In this work, we propose an interesting combination of the Atwood machine and Galileo's inclined plane to study quantitatively kinematics with a smartphone and the phyphox app. For this purpose, we use the optical stopwatch function, based on the photosensor of the smartphone. The choice of phyphox app has some advantages for presenting the concepts of kinematics to lower high school students, as it directly and wirelessly provides analysed data to the screen of a laptop or a desktop computer. Thus, eliminating the need to export the raw data and necessitating the demanding step of data processing by the young pupils.