'perpetual motion' is ruled out of the realm of possibility because of which law of thermodynamics?

Answer 1

That depends on the design of the machine. Any design will violate at least one law of thermodynamics (1st, 2nd, or 3rd). Having said that, most people think that it is the 1st or 2nd law that would have to be violated in designing a perpetual motion machine. The first law states that the energy output of a machine, system or process cannot exceed the energy input. The 2nd Law states that entropy increases in all processes so the work output is always less than the energy input. Some of the energy that enters a system is wasted increasing its entropy (disorder).