What is defined as a change in position over a period of time?

The correct answer is that change in position over a period of time is defined as velocity. Velocity specifically refers to the rate at which an object changes its position and includes both the speed of the object and the direction in which it is moving. This distinction is important, as velocity is a vector quantity, meaning it has both magnitude (speed) and direction.

In contrast, speed only measures how fast an object is moving, without regard to its direction, and is therefore a scalar quantity. For example, if a car is traveling at 60 miles per hour, that figure represents speed, but not velocity, because it lacks information about the car's direction.

Acceleration refers to the rate of change of velocity over time, which can involve changes in speed or direction. Displacement, on the other hand, describes the change in position of an object but does not include the time component necessary for defining velocity. Therefore, while all these terms are related to motion, velocity is specifically the one that encompasses both the change in position and the time factor.