What is acceleration?

• A. Velocity
• B. Speed
• C. Distance
• D. Change in velocity

Answer: (D)

Acceleration is the rate at which velocity changes over time. It happens whenever something speeds up, slows down, or changes direction, because in each case the velocity vector is altered. For example, a car turning a curve at the same speed is still accelerating because its direction—and thus its velocity—changes. Remember, velocity includes both speed and direction, while speed is only how fast something is moving and distance is how far it travels. So acceleration is best understood as the change in velocity over time.