Final answer:
A car moving steadily around a traffic island is accelerating due to a continuous change in direction, representing a change in velocity, despite maintaining a constant speed.
Step-by-step explanation:
While a car moving around a traffic island at a steady speed of 20 mph may maintain a constant speed, it is still experiencing acceleration because acceleration is defined as a change in velocity, and velocity is a vector quantity that includes both speed and direction. Because the car is constantly changing direction while moving around the traffic island, the direction component of its velocity is changing, which by definition means it is accelerating. This is a concept in physics known as centripetal acceleration, which is directed towards the center of the circular path that the vehicle is following.