What is defined as the speed and direction of an object's motion?

Velocity is defined as the speed and direction of an object's motion. It is a vector quantity, meaning it has both magnitude and direction. For example, if a car is traveling at 60 kilometers per hour to the north, its velocity specifies not just how fast it is moving (60 km/h) but also the direction in which it is moving (north). This is crucial in physics because understanding both aspects allows for better predictions and calculations regarding the motion of objects.

In contrast, speed only refers to how fast an object is moving without regard to the direction of motion. Acceleration is the rate at which velocity changes over time, and force is an interaction that changes the motion of an object, but neither incorporates both speed and direction as a combined concept like velocity does. Thus, velocity uniquely captures the essential idea of an object's motion in both speed and directional terms.