The negative shows that the acceleration is pointed towards the center of the circle (opposite the radius), hence it is called centripetal (i.e. center-seeking).
A streetcar turnaround and bus lane was carved from the center of the circle, and a $7,000 bus and streetcar terminal occupied the western portion of the site.
It becomes sensible from an initial quiescence or emptiness (wuji, sometimes symbolized by an empty circle), and continues moving until quiescence is reached again.
