In kinematics, which statement correctly describes how speed and velocity differ?

• A. Speed and velocity are the same quantity; the terms are interchangeable in physics.
• B. Speed includes direction, while velocity is only the magnitude of motion.
• C. Speed can be negative, while velocity is always nonnegative.
• D. Speed is a scalar (magnitude only), while velocity is a vector with both magnitude and direction.

Answer: (D)

Verified step by step guidance

1. Understand the definitions: Speed is a scalar quantity, which means it only has magnitude (how fast an object is moving) without any direction.
2. Recognize that velocity is a vector quantity, meaning it has both magnitude and direction (how fast and in which direction the object is moving).
3. Note that because speed is scalar, it cannot be negative; it is always zero or positive, representing the size of the velocity vector.
4. Since velocity includes direction, it can be positive, negative, or zero depending on the chosen coordinate system and direction of motion.
5. Therefore, the key difference is that speed measures only how fast an object moves, while velocity describes both how fast and in what direction the object moves.