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Need help with explaining surface tension

  1. Apr 5, 2006 #1
    My group is to teach a lesson to our AP Physics class on a lesson from our book. We got lesson 92, which deals with Viscous Fluids, Surface Tension, and Elastic Properties of Solids. Since theres 3 people, we each got one and lucky me got surface tension. I have to be able to discuss this pretty darn throughly, explaining anything about it. I see that theres an equation, gamma = F/L Answer being in N/m 's

    I have some info from my book but there is these force diagrams that i have NO clue how im going to explain, and maybe thats why i think i dont understand this. It gives an example of a needle on top of water. Needle weights .008 N so whats the max. ^ force of the water....it would be .001. This force diagram shows a Tx on both sides of the needle 2 Ty's up and to T's going at feta angle. I dont get that. I understand everything else. Where are all these forces coming from?

    Ok, maybe im making this too complicated...or undercomplicating it. Im not sure. Can someone give me a general info on surface tension so that they can solve problems dealing with them and i not sound like a total moron when up in front of the class?

    Thanks in advanced, sry for such a long post..
  2. jcsd
  3. Apr 5, 2006 #2


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  4. Apr 5, 2006 #3


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    The force in surface tension arises from the intermolecular (or interatomic) bonds in the liquid phase of a two phase system. These same forces are responsible for viscosity.

    As FredGarvin recommended, Hyperphysics is a good starting point.

    For a stable bubble, the force created by the gas pressure (inside the bubble) must balance the tension at the surface of the bubble, which is really the interface between gas (or vapor) and liquid phases. The tension has to be in the liquid because there is not contiguous bonding in a gas.

    The tensile force also acts tangent (parallel) with the surface of the liquid. Where the bubble attaches to a solid surface, there is interatomic bonding between liquid and solid.
    Last edited: Apr 5, 2006
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