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Force of magnets

  1. Oct 26, 2005 #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. Oct 26, 2005 #2


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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. Oct 26, 2005 #3
    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. Oct 26, 2005 #4


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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. Oct 26, 2005 #5
    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. Oct 26, 2005 #6
    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. Oct 26, 2005 #7


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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. Oct 26, 2005 #8
    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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