Determination of the Friction Coefficient of an Inclined Plane Using the Doppler Effect and Smartphones

A phone emitting sound of a fixed frequency is sliding on an inclined plane and approaching a second phone kept at the bottom of the plane. The detected frequency versus time data by the second phone are used to calculate the acceleration of the sliding phone. The primary objective of this paper is to calculate the sliding friction between the phone and the plane from the acceleration values. It demonstrates that the sliding friction is constant irrespective of the inclination of the plane. Results are in good agreement with the one obtained from the video analysis.