Understanding Surface Tension and its Relationship to Force Calculation

In summary, the conversation revolves around the concept of surface tension and its application in finding force. The questioner is unsure about the direction and length that should be used in calculating the force exerted by surface tension. They seek clarification on the direction of the length and whether it is always oriented in the same direction with respect to the fluid surface. The conversation also touches on the concept of surface energy and non-dimensional velocity. The experts suggest providing more details for a better understanding of how surface tension is being used in the application.
  • #1
member 428835
Hi PF!

Simple question here, but if we have some fluid in, say a cylinder container, with a specified surface tension, to get force would we multiply the surface tension by the height of the cylinder (if it's standing up on a circular side)? I know we multiply it by some length, but I don't understand it enough to know which one.

Please help.

Josh
 
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  • #2
What force are you trying to find?
 
  • #3
You know, I'm not really sure. I guess what I'm really wondering is what direction that length is, since surface tension is force per unit length.
 
  • #4
Consider the concept of "surface energy." Think about that word, "surface."
 
  • #5
Yea, my though is per unit height...is this wrong? Like, orthogonal to whatever surface we are talking about?
 
  • #6
joshmccraney said:
Yea, my though is per unit height...is this wrong?
If you're trying to find the force exerted by the surface tension, height has nothing to do with it. You need to ask: Force on what?
 
  • #7
I see what you're saying. To clarify my question entirely, I am reading a paper and there is a non-dimesnional velocity term. Now I could simply take the paper's word and use their proposed velocity, but I want to work it out and see for myself that they have correctly non-dimensionalized the velocity component. They introduce the surface tension for non-dimensional purposes. I am trying to find the direction of that length that is being used. Is this length in surface tension not always oriented in the same direction with respect to the fluid surface?
 
  • #8
joshmccraney said:
I am trying to find the direction of that length that is being used. Is this length in surface tension not always oriented in the same direction with respect to the fluid surface?
When finding the force exerted by the surface tension on some line, that line is on the surface or its circumference. Perhaps if you posted more details someone will recognize exactly how the surface tension is being used in your application.
 
  • #9
https://www.physicsforums.com/search/209340/?q=surface+tension&o=relevance
 

Related to Understanding Surface Tension and its Relationship to Force Calculation

1. What is surface tension?

Surface tension is a physical property of liquids that describes the force acting on the surface of the liquid due to the cohesive forces between the molecules. It is the measure of how difficult it is to break or stretch the surface of a liquid.

2. How is surface tension measured?

Surface tension is typically measured in units of force per unit length. The most common unit of measurement is Newtons per meter (N/m). It can also be measured in dynes per centimeter (dyn/cm) or millinewtons per meter (mN/m).

3. What factors affect surface tension?

The strength of surface tension is affected by several factors, including the type of liquid, temperature, and the presence of any impurities. Generally, surface tension is stronger in liquids with stronger intermolecular forces and at lower temperatures. Impurities can lower surface tension by disrupting the cohesive forces between molecules.

4. How is surface tension related to force calculation?

Surface tension is related to force calculation because it is the force acting on the surface of a liquid. This force is responsible for the shape of a liquid's surface, as well as processes such as capillary action and wetting. To calculate the force due to surface tension, the surface tension value and the length of the surface must be known.

5. How does surface tension affect objects placed on a liquid's surface?

Surface tension has a significant impact on objects placed on a liquid's surface. The force of surface tension acts to minimize the surface area of the liquid, causing objects to float or sink depending on their relative densities. This force can also cause objects to be held together or break apart when placed on the surface of a liquid.

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