Newton’s law of motion for variable mass systems applied to capillarity

Abstract

The standard Newton’s equation of motion for variable masses is set up and solved to describe the time-dependent rise of a liquid in a capillary tube. The findings in the nonviscous case are also supported by quantitative estimates of the potential energy changes suffered by the interfacial films. The theoretical oscillations in the viscous case are confirmed experimentally for tubes having a radius larger than a critical value.