Describe motion that would represent constant acceleration due ONLY to a change in direction.

-- the motion of a point on the tire of a bicycle that's moving at a constant speed on a straight road;-- the motion of a point on the tire of a car that's moving at a constant speed on a straight road;-- the motion of a planet in a perfectly circular orbit;-- the motion of any point anywhere on any of the hands on an 'analog' clock ... a clock that has hands ... except right at the center of the clock.