Study of rotational motion by a fidget spinner and smartphone

Recent studies on rotational motion have been conducted using a fidget spinner and a smartphone. Experimental results have been described by models based on Newton's second law, taking into account the resulting resistive torque acting on the system. In the present paper, we investigate repeatability (within a device) and reproducibility (between devices) in an experiment on rotational motion using modified fidget spinners and a smartphone. We report the results obtained for different spinners of the same type, i.e. with the same model of ball bearing. By fitting the experimental data with the analytical solution of Newton's equation of motion, we determine the Coulomb friction torque and the drag coefficient that affect the motion of the system. Furthermore, we show that comparing multiple devices enables learning outcomes that are not accessible in single-setup experiments. Students can compare devices, quantify repeatability and reproducibility, and critically discuss model limitations, uncertainty propagation, and experimental variability. The proposed activity, designed to explore rotational motion using modified fidget spinners and a smartphone, can be carried out in undergraduate university laboratories. Moreover, this experimental activity enables students to learn physics concepts, such as angular velocity and moment of inertia, by performing simple and meaningful experiments in the classroom.