The Physics Behind Gaussian Guns

[gaz3992]

I'm sorry this is not really a school question i was just intrigued and did not now where else to ask about it. I have seen videos of these Gaussian guns and they appear to generate energy from nowhere, obviously impossibly. So what is the physics behind how they work?

 

[Tusike]

I'm sure you know about that pendulum thing that has e.g. 5 balls in a row, and if you lift one up at one end, and let it go, after colliding only the one on the other side will start to move (Newton's pendulum; google search will give you images right away).
Well, this is almost exactly the same. Those magnets are very strong, and the metal ball that gets pulled to them gets a lot of energy from the magnetic field. This energy is then transferred from the magnet to the other balls, just like in that pendulum thing. The magnetic field is pretty weak by the last ball, so it is easily overcome by that ball, which is then fired out with ease.