How the forces on a drop of water versus mercury on a glass slide influence the shape?

  • #1
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I am trying to understand how fluids form particular shapes when put on a solid.
  1. In the two figures,what are we taking as a system for the forces?
  2. How the resultant of the forces influences the shape of the different fluids?
 

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  • #2
BvU
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Hi,

Do not erase the template ! You have already found something, so start from there!
 
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  • #3
haruspex
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I am trying to understand how fluids form particular shapes when put on a solid.
There are two parts to this:
- the forces that result in the contact angle
- the forces that control the shape of the surface elsewhere
Are you interested in analysing both of those or just one?
For the latter, consider a horizontal slice at some height. Can you relate the surface tension, the curvature and the internal pressure? (Are you familiar with the analysis of pressure in bubbles?)
 
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  • #4
There are two parts to this:
- the forces that result in the contact angle
- the forces that control the shape of the surface elsewhere
Are you interested in analysing both of those or just one?
For the latter, consider a horizontal slice at some height. Can you relate the surface tension, the curvature and the internal pressure? (Are you familiar with the analysis of pressure in bubbles?)
I am Interested in determining the system on which the forces are acting and how the forces influence the contact angle of the drop.(I.e why liquid forms a specific contact angle due to resultants of all forces acting on it?)
 
  • #5
haruspex
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I am Interested in determining the system on which the forces are acting and how the forces influence the contact angle of the drop.(I.e why liquid forms a specific contact angle due to resultants of all forces acting on it?)
I might have been of help with the shape elsewhere but I know little about contact angles.
Have you read this https://en.m.wikipedia.org/wiki/Contact_angle?
 
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  • #7
haruspex
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You can write what ever you know about shape of drops,I will like to learn it as well.
Consider a horizontal disc of the drop, height y, thickness dy, radius x.
What equations can you write relating the these to y', y", density, surface tension etc?
 

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