Yes it is. The ball is undergoing accelerated motion. Uh huh. You bet it is.
"Acceleration" does NOT mean "speeding up". Acceleration is "change of velocity", and 'velocity' is speed AND direction. If speed or direction changes, velocity changes, and that's 'acceleration'.
If the ball is traveling in a circle, then its direction is continually changing. Its motion is constantly accelerated. Even if its speed never changes.
