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Magnets strength/repel, total movement?

  1. Jan 15, 2012 #1
    Hey guys.

    Not a homework question.

    If two magnets have the same friction, same mass, etc. But have different strengths. and they are arranged so that they will repel each other, how will they move in relation to their starting points?

    Will they both move 1/2 the distance of the combined force?
    Will the weaker magnet move the distance of stronger - weaker force?

  2. jcsd
  3. Jan 15, 2012 #2
  4. Jan 15, 2012 #3

    that is what I thought.

    So... if two magnets are held in a position of repulsion by some device, and the device restricts movement in one direction but not in the other, would it move?
    Last edited: Jan 15, 2012
  5. Jan 15, 2012 #4


    Staff: Mentor

    Yes, that is how a motor works.
  6. Jan 15, 2012 #5


    User Avatar
    Gold Member

    You mean like if two people stood face to face and pushed each other away, yet one was standing against a wall would the other one move? Yes.
  7. Jan 15, 2012 #6
    Like that, but with a chain between the people.

    two magnets connected together. Held at an initial position where they will repel each other. But limited in that they can only move in one direction.

    So (wall) (magnet +++) string (+++ magnet)
  8. Jan 16, 2012 #7
    It's a force equilibrium, both bodies receive the same force :)

    Edit: I just drew the problem; actually, they don't. If one is stronger, then the other is experiencing a greater force. Wouldn't it therefore make more sense that one is displaced more than the other if they have the same mass and coeff. of friction?
  9. Jan 16, 2012 #8
    That's what has me confused.

    I think the main issue would be getting movement while being attached.

    The equivalent scenario that I am looking for would be this. If something has a mass of x, and can theoretically throw part of it's body in a given direction, at a set force, to achieve momentum, how much force would be required to move mass x?

    Say superman threw a massive rock on a chain and then just hung on to the chain, I would assume superman would move in the direction of the rock.
  10. Jan 16, 2012 #9
    ^ no that is incorrect. When the chain tightens up, both the rock and superman will stop.

    You need to study basic physics and it will all be clear.
  11. Jan 16, 2012 #10


    Staff: Mentor

    This would be a violation of Newton's 3rd law which states that the force is equal and opposite.
  12. Jan 22, 2012 #11
    Yes, of course, I forgot the reaction :grumpy: Thanks!
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