Ball on the Edge

Abstract

While performing a simple kinematics experiment that involved rolling a ball off the edge of a table, many of my students observed a systematic error. Specifically, the horizontal component of the ball's velocity when it hit the floor was measured to be consistently higher than the initial velocity it had at the edge of the table. As we increased the initial speed of the ball, effect disappeared. The repeatable nature of the observation demonstrated that what we were seeing was real. Presented here is a discussion of the problem using an analysis accessible to students taking an algebra-based physics class.