1. May 2, 2009 #1

   l46kok

   

   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?

    

   l46kok, May 2, 2009
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3. May 2, 2009 #2

   dx

   

   Homework Helper

   Gold Member

   You might have read the question wrong. If p ∝ q², and q ∝ 1/r, then p ∝ 1/r².

    

   dx, May 2, 2009
4. May 2, 2009 #3

   jamesb-uk

   

   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.

    

   jamesb-uk, May 2, 2009

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