think there are some problems with this lab, where the students have to be told how to use the x-t graph to get velocity. They get the idea but it involves a bit of hand waving.