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Basic Surface Tension Problem

  1. Nov 7, 2014 #1
    1.
    Calculate the force needed to move the wire in the figure (Figure 1) if it holds a soapy solution (surface tension is 0.025 N/m) and the wire is 16.0 cm long.

    Express your answer to two significant figures and include the appropriate units.

    giancoli_cp7.ch10.p67.jpg


    2.

    γ(surface tension) = F (force) / l (length)

    3. My attempt at a solution

    γ=F/l so γl=F

    γ: 0.025 N/m

    l: 16cm or 0.16m

    0.025 N/m * 0.16m = 0.004 N or 4.0 * 10-3N

    I know this must be ridiculously easy but I really can't figure out what I'm missing here. Do I need another equation to solve this problem? Am I messing up the units somehow?
     
  2. jcsd
  3. Nov 7, 2014 #2

    RonL

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    Gold Member

    I can't help at this time, but someone will pretty soon:) I just have time to say welcome to PF and hope you stay around and get to know some people:D
     
  4. Nov 7, 2014 #3
    Look very carefully at the second part of the figure.

    Chet
     
  5. Nov 7, 2014 #4
    Got it. Thank you!

    I knew it must be something simple like that but I was getting hung up because I just could not visualize exactly what this thing is supposed to look like.
     
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