Sonic gravimeter for determining the acceleration of gravity: A laboratory experiment for undergraduate students

This paper deals with the measurement of the acceleration of gravity as part of an Experimental Physics Laboratory experiment for undergraduate students. The acceleration of gravity (g) has been commonly determined measuring the travel time of a body by means of a simple pendulum or objects in free fall. However, the use of mechanical or electronic chronometers as well as other devices may generate experimental errors. A prototype for determining such a parameter has been developed. Its operating principle is based on the uniformly accelerated rectilinear motion through the free fall of two bodies. The proposed prototype allows recording the sound caused by the impact of two bodies (steel balls) when falling on a solid surface. The analysis of the signal produced by the sound is made using MATLAB. When graphing the signal, the student can observe two peaks generated by the sound of the impact of each ball when impacting the metal surface for the first time. Knowing the height and sample time, the student can calculate the acceleration of gravity experimentally. Results obtained with the device described have been compared with the theoretical ones.