Day 120 – DMV Conservation of Momentum


Physics 11 – Students used a variety of impulse/collision Direct Measurement Videos today. The goal was to collect data and analyze the total momentum of the objects in the video (system).

A couple of groups got a bit confused because there was missing information on the videos (these videos work towards using conservation of momentum to solve for unknowns). I may need to re-jig how I delegate videos to the groups next year.

Overall the DMV are a quasi-reasonable substitution for not having appropriate lab equipment.

Day 64 – Last Day of Lab




Physics 11 – It was a long road, but today the students finally finished their unbalanced forces lab analysis.  This took a lot more time than I had expected, and I would say that the work ethic has been pretty good.  Lots of kids were getting a bit mixed up with their data and calculations, so there were several times where I would grab their data tables and quickly calculate acceleration and graph in Excel. I had thought about showing kids how to use Excel, Desmos or Plotly, but opted to stick with pencil and paper.  Learning to use this kind of software would take another day of time. Heck, I even find Plotly and Desmos confusing at times.

I’m really wondering if it is worth all of this time to do a lab on unbalanced forces….

Day 61 – Direct Measurement Videos


Physics 11 – In preparation for the paradigm lab for unbalanced forces, today’s physics classes used Direct Measurement Videos (DMV) to analyze constant acceleration motion of a toy car.

The DMV we used were from Peter Bohacek at Carleton.  They are, simply put, brilliant.  Peter started making these videos a few years ago and in their most basic form, DMV are quite simple.  You shoot some video of an object moving and make sure there is some type of ruler in the scene.  Better videos will be shot at higher frame rates with better lighting, better apparatus and setups with very little lens distortion or perspective.  Once you have a video, you can analyze time (counting frames) and position.

Peter’s newest videos are put into an html5 video player with many more features.  For today’s class the DMV player we used allowed the user to pick different toy cars to analyze.

It took the whole class for students to get used to the software and gather data for analysis.  They were asked to find the acceleration of the toy car, but lots of students started collecting massive amounts of data and plotted position vs time graphs.  This was after we had a class discussion on how acceleration can be calculated directly from d = vot + 1/2at^2, or a = dv/dt, once you find the beginning and final velocity.  I’m not sure I’ll ever quite understand how students get off track so often (well, I think I know why, I just don’t know if I’ll ever get good enough to mostly eliminate it).