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Homework Help: Bouyant Force

  1. May 5, 2005 #1
    I need to calculate the bouyant force of a cardboard boat and the bouyant force exerted by the water. What is the equation to do this?

    Also, I need to the volume of water the boat displaces. (Density of water is 1000 kg/m^3).

    And last but not least, I need to determine the water level on the boat.

    If anyone could help me out with the equations, that'd be great. Thanks.
  2. jcsd
  3. May 5, 2005 #2

    Doc Al

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    Staff: Mentor

    Since you didn't state the problem in sufficient detail to get an answer, nor did you show what you've done so far, all I can offer are some generalities:
    (1) Archimede's principle tells us that the buoyant force on a submerged object equals the weight of the displaced fluid (in this case water).
    (2) If the boat is floating, then it must be in equilibrium: the vertical forces must balance. (What forces act on the boat?)​
  4. May 5, 2005 #3
    Sorry. We had to do a project, and make a boat out of cardboard and tape, and 2 people had to get in and paddle across a pool. Now for my lab writeup, I have to answer 3 problems, but we did bouyancy so long ago, I forgot/lost my bouyanct equations (my bad, shoulda saved them).

    1st question. Calculate the bouyant force exerted by the water on the boat for the following conditions 1) empty boat. 2) boat with occupants in

    2nd question. FOr each of the aboce conditions in calculation 1, calculate the volume of water that the boat must displace. Use a density of water of 1000 kg/m^3

    3rd question. For each of the above conditions and using your plans for your boat design, determine the water level on your boat.

    All I need are the equations and I can plug in the numbers. Thanks.
  5. May 5, 2005 #4

    Doc Al

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    Staff: Mentor

    I wonder what data you recorded.
    Assuming you measured the weight of the boat + occupants, use point #2 in my last post to answer this one.

    For this one, consider point #1 in my last post. Also make use of the definition of density: D = mass/volume.

    The volume of water displaced combined with the geometry of your boat should allow you to answer this one.
  6. May 5, 2005 #5
    I appreciate your help, but I need the equations...badly...please
  7. May 5, 2005 #6
    Nevermind, I found the equations. Thanks though.
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