Which of the following best describes the difference between $velocity$ and $speed$?

• A. $Velocity$ is a vector quantity that includes both magnitude and direction, while $speed$ is a scalar quantity that only has magnitude.
• B. $Velocity$ and $speed$ are identical and can always be used interchangeably.
• C. $Speed$ is a vector quantity that includes direction, while $velocity$ is a scalar quantity.
• D. $Velocity$ and $speed$ are both scalar quantities and only differ in their units.

Answer: (A)

Verified step by step guidance

1. Understand the definitions of speed and velocity: Speed is a scalar quantity that measures how fast an object is moving regardless of direction, while velocity is a vector quantity that includes both the speed and the direction of motion.
2. Recall that scalar quantities have only magnitude (a numerical value), whereas vector quantities have both magnitude and direction.
3. Recognize that speed is the magnitude of velocity, meaning speed is the absolute value of velocity without considering direction.
4. Note that because velocity includes direction, two objects can have the same speed but different velocities if they move in different directions.
5. Conclude that the key difference is that velocity is a vector (magnitude and direction) and speed is a scalar (magnitude only).