Force of magnets

  1. Magnet A has twice the magnetic field strength of magnet B (at equal distance) at a certain distance and pulls on the magnet B with a force of 30N. Determine the force with which magnet B pulls magnet A.
    Could someone help me. I'm just starting physics in hs.
    Last edited: Oct 26, 2005
  2. jcsd
  3. Tide

    Tide 3,136
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    Do you have any reason to believe the forces will be different - i.e. Newton's law of action reaction does not apply?
  4. thats probably correct. this is a basic question. i think it is getting at coulombs law.

    i think the answer is 15N. not sure
  5. Tide

    Tide 3,136
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    If you're talking about magnets you're probably not dealing with Coulomb's law.

    So, why do you think the answer is 15 N?
  6. well i'm not exactly sure. i'm looking in the chapter of magnetism in my book and i don't see any forumla's. its weird. i went back a chapter and found coulombs which deals with force=(k)(q1q2)/d^2.

    i wasn't sure if it was right or now. if you could help me on a formula i could try and solve it. thanks

  7. i think because magnet a is twice as strong, that magnet b is half of its strength.

    also i forgot a few parts of the question that might help

    it has twice the magnetic field strength.
    Last edited: Oct 26, 2005
  8. Tide

    Tide 3,136
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    I have no idea what equations your textbook shows but if you have none relating the pulling force of a magnet that should be a clue for you!

    Remember Newton's Law that I mentioned earlier and think about this: If a magnet is twice as strong then not only it will it pull another with twice the force it will also be pulled with twice the force!
  9. so the answer is that since they are an equal distance away. that the force that a acts upon b is the same force that b acts upon a.

    answer 30N?
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