This small group activity is designed to help upper division undergraduate students plot trajectories of objects undergoing linear acceleration in different reference frames. Students work in small groups and plot the trajectory of a ball thrown straight up as seen by a moving train undergoing constant speed and, separately, constant acceleration. The entire class wrap-up discussion reflects on the different plots students came up with, allowing students to compare trajectories of objects seen by observers in inertial and non-inertial frames.

This material is part of the Paradigms in Physics project at Oregon State University. This work promotes the use of active student learning in upper division physics courses. Both learning materials and learning strategies are provided to help both students and instructors.