Smartphone usage has expanded dramatically in recent years worldwide. This revolution also has impact in undergraduate laboratories where different experiences are facilitated by the use of the sensors usually included in these devices. Recently, in several articles published in the literature, the use of "smartphones" has been proposed for several physics experiments. Although most previous articles focused on mechanical experiments, an aspect that has received less attention is the use of "rotation sensors" or "gyroscopes." Indeed, the use of these sensors paves the way for new experiments enabling the measurement of angular velocities. In a very recent paper the conservation of the angular momentum is considered using rotation sensors. In this paper we present an analysis of the rotational energy of a physical pendulum.