I think that this is the proper place for this, but move it if I'm wrong. I'm conducting a physics project that has to do with what I think is the coriolis effect and simple harmonic motion. If a free swinging pendulum is let swing from a point over a level sand pit, as it swings, it will leave trails in the sand. But the trails are not a linear, back and forth motion. The pendulum swings back and forth within a circlular pattern, making equal periods as it swings. I'm pretty sure this has something to do with earth's rotation, but im not sure what. Questions 1: What exactly is the coriolis effect? 2: Is the coriolis effect making the pendulum swing in a circle? 3: From what i can find, the coriolis effect has nothing to do with earth's rotation directly, but a rotating frame of reference. Is this applicable to earth's rotation? 4: Is there any background information that would be cool to apply or include in this presentation? 5: Any other cool project ideas that have something to do with simple harmonic motion would be appreciated. Thanks, -savedbynails Oh, BTW, I'm also looking into doing an almost completely computer-generated presentation on something to do with either Time dialation, plasma, nuclear physics, or something neat with sub-atomic particles. Any ideas for this would also be greatly appreciated.