When a stone is tied to a string and whirling in a circle, its velocity at any instant is tangent to the circular path at the point where the stone is located. This means that the stone’s velocity is directed in the direction it would continue moving if it were to break free from the string at that exact point. The velocity changes direction continuously as the stone moves along the circular path, but its speed remains constant, assuming the motion is uniform. This is an example of uniform circular motion, where velocity’s direction constantly changes.