Surface Tension of wood on water

[zorro]

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.

 

[Andy Resnick]

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.

 

[zorro]

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?

 

[Andy Resnick]

Canthotaxis is a great word! It refers to the pinning of a contact line at a sharp edge: the contact angle can vary by an amount proportional to the angle subtended by the solid edge.

http://books.google.com/books?id=IO...d=0CB0Q6AEwAg#v=onepage&q=canthotaxis&f=false