How is velocity best defined in physics?

Velocity is best defined as the speed of an object in a specific direction. This definition emphasizes that velocity is a vector quantity, meaning it encompasses both magnitude (how fast something is moving) and direction (the path the object is taking). For instance, if a car is traveling north at 60 kilometers per hour, its velocity conveys not just how fast it is moving, but also where it is headed, which is crucial for understanding motion in physics.

In contrast, speed alone is a scalar quantity that indicates how fast an object moves without taking into account the direction. The other choices may describe aspects of motion but do not capture the complete essence of velocity as a directional concept. Therefore, the concept of velocity integrates both the rate of motion and the directional component, making it a fundamental aspect of kinematics in physics.