): ! if a person runs around a track that is in the shape of a circle at 5 m/s without

Because the person is changing direction

Explanation:

The acceleration of an object is defined as the rate of change of velocity:

where

is the change in velocity

is the change in time

We must keep in mind that velocity is a vector, consisting of a speed and a direction. Therefore, a change in velocity means:

- either a change in the speed of the object, or

- a change in its direction

In this problem, the person is running around the track with a constant speed. However, his velocity is constantly changing (because the track is circular), this means that the change in velocity is not zero, and so there is a non-zero acceleration.