Paradoxical pop-ups: Why are they difficult to catch?

Professional baseball players occasionally find it difficult to gracefully approach seemingly routine pop-ups. We describe a set of towering pop-ups with trajectories that exhibit cusps and loops near the apex. For a normal fly ball the horizontal velocity continuously decreases due to drag caused b...

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Bibliographic Details
Published in:American journal of physics 2008-08, Vol.76 (8), p.723-729
Main Authors: McBeath, Michael K., Nathan, Alan M., Bahill, A. Terry, Baldwin, David G.
Format: Article
Language:English
Subjects:
Acceleration
Athletes
Physics
Professional baseball
Velocity
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Summary:Professional baseball players occasionally find it difficult to gracefully approach seemingly routine pop-ups. We describe a set of towering pop-ups with trajectories that exhibit cusps and loops near the apex. For a normal fly ball the horizontal velocity continuously decreases due to drag caused by air resistance. For pop-ups the Magnus force is larger than the drag force. In these cases the horizontal velocity initially decreases like a normal fly ball, but after the apex, the Magnus force accelerates the horizontal motion. We refer to this class of pop-ups as paradoxical because they appear to misinform the typically robust optical control strategies used by fielders and lead to systematic vacillation in running paths, especially when a trajectory terminates near the fielder. Former major league infielders confirm that our model agrees with their experiences.
ISSN:0002-9505
1943-2909
DOI:10.1119/1.2937899