zetetic56

I think you're right. I was thinking the same thing. But, if this is the case, then I end up in a different theoretical problem. The two bodies start out at relative rest in this frame and so there is a total of 0 momentum. When the electromagnet starts to accelerate (from left to right) there is an increase in positive momentum. And if momentum is always conserved, which it is, then there must be an equal offsetting increase in negative momentum (from right to left) at the same time. But if there is a delay between when the permanent magnet starts to accelerate and when the electromagnet starts to accelerate then, as far as I can tell, momentum is then not conserved. There seems to be a problem here, and that's why I posted this question.

An electromagnet and a permanent magnet are at a distance from one another and are at rest relative to one another. The electromagnet is off. The electromagnet is turned on. The turned-on electromagnet is within the permanent magnet's magnetic field, and so the electromagnet is attracted to the permanent magnet. (The electromagnet and the permanent magnet are attractively aligned.) And so, the electromagnet will begin to accelerate towards the permanent magnet. When the electromagnet is turned on a magnetic field is created around the electromagnet. The permanent magnet is within the electromagnet's newly created magnetic field, and so the permanent magnet is attracted to the electromagnet. And so, the permanent magnet will also begin to accelerate towards the electromagnet. --- When does the permanent magnet begin to accelerate? At the same time as the electromagnet begins to accelerate or After the electromagnet begins to accelerate --- (The curved lines in the drawings are just meant to be something symbolic of a field being present. The electromagnet's magnetic field extends beyond the full body of the permanent magnet.)