I received an assignment from my professor which sounds like follow: "Suggest a motor which operates only on magnets and gravitational force." While I did make a search online and found some model which seems to work, I am sill a little skeptical (There are videos online, but none of them are authentic). Are there any design which full fills such requirement, and has been verified? I was told that such machine would not violate the 2nd Law of Thermodynamics because the magnet itself is the energy source. Can anyone verified / debunk this? Thanks in advanced.