The use of video analysis for the study of motion and forces is well established in the worlds of physics and biomechanics. The issue of parallax error, sometimes referred to as perspective error or scaling error, when videotaping a moving object is known, and the experimenter is often counseled to be "far away." However, "far…

Early in their study of one-dimensional kinematics, my students build an algebraic model that describes the effects of a rolling ball's (perpendicular) collision with a wall. The goal is for the model to predict the ball's velocity when it returns to a fixed point approximately 50-100 cm from the wall as a function of its velocity as it passes…