Consider a stationary observer at a railway station who sees a passenger in a railway coach that is in motion at constant speed in a straight and horizontal track. Which of the following best describes the frames of reference from which both the observer and the passenger describe each other's motion?
The observer at the railway station is in a non-accelerating frame of reference since they are stationary. They would describe the passenger's motion as moving relative to themselves.
The passenger in the railway coach is also in a non-accelerating frame of reference since the coach is in motion at a constant speed. They would describe the observer's motion as stationary relative to themselves.
Therefore, the frames of reference from which both the observer and the passenger describe each other's motion are non-accelerating frames of reference.