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Homework Help: Match on water sustained by surface tension

  1. Aug 16, 2015 #1
    1. The problem statement, all variables and given/known data
    A match of length l=4cm is floating on the surface of the water from a glass. ( the water is at room temperature) If from on one side of the match we pour a few drops of soap, the match starts moving. In which direction is the match mooving and what force is acting upon it? ( sigma (water) = 73 mN/m ; sigma (soap) = 43 mN/m)

    2. Relevant equations
    F= sigma * l

    3. The attempt at a solution
    The force acting on the match is F= (sigma water - sigma soap) * l. I don't fully uderstand how the phenomenon is going on ... could someone draw what's happening in this problem ?

    thank you!
     
  2. jcsd
  3. Aug 16, 2015 #2

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  4. Aug 16, 2015 #3
    towards the pure water
     
  5. Aug 17, 2015 #4

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    What causes that?
     
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