If the direction of a velocity vector changes while the speed (magnitude) of the velocity remains constant, it means that the object is undergoing uniform circular motion. In this case, the object's velocity vector continuously changes its direction but maintains a constant speed.
In uniform circular motion, the magnitude of the velocity remains unchanged, but its direction changes as the object moves along the circular path. This is because velocity is a vector quantity that includes both magnitude (speed) and direction.
To visualize this, consider an object moving in a circle at a constant speed. At any point on the circle, the object's velocity vector points tangent to the circle, perpendicular to the radial line connecting the object to the center of the circle. As the object moves along the circle, its velocity vector continuously changes its direction, always tangent to the circle, while the speed remains constant.
In summary, when the direction of a velocity vector changes while the speed remains constant, it indicates uniform circular motion.