Helps students to visualize and grasp Newton’s Second Law of Motion. This sturdy unit demonstrates that a horizontally projected ball and vertically dropped ball land at the same time. With a detachable rod for clamping to a table or stand. This spring device can propel a ball to 48″ from its starting point. Instructions provided. (12″ x 4-1/2″ x 2″; 1.21Ibs).