Is Modeling Instruction Working?
My classes just finished doing a conservation of momentum lab. In many ways it was a big disappointment. We ended up spending 2-1/2 classes on the lab, with little to show for it. The general idea was to record position and time data from 6 videos (6 different types of collisions), calculate velocities and momentum, and compare total momentum before and after. There were lots of problems with this:
Students would make mistakes in recording data or making a calculation, and every mistake helps to obscure the goal of seeing that total momentum doesn’t change.