Low-cost experiment for measuring energy dissipation on a pendulum

In this paper we present an acquisition system of time intervals and estimates of velocity by infrared light sensors connected to Arduíno board. Because of precision in time measurements, which present uncertainty in time on the order of 10−4s, we are able to determine the damping ratio for pendulum produced by air friction in a small angles regime. We studied the physical system formed by a small glass bottle suspended by a wire. This system was modeled as different pendulum kinds, e. g., compound pendulum, simple pendulum and damped pendulum, where we discuss about validity limits of these models.