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Floating sphere

  1. Jan 23, 2008 #1
    An empty hollow sphere of inner radius r, outer radius R and density p floats so that exactly one half is submerged in a fluid of density pf.
    a.) if p/pf is =3 what is the ration of r/R.

    ok well
    mg=pVg
    m=pV/2

    V=4/3pi(R^3-r^3)

    m=p(4/3pi(R^3-r^3)

    I dont know where to go from here any help is appreciated thanks.
     
  2. jcsd
  3. Jan 23, 2008 #2

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    Are you talking about the same V in the two eqns? First decide upon the symbols properly.

    Then directly apply Archimedes' Principle.
     
  4. Jan 23, 2008 #3
    no its the same equation just canceled out the g. but ya Its the same V
     
  5. Jan 23, 2008 #4

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    So, the 2nd eqn follows from the 1st? This is a matter of elementary algebra! Think again and write eqns properly.
     
  6. Jan 23, 2008 #5
    F=0
    mg-fB=0
    m=p * Vs (volume of sphere)/2

    Know for the volume i have 4/3pi(R^3-r^3)
     
  7. Jan 23, 2008 #6

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    First clear the matter of the two eqns in post #2. What do the two different V's represent? And how can eqn 2 follow from eqn 1?
     
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