Which statement correctly describes speed, velocity, and acceleration?

• A. Speed is a scalar describing how fast an object moves; velocity includes speed and direction; acceleration is the rate of change of velocity.
• B. Speed is a vector that includes direction; velocity is the distance traveled; acceleration is distance divided by time.
• C. Speed measures distance only; velocity measures direction only; acceleration measures speed only.
• D. Speed and velocity are the same; acceleration is the change in speed over time.

Answer: (A)

Understanding these quantities starts with scalar versus vector: speed is how fast, without direction; velocity adds the direction; acceleration tells how velocity changes with time. The description that speed is a scalar describing how fast an object moves; velocity includes speed and direction; acceleration is the rate of change of velocity aligns with these definitions. This means velocity is a vector that can point in a specific direction and has a magnitude (speed), while acceleration measures how that velocity is changing—whether the object speeds up, slows down, or turns. The other statements mix up these ideas—for example, treating speed as having direction, or saying velocity is just distance traveled, or defining acceleration as distance divided by time—so they don’t accurately describe how speed, velocity, and acceleration relate.