Among the more bizarre incidents that can occur in baseball is when a practised fielder struggles to catch an apparently simple “pop-up” – a ball that flies almost vertically off the bat. Now a picture of how the ball travels through the air explains why it can be so tricky.
By modelling forces such as the strike of the bat and air resistance, a team led by Alan Nathan at the University of Illinois, Urbana-Champaign, and Terry Bahill at the University of Arizona, Tucson, calculated the various trajectories that a pop-up can take.
A normally struck baseball follows a parabolic path.…
