I think I've already posted this but it didn't come up. Sorry if this is a simple question, but I've never done physics before: I came up with this at about 11:45 PM. I was sitting at my computer desk playing with my metal ruler. It had a little hole near the end and I had my finger through it and was letting it drop from different angles, as I had nothing better to do. I noticed that when I dropped it from 90 degrees from my computer desk, it would swing 135 degrees back from the starting point and then swing back to the middle of both points at 45 degrees from the table. I then held it at 135 degrees from the table and let it drop and it swung back to 180 from the starting point and then came back to the middle at 90 from each point. I did this holding it at 270 degrees and the same thing happened: it came back to the middle. I confused as to why, at different starting points did it always change instead of them all just swinging to 180 degrees. Is there some type of formula for this? Thanks for your help.