Day 108: ‘Breaking’ the Energy Transfer ModelPosted: April 10, 2014
I end the energy unit, and start the momentum unit, by asking students to analyze two carts crashing and sticking together with velcro. I ask them to predict the final velocity using energy transfer. The above board is where students hit the snag in trying to do so. We can’t measure changes in thermal energy easily!
What’s interesting is that when I did this last year most kids left out the change in E_therm. I know I did a MUCH better job the second time around in the modeling energy unit this year, and this is a sign of that. Today’s activity was much more interesting last year, however, because they all assumed no change in E_therm, so when they went to try it in the lab, they were surprised. This year I just asked groups when they got to the point above, “Can we measure changes in E_therm?” “Uh….no…” “Right, so let’s neglect it and see what happens.” Then their prediction doesn’t work out, BUT they see that the final velocities do have a pattern to them, which drives the development of the momentum transfer model. I wrote more about this process in this post.
Oh, also, I showed kids double LOL’s a while back, and a couple groups tried it on this scenario, which was really fun to converse about.