Eli5: why cant we use magnets to make an infinitely spinning thing to get infinite energy

Question

-english is not my first language-

Edit: alot of people think im referring to motors or generators or some sorts. But I mean something like this:

https://i.ytimg.com/vi/BSdSDfOWbNs/maxresdefault.jpg

I know its probably fake and not possible but I want to know why and how

In: 0

Answer 1

Magnets dont do work.

Glue a magnet to ceiling and put something hanging on magnet. It does as much energy as you screw a hook to ceiling and hang something onto it.