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Homework Help: Boyancy Problem

  1. Apr 7, 2005 #1
    What in am doing wrong? I assumed it's just the volume of the tank and then you find the weight of the water displaced. It's not working. I made sure that the diameter was changed into a radius for the volume of the sphere. Also as a sanity note, if you have a tank that sinks when it's empty it should still sink if it's full of air right?
    Last edited: Apr 7, 2005
  2. jcsd
  3. Apr 7, 2005 #2


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    It's really simple.
    a)[itex] F_ {APXIMN\Delta N\Sigma} = V_{sphere}\rho_{water} g [/tex]

    That's the scalar.

    For point b),apply Newton's second law for the sphere.How many forces act on the batiscaph?

  4. Apr 7, 2005 #3
    Yeah which is why I hate it when I get these problems wrong.:) I know that has to be the answer. I can't figure out why Im not getting the right number. Here is what I am getting. 1108353.888 Newtons.
  5. Apr 7, 2005 #4
    Dex why are you writing hieroglyphs for very simple formulas :bugeye: .

    Adam, [tex]F_B = \frac{4}{3}\pi r^3\rho_{w}g = F_B = \frac{4}{3}\pi (6m)^3(1000kg/m^3)(9.8m/s^2) = 8.87 * 10^6 N[/tex].
  6. Apr 7, 2005 #5
    Yeah. Your equation is right. Though don't you need to divide the diamter by two to get the radius? I checked neither of those two possible solutions are correct.
    Last edited: Apr 7, 2005
  7. Apr 7, 2005 #6
    The problem I did like this used

    \Sigma F_{y}=F_{b}-F_{t}-F_{g}\\F_{g}=ma

    with gravity and tension in the negative y direction.
    Last edited: Apr 7, 2005
  8. Apr 7, 2005 #7


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    Ramollari,the radius is 3m...:wink:

    Hey,hieroglyphs are from ancient Egypt.Those were capital Greek letters...Hey,you are Greek!! :rofl:

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