Measurements are presented on the drag and lift coefficients for three relatively smooth balls
launched in air and tracked with two cameras separated horizontally by 6.4 m. The ball spin was
varied in order to investigate whether the Magnus force would increase or decrease when the ball
spin was increased. For one ball, the Magnus force increased. For another ball, the Magnus force
decreased almost to zero after reaching a maximum. For the third ball, the Magnus force was negative
at low ball spins and positive at high ball spins. For one of the balls, the ball spin increased
with time as it travelled through the air.