Final answer:
Acceleration in physics refers to the rate of change of velocity and, in the context of projectile motion, it is always directed downward with a constant value due to gravity.
Step-by-step explanation:
When addressing the question of acceleration in different positions of motion, it is essential to understand that acceleration is the rate of change of velocity over time. It can occur as a change in speed or direction, or both. In the context of projectile motion, such as a ball being thrown, the acceleration, once the ball is in free fall, is always in the downward direction with a constant value due to gravity. This acceleration does not change and remains constant regardless of the ball's direction of motion. Therefore, the correct answer is that the acceleration is always in the downward direction and it has the same constant value.
Additionally, in scenarios such as uniform circular motion, although the magnitude of the velocity remains constant, the direction changes continuously, resulting in a sideways acceleration. The constant magnitude of acceleration in uniform circular motion ensures that there is always a net force acting in the direction of the center of the circle.