A question about perpetual motion machines. Now, I know you might think this belongs in Pseudoscience, but my question is about the physics involved, so... Is the concept of a perpetual motion machine, and the concept of it being impossible, all about a device which continually operates without power input or about a device which has greater than 100% mechanical efficiency? The reason I ask is that a couple of years ago I saw this little gizmo made in a Swedish university. It was a round metal track with magnets in it. Tow high sides and two low sides. A ball bearing rolled around it, up east, down south, up west, down north (just using those directions to designate the sides). The makers said that gravity, and the magnets assisting on the upward climb after each fall, kept the ball bearing rolling around the track continuously until someone stopped it. Then you just set the ball rolling again. I don't know if this works or not, but it seems reasonable enough. However, unless a coil was set in the centre and that ball was quite ferro-magnetic, I can't see any way to gain any power (or any useful amount of power) out of it. So, is the entire thing about: A) Producing something that keeps going? or B) Producing something that keeps going and has >100% power efficiency?
"all about a device which continually operates without power input" it certainly can't be that there's always input required, whether you understand the input or not is irrelevant, it must be there
The ball would eventually stop. There is some heat generated as the ball rolls along the track. There is some friction, however little, between the ball and the track. The heat energy is taken from the total kinetic energy and slowly whittles it away like life points in the old-school Gauntlet game for NES.
Perpetual means it keeps itself going. It can't have >100% efficiency because that means the output energy > input energy. In case of the steel ball the output energy is kinetic (its motion) and the input is kinetic from (being pushed). This would go against concervation of energy and we all knew that.Please Register or Log in to view the hidden image!
Simpsons Quote "In this house we obey the laws of thermodynamics!" --Homer Simpson, in response to Lisa's perpetual motion generator
