Which term describes speed in a specific direction?

• A. Mass per volume
• B. The rate of change of acceleration
• C. Speed in a specific direction
• D. Distance traveled over time regardless of direction

Answer: (C)

Understanding motion in direction requires a quantity that includes both how fast and which way. Speed tells how fast something is moving, but it doesn’t specify direction. When you add a direction to the speed, you describe motion as velocity. So the term that describes speed in a specific direction is essentially velocity—the idea of speed with a chosen direction. The other options describe different ideas: mass per volume is density; the rate of change of acceleration is jerk; distance traveled over time without regard to direction is just speed.