For a basic school project, I'm making a rube goldberg (when you push a marble and a ton of things happen to accomplish one simple goal). I've made two long rods, and put a sphere ontop of them. I then applied gravity to the ball.

Here is where I'm stuck. I remember learning something about passive and active rigid bodies, but I'm not sure what to do. I want the ball to roll down the two rods (they are close to each other, I want this all done in dynamics). The rods are already angled enough, but right now all the ball does is fall though the rods.

Eventually the ball will roll down, then land in a bowl, which will pull a string to knock over another marble that will knock over dominoes etc etc.

Thanks a ton for the help!