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Homework Help: A Thermodynamic (supposed to be easy) Problem

  1. Sep 15, 2010 #1
    1. The problem statement, all variables and given/known data

    A steel tank of cross sectional area 3 m2 and height 16 m weighs 10,000 kg and is open at the top. We want to float it in the ocean so that it is positioned 10 m straight down by pouring concrete into its bottom. How much concrete should we use?


    2. Relevant equations



    3. The attempt at a solution

    I have thought about Potential gravity. I have looked that Waters density is 997 kg/m3. I got this container's ensity (It is 208.33) but I just don't know how to solve it! :) I don't remember much about buoyancy and Bouyancy might be the thing needed here!

    Answer is 19910 kg.....Please help! :)
     
  2. jcsd
  3. Sep 15, 2010 #2
    ¿you need to have 10 meters down water and 6 up water?

    Then you have to put inside the tank same weight as the weight of water evacuated. (Arquimides)

    Volume of the tank inside water (section X 10 m) ---> Volume of water evacuated ----> density of water -----> mass of water evacuated = 10000kg of the tank + x kg of concrete

    ¿It can be?
     
  4. Sep 15, 2010 #3
    30 m^3 of tank ------> 30 m^3 of water ----- x 997kg/m^3 -----> 29910 kg

    Then your tank have to weight 29910; 10000 of the tank and 19910 of the concrete
     
  5. Sep 17, 2010 #4
    Awesome!! THanks sooo much!! :)
     
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