Advanced laboratory workshop on the determination of the viscosity coefficient of liquids by the Stokes method

Abstract

Introduction. In accordance with the training plan for students and cadets of higher technical educational institutions of EMERCOM of Russia, when studying Molecular Physics, the laboratory work "Determination of the viscosity coefficient of a liquid by the Stokes method" is performed. The need for this work is due to the fact that students are visually familiar with the phenomenon of transfer in liquids, since in the future, when solving problems of hydraulics and when operating fire equipment, it is necessary to take into account the viscosity of the liquid. Goals and objectives. The aim of the study is to modernize the laboratory method for determining the viscosity of a liquid by the Stokes method, since an analysis of the published descriptions of this work shows that the relative error in determining the viscosity is 15 percent or more. Methods. To reduce the error in determining the viscosity coefficient of the liquid, video recording of the ball falling in the test liquid was used, followed by graphical processing of the experimental results to calculate the constant speed of the ball and the area in which a constant speed is observed. Results and discussion. The method was tested on the example of determining the viscosity coefficient of glycerin. Examples of computer-graphical processing of the results of experiments for calculating the constant velocity of the ball falling in glycerin are given. It is shown that a tenfold deceleration of the video recording of the fall of a steel ball in glycerin practically does not affect the result of processing its position during the fall and the value of the constant velocity. A visual picture of the movement of a ball in glycerin in the center of a dimensional glass cylinder is obtained. The liquid flows around the ball in laminar mode, which makes it possible to apply the Stokes dependence for the resistance force. Conclusions. It is shown that the proposed method of optical video recording of the ball falling in glycerin allows measuring a constant rate of fall with an error of less than 0.2 %. The laboratory work on determining the viscosity coefficient of a liquid by the Stokes method has been modernized, which allows determining the viscosity coefficient with an error of less than 4 %. Keywords: viscosity coefficient, glycerin, Stokes method, laboratory technique.