The rate of change of velocity over time is called?

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

Answer: (B)

Acceleration is the rate at which velocity changes over time. Velocity tells you how fast something is moving and in what direction, while acceleration describes how that motion is changing—whether the speed is increasing or decreasing or the direction is turning. If a car speeds up, slows down, or steers so its direction changes, the velocity vector is changing, and that change per second is acceleration. The usual unit is meters per second squared (m/s^2). Even when speed stays the same but the direction changes (like a car turning a curve), there is acceleration because the velocity is changing. Force is related because it can cause acceleration, but it’s the rate of change of velocity itself that is acceleration.