Study on the Apparent Weight of Hourglass Caused by Sand Flow

Due to the acceleration of the sand centroid, the hourglass's apparent weight will change slightly with time in the process of sand flow, which is the sum of the effects of each part of the sand in the hourglass. By establishing an hourglass model, in this paper we can get the relationship between the centroid position vector of each part of the sand and the time, and then get the time-dependent acceleration of the overall centroid of the sand. According to the shape of the hourglass itself and the parameters of each part, the process of sand flow can be devided into five stages. Then the mismatch between theoretical and experimental values is analyzed, and the imperfect elastic collision between sand and the bottom of the hourglass is used to explain and further revise the previous theory.