From the moment the rock is released until the moment it plops into
the rapids below, its acceleration is constant. The magnitude of the
acceleration is unique to the planet on which the rock is dropped,
and points toward the center of the planet. On Earth, the magnitude
is about 9.81 m/s² .
Since the size of the acceleration is not zero, that tells us right away
that the speed of the rock grows steadily as it falls.