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    The force F newtons,between two magnetic poles is given by the formula

    F= 1/(500r^2)

    where r(m) is the distance apart.

    Find the rate of change when the poles are 0.2m apart and the distance between them is increasing at a rate of 0.03 ms^-1.





    _________________


    So, I think I want to find
    dF/dt

    Using the chain rule, that would be

    dF/dr * dr/dt

    dF/dr = -1000r^-3

    dr/dt = 0.03


    Multiplying them after substituting r for 0.2 always gives the wrong answer. HELP!
    (REally want helP, GIVE help kiNdly)
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    (Original post by Hippysnake)

    dF/dr = -1000r^-3
    Check this, I think.
    • Thread Starter
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    (Original post by Hathlan)
    Check this, I think.
    Yeah, stupid me. Thanks. (Will rep, including PM guy)
 
 
 
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Updated: July 13, 2009

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