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Proportionality Question

  1. May 2, 2009 #1
    1. The problem statement, all variables and given/known data
    If P is proportional to q^2
    and q is inversely proportional to r

    Show that p is proportional to r^2


    2. Relevant equations
    p = kq^2
    q = c/r

    where k and c are proportional constants


    3. The attempt at a solution

    I'd say this is impossible. This is all the information given to me. This was found in an exam paper.

    But even if we assume

    k = c

    p is not proportional to r^2.

    -.-

    Any ideas?
     
  2. jcsd
  3. May 2, 2009 #2

    dx

    User Avatar
    Homework Helper
    Gold Member

    You might have read the question wrong. If p ∝ q², and q ∝ 1/r, then p ∝ 1/r².
     
  4. May 2, 2009 #3
    p=kq^2
    q=c/r
    therefore
    p=k(c/r)^2
    or
    p=(kc^2)/r^2

    So p should be inversely proportional to r^2, with the constant of kc^2.
     
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