Which term describes how quickly velocity changes?

• A. Acceleration
• B. Velocity
• C. Speed
• D. Distance

Answer: (A)

Acceleration is the rate at which velocity changes over time. Since velocity includes both speed and direction, any change in either aspect— speeding up, slowing down, or turning—means velocity is changing, and that change is described by acceleration. For example, a car speeding up from rest has positive acceleration, and a car moving in a circle while keeping the same speed still experiences acceleration because its direction is continually changing. Speed describes how fast something is moving, but not how quickly that motion is changing. Velocity describes the current motion (speed with direction), not the rate of change. Distance is about how much ground is covered, not how quickly velocity changes.