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Lift force?

  1. Sep 22, 2015 #1
    We all know the lift force in case 1, what about case 2 ? IMG_4271.JPG
     
  2. jcsd
  3. Sep 22, 2015 #2

    Orodruin

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    Note that there is also a force from the liquid pushing down on the additional wings you put in ...
     
  4. Sep 22, 2015 #3
    Buoyant force depends only on the amount of water displaced, not the shape of the object displacing it.
     
  5. Sep 22, 2015 #4

    SteamKing

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    If by "lift force", you actually mean "buoyancy", this can be calculated for case 2, although it is slightly more complicated than case 1.

    Remember Archimedes' Principle:

    https://en.wikipedia.org/wiki/Archimedes'_principle

    Note: in technical use, "lift force" is usually reserved for a force which is created by a dynamic situation, like the lift generated by an airplane's wings when flying.
    OTOH, "buoyancy" usually refers to a force created by a static situation, like the displacement of fluid by a floating object.
     
  6. Sep 23, 2015 #5
    Thank you for answers,

    ?????????? To calculate the resultant force is possible, but i wonder distribution of force. ??????????
     
  7. Sep 23, 2015 #6
    Every point on the submerged surface of the object feels a normal force proportional to the pressure at that depth ## \rho g h ##
     
    Last edited: Sep 23, 2015
  8. Sep 23, 2015 #7

    Orodruin

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    A force can never equal a pressure, the dimensions are different. An area element is subjected to a normal force equal to the pressure multiplied by the area
     
  9. Sep 23, 2015 #8
    Thank you all.

    ------------------SOLVED------------
     
  10. Sep 23, 2015 #9
    I wanted to steer clear of elemental areas for the sake of clarity but I take your point; I have amended 'equal' to 'proportional'.
     
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