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Homework Help: Archimede's Principle help

  1. Apr 26, 2005 #1
    My professor briefly went over Archimede's principle and assigned some problems on it. I do not know how to attack it. Here's the first problem he gave:

    A Ping-Pong ball has a diameter of 3.80 cm and average density of 0.084 g/cm^3. What force is required to hold it completely submerged in water?
  2. jcsd
  3. Apr 26, 2005 #2


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    The buoyant force is equal to the weight of the water displaced by the ball. You can find that by figuring out the volume of the ball and multiplying by the density of water. The net force on the ball is its little bit of weight, plus you pushing it down, plus the buoyant force, and those add up to zero.
    Last edited: Apr 26, 2005
  4. Apr 26, 2005 #3

    Doc Al

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    Start by identifying all the forces acting on the ball, including the applied force. One of those forces is the buoyant force, which Archimede's principle says is equal to the weight of the displaced water. (The buoyant force is the force that the fluid--water, in this case--exerts on a submerged object.)
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