What is acceleration defined as?

Acceleration is defined as the rate of change of velocity over time. This means it quantifies how quickly an object's velocity is changing, whether that change is an increase or decrease in speed, or a change in direction.

In physics, velocity is a vector quantity, which means it includes both speed and direction. Therefore, when we talk about the rate of change of velocity, we are considering not only changes in how fast an object is moving but also changes in the direction of its motion.

Understanding acceleration is crucial in mechanics, as it describes how objects move under the influence of forces. For instance, when a car speeds up, slows down, or turns, it is experiencing acceleration. This definition is fundamental in analyzing motion in various contexts, such as automotive performance, physics experiments, and even in everyday situations.

The other options refer to different concepts of motion, but they do not capture the essence of acceleration as the rate at which velocity changes.