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Homework Help: Formula of weight of surface water

  1. Jan 14, 2016 #1
    1. The problem statement, all variables and given/known data
    Why the weight of water at water surface is given by formula 2(pi)Rσ(cos angle) ?

    2. Relevant equations


    3. The attempt at a solution
     

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  3. Jan 14, 2016 #2

    haruspex

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    Is there more context to this?
    My guess is that a capillary tube has been inserted into water reservoir, resulting in a column of water rising height h (compared with the water remaining in the reservoir). The weight of this column is held up by surface tension in the meniscus. Phi will be the angle of contact of the meniscus.
     
  4. Jan 14, 2016 #3
    how about 2(pi)R ? how it comes?
     
  5. Jan 14, 2016 #4

    haruspex

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    Surface tension is a force per unit length. What is the length of contact between the water surface and the capillary (radius R)?
     
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