The Force Between Two Sheets of Glass Separated by a Thin Film of Water

Pure water and clean glass attract each other. If two flat circular plates of glass are separated by a film of water, both plates of glass will be attracted to the water and a force will be required to pull them apart. The water will curve in between the plates of glass at both ends because of surface tension forces and the pressure inside the water film will be lower than atmospheric pressure.

Since the films of water is concave in one direction and convex in the other the pressure difference is given bywhereis the surface tension of water.

The forceis then given by

Surprisingly large forces can be produced. Ifand the thickness of water isthen withwe have

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