The equivalence principle comes to school: falling objects and other middle school investigations

Comparing two objects falling together is a small-scale version of Galileo's classical experiment, demonstrating the equivalence between gravitational and inertial mass. We present here investigations by a group of ten-year-olds, who used iPads to record the drops. The movie recordings were essential in the follow-up discussions, enabling the students to compare the different situations and to discern situations where air resistance was essential and where it could be neglected. By considering a number of familiar situations and simple investigations that can be performed, e.g., on a playground, students may come closer to an appreciation of the deep significance of the non-influence of mass on motion under gravity.