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Proportional relationships

  1. Jun 14, 2010 #1
    I was wondering if there are place on the internet where I can find a list of basic physics proportional relations.
    For example, a proportionaln relationship is that B (magnetic field strength) is directly proportional to I (current) and inversely proportional to R (distance).
    also, something like distance traveled is directly proportional to average speed.
    I just need a list of all these basic physics proportional relationships.

    Thanks so much!!
  2. jcsd
  3. Jun 15, 2010 #2
  4. Jun 15, 2010 #3
    Everywhere a formula shows things multiplied or divided, but there is no square, square root, trig function, etc.

    Suppose ABCDE=FGHIJ

    For any given value of ABCD, and any given value of FGHI, E is proportional to J. If you double one, you would double the other.

    For any given value of ABCDE and any given value of FGH, I is inversely proportional to J. On you double one, the other would become one-half its former value.
  5. Jun 15, 2010 #4
    thx bp ppsy
  6. Jun 15, 2010 #5


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    I strongly suggest you read what mikelepore said, because you might be setting yourself up for a possible confusion if you think that there is a SET collection of such a thing. For example, look at Ohm's Law


    Is V proportional to I? Or is V proportional to R? Both are correct if the other variable is kept constant. So already you have two proportionality relationship here. It gets more involved if the equation is more complicated, such as the thin lens equation

    1/f = 1/i + 1/o

    Can I say that 1/f is proportional to 1/i if I keep o constant? etc.. etc.

    It is better to learn the equation and to know what it means, and then learn how one deduce a proportionality based on what quantities are being varied and what are being held constants.

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