So, I've done a little reading (Physics Made Simple, etc,) and most recently consulted with a physics professor who happens to be in the family. As a result, I'm fairly (if not completely) convinced that creating a realistic pendulum is well beyond what 5th graders could do. I'm not even sure if I'll ever be able to complete the project myself. I have learned a lot about pendulums, gravity, etc. I realize now that my pendulum does not reflect reality because it moves at a steady rate through it's swing when, in fact, a pendulum accelerates in its downward motion and decelerates in its upward motion. In order to simulate reality I need to be able to change the rate of acceleration of the heading of my pendulum. I now have a formula that would accomplish this, however, it includes a square root function. Is that possible in the etoy environment?