Clever device for numerous collision/friction/gravity experiments. The four-position, spring-trigger device allows for controlled and repeatable force applications to the 1" steel balls and/or friction block. Place one ball at the trigger and the other four balls in the center of the track. What happens when the ball is fired into the other four balls? What happens with more force? What if two balls are fired? Elevate the track and determine what effect gravity and/or friction has on the descent of a ball. You will design many experiments to use with this device. Comes assembled with five steel balls and one friction block.