8 (e) Acceleration
Whenever an object’s speed increases, the object accelerates. Just as objects can speed up, they can also slow down. This change in speed is sometimes called deceleration, or negative acceleration.
Even an object that is traveling at a constant speed can be accelerating. Recall that acceleration can be a change in direction as well as a change in speed. Therefore, a car accelerates as it follows a gentle curve in the road or changes lanes. Runners accelerate as they round the curve in a track. A softball accelerates when it changes direction as it is hit.