All Problems

Liquids. Capillary effects

Problem 2.175

Two glass discs of radius \(R=5.0 \mathrm{~cm}\) were wetted with water and put together so that the thickness of the water layer between them was \(h=1.9 \mu \mathrm{m}\). Assuming the wetting to be complete, find the force that has to be applied at right angles to the plates in order to pull them apart.

Reveal Answer
F=2πR2α/h=0.6kNF=2 \pi R^{2} \alpha / h=0.6 \mathrm{kN}