The Effect of Spin Down on Fly Ball Trajectories
Faculty Sponsor(s)
Joelle L. Murray
Subject Area
Physics/Applied Physics
Description
The flight of a spinning baseball is affected by aerodynamic forces that depend strongly on angular velocity. Although many baseball trajectory models assume constant spin, real baseballs experience a gradual reduction in spin, known as spin down, due to aerodynamic torque. This reduction in angular velocity changes the lift on the ball through the Magnus effect, modifying the trajectory and flight distance. This study develops a computational model combining translational and rotational dynamics to investigate how spin down affects the flight behavior of fly balls. The model uses a velocity-dependent drag force and a lift coefficient that depends on both velocity and spin, along with realistic atmospheric effects. Spin down is modeled through an aerodynamic torque relationship, allowing the angular velocity to decrease throughout flight. Simulated trajectories with spin down are compared to a constant spin model to quantify differences in flight behavior. The results show that while spin down has a measurable effect on fly ball trajectories, its overall influence is relatively small compared to other factors affecting flight distance and trajectory shape.
Recommended Citation
Morrill, Logan N., "The Effect of Spin Down on Fly Ball Trajectories" (2026). Linfield University Student Symposium: A Celebration of Scholarship and Creative Achievement. Event. Submission 40.
https://digitalcommons.linfield.edu/symposium/2026/all/40
The Effect of Spin Down on Fly Ball Trajectories
The flight of a spinning baseball is affected by aerodynamic forces that depend strongly on angular velocity. Although many baseball trajectory models assume constant spin, real baseballs experience a gradual reduction in spin, known as spin down, due to aerodynamic torque. This reduction in angular velocity changes the lift on the ball through the Magnus effect, modifying the trajectory and flight distance. This study develops a computational model combining translational and rotational dynamics to investigate how spin down affects the flight behavior of fly balls. The model uses a velocity-dependent drag force and a lift coefficient that depends on both velocity and spin, along with realistic atmospheric effects. Spin down is modeled through an aerodynamic torque relationship, allowing the angular velocity to decrease throughout flight. Simulated trajectories with spin down are compared to a constant spin model to quantify differences in flight behavior. The results show that while spin down has a measurable effect on fly ball trajectories, its overall influence is relatively small compared to other factors affecting flight distance and trajectory shape.