Get a ping pong ball and a balloon! Put the ping pong ball inside the balloon and add some air not alot just a few breathes or so. Hold the balloon upside down so the air part is facing the ground. Squeeze the balloon once that represents a contraction. Squeeze it a few more times and the ping pong ball will start it's travel down... Representing dialation. The ping pong ball is the baby and the cervix is the air part that sticks out from the balloon itself. There is a video of it on YouTube and it's pretty cool if your into experiments.