# Perpetual motion? [duplicate]

while i was studying my Alevel physics course, i came around the term " perpetual machines " just at the end of the conservation of energy concept, anyway, as a curious person i googled " perpetual machines" and i saw lots of concepts but the one that really confused me is the " john wilkins perpetual machine " i want to ask how does it work? will it keep on forever? does it even work?

The video you see is a hoax. The principle (as explained in the video) is that the ball is attracted by the magnet ("lodestone") to go up the ramp, then drops down and slides along the bottom ramp.

There are two problems with the implementation: first, the force of a magnet on an object is a function of the gradient - and the gradient of the magnet shown drops VERY quickly with distance. The apparent "keeps rolling up the slide" you see is NOT what you expect from a ball in the field of a magnet.

Second, when you get near the top, the magnet should hold the ball firmly - there is no mechanism for making it drop down the hole (again, the force of the magnet on the ball should be MUCH stronger when it's very close)

Third - if the magnetic field is on all the time, the force is conservative: that is, after a complete loop by the ball, no net work is done by the magnet (or gravity).

The only way to explain the video is to realize there is probably a bit of electronics in the framework, and the magnetic force is modulated (turned on and off) to keep the ball rolling. Which makes for great "kinetic art", but not a perpetual motion machine.

Conservation of energy tells us that such machines cannot exist. And that is a law that has been proven right, over and over again.

• Your second point is incorrect. It is absolutely possible to arrange the setup such that the weight of the ball exceeds the force of the magnet at the top of the ramp. If it doesn't, just move the hole farther away - simple. The machine as a whole still doesn't work, though. – Nuclear Wang Apr 18 '17 at 14:46
• @NuclearWang - I am not saying it is not possible - just that in the video such a mechanism was not provided. – Floris Apr 18 '17 at 15:05