Describe in what way the position of the modeled point varies from the center of mass point. Specifically, in the last frame, in what direction does it lie from the center of mass point? Assuming the variation is due to small inaccuracies in the initial velocity values in the table, how would you have to modify the initial vx and vy values to get closer to the observed motion?

Now, refer to the Tracker Help to see how to define an analytic model in the Model Builder. There, you’ll need to:

Create an Analytic Particle Model
Select a color for this measurement different from the four other measures (like a bright blue)
Enter the mass of the snowboarder in kg. (See the first frame of the video for that information.)
Enter the initial time. Since we’re modeling the projectile motion part of the run, begin with time t = 0.0.
Enter the expressions you developed in (c) above for the horizontal and vertical displacements. Note that you’ll need to use symbols similar to those used in a spreadsheet for multiplication (*), division (/), and exponents (^).
After you create your analytic model, run the video. Due to the short time intervals in this video (0.1 seconds) and the difficulty of measuring closer than a couple of centimeters for any point on the snowboarder’s body in the video, the instantaneous velocities recorded in the table for any given point might be off by as much as 10 centimeters per second (0.1 meters/second). This is really just a measurement variation of one centimeter on the snowboarder’s body in the 0.1 second time interval. If a point measurement is off by one or two pixels in this video, you’ll see that much variation in instantaneous velocity for an individual point.