Study of the influence of air on the falling motion of bodies: a comparison between theoretical prediction and experimental data using the Tracker

This article describes a practical activity proposal for graduation, involving a theoretical and experimental study on the influence of air on the falling motion of bodies. For this, the dynamics of the movement of spherical objects in vertical fall in the air were analyzed, considering the drag force, appreciating the relationship between a characteristic time interval and the behavior of speed and acceleration, comparing the prediction of the theoretical model with the experimental data. To obtain the data, a test was performed using video footage of the fall with a cell phone and subsequent treatment with the Tracker. The results showed that the falling movement of a spherical styrofoam body with a diameter of the order of two centimeters would serve the purpose, allowing to verify the presence of inertial drag and the tendency to a limit speed in a fall of less than three meters, in according to theoretical predictions. In addition, it was found that there is no correlation between the initial velocity module and the magnitude of the terminal velocity, implying that the transition from the viscous to the inertial regime, in the first moments, would not affect the behavior of the velocity in the following moments.

Keywords
Physics teaching; Air fall; Terminal speed; Drag force; Air resistance; Viscosity