How Does Surface Tension Affect Pressure Between Non-Wetting Plates?

[Aias]

Homework Statement

http://ocw.mit.edu/courses/mechanic...cs-spring-2013/assignments/MIT2_06S13_ps2.pdf
Problem 7[/B]

Homework Equations

$F=2*V/(a^2)*\sigma*cos(180-\theta)$

The Attempt at a Solution

With the problem statement given, it seems like the component of surface tension in the vertical direction on the upper plate would be in the same direction as the proposed required force due to the surface being non-wetting, thus no need for an actual force F to hold the plates together. I don't see what kind of force would want to push the plates apart? I came to that equation after some fiddling around, it seems like it could be correct, but I don't have an intuitive understanding why it would be so.

 

[Chestermiller]

Homework Statement

http://ocw.mit.edu/courses/mechanic...cs-spring-2013/assignments/MIT2_06S13_ps2.pdf
Problem 7[/B]

Homework Equations

$F=2*V/(a^2)*\sigma*cos(180-\theta)$

The Attempt at a Solution

With the problem statement given, it seems like the component of surface tension in the vertical direction on the upper plate would be in the same direction as the proposed required force due to the surface being non-wetting, thus no need for an actual force F to hold the plates together. I don't see what kind of force would want to push the plates apart? I came to that equation after some fiddling around, it seems like it could be correct, but I don't have an intuitive understanding why it would be so.

As a result of the surface tension effect, is the pressure in the liquid between the plates higher of lower than the pressure of the surrounding atmosphere?

Chet