  The concepts of the Coriolis and the centrifugal force are essential in
various scientific fields and they are standard components of introductory
physics lectures. In this paper we explore how students understand and apply
concepts of rotating frames of reference in the context of an exemplary lecture
demonstration experiment. We found in a $Predict-Observe-Explain$-setting, that
after predicting the outcome prior to the demonstration, only one out of five
physics students correctly reported the observation of the trajectory of a
sphere rolling over a rotating disc. Despite this low score, a detailed
analysis of distractors revealed significant conceptual learning during the
observation of the experiment. In this context, we identified three main
misconceptions and learning difficulties. First, the centrifugal force is only
required to describe the trajectory if the object is coupled to the rotating
system. Second, inertial forces cause a reaction of an object on which they
act. And third, students systematically mix-up the trajectories in the
stationary and the rotating frame of reference. Furthermore, we captured
students' eye movements during the $Predict$ task and found that physics
students with low confidence ratings focused longer on relevant task areas than
confident students despite having a comparable score. Consequently, this metric
is a helpful tool for the identification of misconceptions using eye tracking.
Overall, the results help to understand the complexity of concept learning from
demonstration experiments and provide important implications for instructional
design of introductions to rotating frames of reference.
