Weight of an hourglass—Theory and experiment in quantitative comparison

10.1119/1.4973527.2 A flowing hourglass changes its weight in the course of time because of the accelerated motion of its center of mass. While this insight is not new, it is frequently said that the effect is tiny and hardly measurable. Here, we present a simple experiment that allows the monitoring of weight as a function of time, and that shows that there are different stages of the weight variation. The experimental result is in quantitative agreement with theory.