Tracker for Video Analysis

I've blogged about Tracker before, but I have to say yet again that it totally rocks. I have this video clip that I use with my students every year of a student jumping as high as he can. Joe, the student, does the predictable, he lifts his legs and arms while in the air.

Traditionally I've had students track the motion of three points on Joe. His head, torso, and feet. We've already talked about the acceleration due to gravity near Earth's surface so I ask them why the acceleration of the different body parts is not -9.8 m/s/s. I also make them explain why Joe's torso is closest to -9.8.

Well Tracker allows us to do one better. We can track all of Joe's body parts and then Tracker will plot the center of mass for us. I used a table (from Oregon State) that I originally saw on the Dot Physics Blog for the distribution of mass in bodies. I ended up finding the acceleration of Joe while in the air to be -9.824 m/s/s (about 0.18% error).

Tracker is free and works on Windows, OS X, and Linux.