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As of now, we don’t know enough about things like spin decay, spin axis changes during flight, seam height, scuffs, and of course seam orientation to model them. We will take better data into account as more data becomes available.
For this first pass, I used a simple drag model that considers the coefficient of drag to be constant. That is, were not taking the drag crisis into account. This is a VERY simple model that needs to be refined in later iterations of the program. For now, it is sufficient for most pitched balls with the exception of something like, maybe, the Eephus pitch.
For lift from Magnus, I used the same model as Professor Nathan which comes from Rod Cross’s book Physics of Baseball & Softball. This is an acceptable model although, Jeff Kensrud at Washington State’s Sports Science Lab published a paper of the drag and lift generated by various sports balls. These results could be used to create more refined models for lift and drag. This is likely my next step.