INTRODUCING MOBILE APPS IN PHYSICS LABS: DETERMINING MOMENTS OF INERTIA WITH A CELL PHONE

Nowadays, mobile apps are essential tools in many secondary school and higher education physics courses. They provide easy access to a basketful of physical measurements that previously could only be performed with sophisticated equipment. Definitely, the collection of measurements that students can currently perform by their own includes, for instance, acceleration, pressure, magnetic field, sound intensity level, or light power. In this way, they gain not only in-depth knowledge on the measurement process, but also deep insight on the concepts and phenomena studied through these sensors.
As a new step in our active-learning strategies, we have introduced mobile measurements in a lab experiment aiming to determine the moment of inertia of a body. Instead of using detailed procedurally prescriptive exercises, we have provided the students with just some brief guidelines, and a set of questions to foster comprehension and discussion. Furthermore, the tedious conventional procedure of obtaining numerical data, the angular position of a constantly accelerated turntable versus time, by using a fork type light barrier in different points, has been replaced by two alternative new methods. In the first one, the video of the rotational motion is recorded with a cell phone and later on analyzed by means of a motion modeling software, such as Tracker. In the second proposal, the measurement is even more straightforward, as it is performed directly by the gyroscope sensor of a cell phone attached to the turntable, providing angular velocity versus time.
We describe here the use of the mobile apps in this experiment, and the possibilities for introducing them in similar experiments. We also discuss the pedagogical implications of using the cell phone sensors in our lab teaching and the feedback from students.