How high are those bleachers? How fast did you throw that ball? Study gravity, acceleration, height and velocity by throwing this educational tool in any direction. A digital timer measures the amount of time the ball is in the air and automatically stops when the ball impacts a soft surface. Timer displays times from 0.01 to 29.99 seconds. Includes stand, activity guide, batteries and an instructor’s guide with instructions, background information and a student activity. 3¾" dia.