Yep, uh-huh, indeed, indubitably, and you better believe it.
The ball did accelerate.
Acceleration means any one of these:
-- speeding up
-- slowing down
-- changing direction .
The direction of the ball changed from east to west.
That's acceleration right there.
_____________________________________
Acceleration means any change of velocity.
Velocity is speed and direction.
The velocity of the ball changed from (40 km/hr east) to (40 km/hr west).
The change in velocity was 80 km/hr to the west.