The radius vector \vec{r} represents the position of a particle relative to an origin at a specific time, with its derivative indicating the particle's velocity. As the particle moves, both the velocity and the angle of the radius vector can change, reflecting the dynamic nature of its trajectory. In a circular motion scenario, while the radius remains constant, the velocity vector is tangent to the circle, demonstrating that it does not align with the radius vector. Additionally, the acceleration required for circular motion points radially inward toward the center. This illustrates the complex relationship between position, velocity, and acceleration in particle motion.