Balancing the bearing track on the fulcrum, place the carts on either side of the fulcrum so that they meet at it. Using one of the masses for its smoothness, tap the trigger button on one of the bearing carts. The carts will come apart, but the track will remain balanced. This indicates that the center of mass is still over the fulcrum. Repeat the experiment after loading one of the carts with some extra mass. Balancing the track will be different this time, and the carts will move at different velocities. As the carts reach the end of the track, be careful to catch it as it tips. This will happen more suddenly when one cart is loaded and still has room to keep going after the other cart reaches the end, quickly displacing the center of mass.