Acceleration Measurements Using Smartphone Sensors: Dealing with the   Equivalence Principle
  Acceleration sensors built into smartphones, i-pads or tablets can conveniently be used in the Physics laboratory. By virtue of the equivalence principle, a sensor fixed in a non-inertial reference frame cannot discern between a gravitational field and an accelerated system. Accordingly, acceleration values read by these sensors must be corrected for the gravitational component. A physical pendulum was studied by way of example, and absolute acceleration and rotation angle values were derived from the measurements made by the accelerometer and gyroscope. Results were corroborated by comparison with those obtained by video analysis. The limitations of different smartphone sensors are discussed. 
Mart\'in Monteiro, Cecilia Cabeza, Arturo C. Mart\'i
physics.ed-ph physics.pop-ph