The velocity vector is affected by both magnitude and direction changes in acceleration because velocity is the rate of change of position with respect to time. Acceleration, on the other hand, is the rate of change of velocity with respect to time.
When acceleration acts on an object, it can cause changes in both the magnitude (speed) and direction of the velocity vector. If the acceleration is in the same direction as the velocity, it will increase the magnitude (speed) of the velocity, resulting in faster motion. If the acceleration is in the opposite direction to the velocity, it will decrease the magnitude (speed) of the velocity, resulting in slower motion.
Additionally, if the acceleration acts perpendicular to the velocity vector, it can change the direction of the velocity without changing its magnitude. This happens when an object undergoes circular motion, where the acceleration is directed towards the center of the circle, causing the object to continuously change its direction of motion while maintaining a constant speed.
On the other hand, the position vector of an object is not affected by changes in acceleration. The position vector simply describes the displacement or location of an object with respect to a reference point, and it does not depend on the object's velocity or acceleration. Changes in acceleration do not alter the position vector directly; they only affect how the object's velocity and direction of motion change over time.