In this paper, the dynamic case of a system made up of two blocks connected by a string over a smooth pulley is revisited. One mass lies on a horizontal surface without friction, and the other mass has a vertical displacement. The motion equation is obtained and its solution is determined using the Mathematica package. Also an experimental montage for this system is made and experimental data for the vertical position y in the function of time t are obtained using a data acquisition system and Tracker video analysis. The relation y vs t can be represented by a polynomial of degree six. An average relative error of 3.61(10.14)% is obtained between the theoretical results acquired with Mathematica and the data taken from Tracker (data acquisition system).Universidad de Ibagu?