Predictions of criticality in inverted water columns

Columns of water in inverted containers, such as upside-down glasses of water, are classic phenomena that demonstrate the effects of atmospheric pressure. This paper presents an analytical method to explore the role of liquid bridges and the associated capillary forces in the equilibrium condition and the criticality of water columns held in inverted containers by a cover sheet. This method has been validated by comparing with experimental data and previous methods. Furthermore, we found that the cover sheet was not separated from the water column, but instead fell together with it, during the drop. The analytical calculation shows that the water is prone to flow out with the glass half full of water, and the cover sheet is prone to attach to a wider or a shorter glass. Furthermore, we found the conditions for pressure balance of the cover sheet and of the water column are different. The cover sheet does not fall down due to differences in pressure between the upper and lower surfaces. The static balance of the water column in the glass is dependent on balancing the additional pressure due to the surface tension of the water.