In this work we develop a physical model which describes the behavior of an unsteady flow measured with a gravimetric set up. The model is based on equation for the physical shape of the interfaces between different fluids in the beaker (air-oil and oil-water) and on models of contact angles between these interfaces and the tube and beaker wall. In these models a dynamical contact angle is considered which can change with motion of the interfaces and which depends on velocity of the interfaces. The full report can be downloaded here.