Suspend a magnet on a pendulum above a repelling magnet

  • #1
Hi, I was pondering a question after seeing a video about chaotic magnetic pendulums.

If you were to suspend a magnet on a pendulum above a repelling magnet, would it stop moving or would you get perpetual motion?

My guess is it would stop moving but I cant think of how. Gravity would try to pull the pendulum to the center put the repelling force of the magnet in the center would prevent it from stopping there. I dont see it stopping at a certain angle if the friction on the attachment point of the rod is low, thus creating perpetual motion.

I'm an arborist by profession (no more physics involved than judging wich side of the tree is heavier and where its gonna land when I cut it down) and I have a feeling I'm overlooking something obvious here because so many attempts at perpetual motion machines have been made and none seem to work.

I hope someone here can (and I certainly think someone can) awnser my question before I go out building myself some silly sience experiment to lead myself to an obvious conclusion.

Thanks in advance and sorry for my butchered English.
 

Answers and Replies

  • #2
DrClaude
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My guess is it would stop moving but I cant think of how. Gravity would try to pull the pendulum to the center put the repelling force of the magnet in the center would prevent it from stopping there. I dont see it stopping at a certain angle if the friction on the attachment point of the rod is low, thus creating perpetual motion.
It will eventually stop at angle. Since there is not a single equilibrium point, the pendulum will be very sensitive to any vibration or air flow, and may appear to keep moving, but that doesn't make it perpetual motion.
 

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