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2 spheres in an ocean

  1. May 17, 2007 #1
    1. The problem statement, all variables and given/known data
    Two spheres, with volume 0.1m^3, and masses M1=200kg and M2=15kg, are connected by a thin wire. They are dropped into the ocean (assume Rho=1000kg/m^3) and allowed to sink



    2. Relevant equations



    3. The attempt at a solution
    I know buoyancy = Rho * g * V
    Buoyancy + Lift-M2 + Fwire = Sink-M1.

    I'm not sure how to get the rising/sinking forces of the two spheres, and how they interact with each other though.

    Any help at all is appreciated, thanks in advance.
     
  2. jcsd
  3. May 17, 2007 #2

    Hootenanny

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    Welcome to the forums,

    Well initially, I think it would be best if we considered each sphere independently. So, can you write two separate equations for the net force acting on each sphere?
     
  4. May 17, 2007 #3
    My best guess would be:

    Heavy (case1). mg = downwards force - buoyancy. DownwardsF = 200g - 981N = 981N?

    I'm not sure how the lighter sphere will act though. If it's specific density is lower than 1 then only part of the sphere will be submerged if it's acting seperately?
     
  5. May 17, 2007 #4

    Hootenanny

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    For the heavy one, I was thinking something more of the form (taking upwards as positive);

    [tex]F_{net} = T + \rho\cdot V\cdot g - m_{1}g[/tex]

    Where T is the tension in the string. Does that make sense?
     
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