The acceleration of gravity g can be computed by measuring the drop distance and the fall time. The apparatus consists of a release mechanism that also acts as the start switch, a switch plate that acts as the stop switch, and conducting balls. The release mechanism and the switch plate are both connected to the Student Timer (not included).
The release mechanism has two contact plates that are shorted when the conducting ball being measured is in place and ready to drop. The steel ball is held in place by a spring-loaded neodymium magnet. Pushing the trigger will cause the ball to drop away from the contact plates, thus opening the counter start circuit just as the fall begins. When the ball hits the switch plate, the timer is stopped.