Impact of Drag and Spin on Baseball Flight
Understanding how drag and spin influence the flight of a baseball is crucial in explaining phenomena like why fly balls carry better to center field and how sidespin affects distance. Sidespin reduces distance by increasing drag, which competes with lift generated by backspin. The dependence of sidespin on spray angle influences the shift in trajectory towards the pull side or straightaway center field. Exploring the aerodynamics involved sheds light on the complex physics behind baseball trajectories.
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Presentation Transcript
How Do Drag & Spin Affect the Flight of a Baseball? Alan M. Nathan, @pobguy Dept of Physics, University of Illinois 1. Why do fly balls carry better to CF? 2. What is role of drag in home run rates? 1
What Does Fly Ball Distance Depend On? Physics 101 EV and LA Physics 301 Drag D Backspin lift D Sidespin hook or slice D Physics 501 Life is more complicated Magnus v Spin Drag gravity 2
1. Why do fly balls carry better to CF? Evidence from Statcast 2016-2019 Trackman data only covered stadiums only well-tracked balls The underlying physics involving baseball aerodynamics ball-bat collision 3
Sidespin Reduces Distance Why? 4
Sidespin Depends on Spray Angle Hook OPPO PULL Slice Why? Why shift to pull side? 5
Therefore Distance Depend on Spray Angle PULL OPPO 6
Some Actual Trajectories, RHH -100 00 +250 -250 7
Questions I Need To Answer For fixed EV, LA, backspin Why does sidespin reduce distance? Why does sidespin depend on spray angle? Why the shift to pull side? Or why slice to straightaway CF? 8
Why does sidespin reduce distance? Primary reason: Drag increases with spin For backspin, increased drag competes with increased lift Drag Spin Rate 9
Why does sidespin reduce distance? Primary reason: Drag increases with spin For backspin, increased drag competes with increased lift Adding sidespin with fixed backspin increase drag, reduces distance 10
Why does sidespin reduce distance? Secondary Reasons all subtle Magnus-vs-Spin is nonlinear adding sidespin increases Magnus but it reduces the lift contribution to Magnus As direction changes due to sidespin Some of backspin gyrospin, reducing lift Some of sidespin topspin or negative lift Magnus Spin 11
Some Evidence from Pitch Data: Sidespin reduces vertical movement Lift Sidespin 12
Why Does Sidespin Depend on Spray Angle? I. Horizontal Bat Angle 00 -450 450 f f 13
Why Does Sidespin Depend on Spray Angle? I. Vertical Bat Angle Pure Backspin Backspin+Slicing Sidespin 14
Sidespin vs. Spray Angle Hook OPPO Slice PULL Two Competing Mechanisms Net results Zero sidespin at 100 to pull side CF slices 15
2. What is the role of drag in HR rates? 16
Analysis Technique Use June 2019 data to model pHR vs launch parameters EV, LA, Generalized Additive Model Apply model to 2018-2021 launch parameters Find predicted pHR Expected pHR if no difference in carry Compare with actual pHR Actual/Predicted = effect of carry 17
Actual Predicted Launch Parameters 9/21 6/19 Carry Home Run Rate Drag Actual/Predicted: carry 18
Results & Conclusion After controlling for launch parameters, monthly differences in HR rates largely due to differences in drag Drag coefficient: A property of the ball Air density: A property of environment 20
Summary & Outlook We have an improved understanding of the role of spin & drag in determining fly ball distance Role of sidespin and physics thereof Role of drag in home run rate Things that keep me busy: Improved trajectory calculator Improved bat-ball collision model Why do some wood bats outperform others? I m ready to answer questions! 21
