Surface Tension of wood on water

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Discussion Overview

The discussion revolves around the effects of surface tension on a uniform cube of wood floating on water, particularly focusing on whether surface tension influences the buoyancy of the object. The scope includes theoretical considerations of buoyancy, surface tension, and the implications of perfect wetting.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that since the force of surface tension is tangential to the liquid surface, it does not affect the buoyancy of the cube.
  • Another participant proposes considering a sphere instead of a cube, noting that perfect wetting leads to a thin film of fluid covering the sphere, but the sphere can still be buoyant, although the governing parameters for film thickness are uncertain.
  • A different viewpoint indicates that perfect wetting may result in a vertical force downwards due to surface tension, suggesting that this could buoy the sphere or cube downwards, albeit slightly.
  • A participant introduces the term "canthotaxis," explaining it as the pinning of a contact line at a sharp edge, which can affect the contact angle based on the edge's angle.

Areas of Agreement / Disagreement

Participants express differing views on the impact of surface tension on buoyancy, with no consensus reached on whether it has a significant effect or not. The discussion remains unresolved regarding the influence of surface tension in this context.

Contextual Notes

There are limitations regarding the assumptions made about the shape of the object (cube vs. sphere) and the conditions of perfect wetting, which may affect the conclusions drawn about buoyancy and surface tension.

zorro
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Suppose a uniform cube of wood floats on the surface of water. Water wets it completely. Will it be buoyed up or down by surface tension?

The force of surface tension is tangential to the liquid surface (along the surface of liquid). So I think there is no effect on buoyancy of cube due to surface tension.
 
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Cubes cause problems because of the edges (canthotaxis)- let's consider a sphere instead.

Perfect wetting will result in a thin film of fluid covering the sphere, but the sphere can still be buoyant. I'm not sure what parameters govern the film thickness.
 
I guess perfect wetting will result in a vertical force downwards (due to surface tension). So the sphere/cube will get buoyed down by the water (though by a small amount)
What is canthotaxis by the way?
 

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