where does the kinetic energy come from for magnetic attraction/repulsion?

Question

I understand the basics of magnetism; charge, fields, etc, but I don’t understand how a magnetic field can apply force seemingly forever.

For example, if I bring a magnet close to another magnet, that other magnet will eventually be drawn to the magnet in my hand, causing it to move. That kinetic energy “is caused by the magnetic attraction” but how?

If I keep my hand between two magnets, they will squeeze against my hand for seemingly forever. If I were to squeeze my own hand, I’ll get tired eventually from the exertion, but magnets don’t “get tired.” Are magnets somehow infinite energy machines? I’d assume they aren’t, but where is this energy coming from and why does it seem endless?

Edit: yes I understand the difference between “force” and “energy,” defining those terms doesn’t actually answer my question!

In: Physics

Answer 1

Adding to what people have said, energy isn’t force. In fact mechanical work, the definition of energy, is achieved by pushing a force through a certain distance. So if you have a 1 Newton weight being held down by gravity, there won’t be an exchange of energy until you start lifting that weight or let it fall against gravity. Lifting it 1 meter near the surface will cost 1 Joule of energy (and doing it in 1 second would have required the use of 1 watt of power.)

Gravity is a good force to demonstrate with, because it’s purely attractive and therefore easier to understand conceptually. If you consider that [gravity drops off with the inverse square] (https://chart-studio.plotly.com/~adelsbergc17/197/force-of-gravity-vs-separation-distance-both-masses-are-fixed-at-20kg.png) at long distances, and also consider that work/energy is defined as force integrated over some distance, you can actually find the total amount of energy that a gravity well can give a specific object in question. By getting the area under this curve all the way out to a distance approaching infinity where the attractive force becomes zero, it becomes apparent that this energy is finite. If you fire a bullet from a point mass which has this much energy, it will be slowed by gravitational pull until it comes to a complete halt at an infinite distance. This is referred to as escape velocity.