Investigation of free fall using bottles of water and rocks

Galileo Galilei proposed that, in the absence of resistance from the surrounding environment, all objects fall with the same constant acceleration regardless of mass. This indicates that constant acceleration occurs across any time interval for one object, and that the overall acceleration of one object compared to another is the same, regardless of mass. In this experiment, we tested Galileo’s prediction by comparing the fall times of two identical plastic water bottles filled three-quarters of the way to the top, one with water and the other with rocks. Motion of the bottles was recorded, digitized, and analyzed. Velocity/time graphs were generated for five trials of each bottle, and acceleration was determined from the slope of the linear regression line for each trial. A two-sample unpaired t-test was used to compare the mean accelerations. The statistical analysis showed no significant difference between the accelerations of the two bottles, supporting Galileo’s theory of free fall. Any observed variation is attributed to experimental uncertainty and timing error rather than a difference in acceleration due to mass.