Determining the 3D Spin Axis from TrackMan Data

When a baseball travels through the air, it experiences various forces that determine the trajectory. The most familiar of these forces is the downward pull of gravity FG. Less familiar are the aerodynamic forces, namely the drag force FD and the Magnus force FM . The drag force, or in everyday language “air resistance,” is due to the fact that the ball has to push the air out of the way. Rather than talk about the forces, it is more convenient to talk about the accelerations, since those are actually measured by the tracking systems; they are related to the forces by Newton’s famous Third Law F = ma. The conventional way to express the drag acceleration aD is through the expression ~aD = −KCDvv̂ , (1)