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Homework Help: Need help on a problem

  1. Apr 3, 2008 #1
    A block with a density of 545 kg/m[tex]^{3}[/tex] and a volume of 0.645 m[tex]^{3}[/tex] is held completely under water by means of a rope. Determine the magnitude of the force of the cord on the block.

    Relevant Equations
    F[tex]_{}buotant[/tex] = [tex]\rho[/tex][tex]_{}fluid[/tex]V[tex]_{}submerged[/tex]
    Unsure about any others...

    I had no idea how to even solve or approach this problem. Much thanks appreciated!
  2. jcsd
  3. Apr 3, 2008 #2
    Draw a free body diagram. There are 3 forces acting on the block: The buoyant force, the gravitational force and the tension in the string.

    The gravitational force and the tension are in the same direction, but the buoyant force is in the other. Hence, those two forces must equal the third. Can you solve it now?
  4. Apr 3, 2008 #3
    thanks i understand the problem now
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