What factor changes when an object accelerates?

When an object accelerates, it experiences a change in speed and velocity. Acceleration is defined as the rate of change of velocity over time, which means that as the object speeds up or slows down, its speed changes. Additionally, if the object changes direction while maintaining a constant speed, its velocity is also changing because velocity is a vector quantity that includes both speed and direction.

This understanding highlights the direct relationship between acceleration and both speed and velocity. For instance, if a car accelerates from rest, its speed increases, and thus its velocity changes in both magnitude (speed) and direction if it is turning. Acceleration, therefore, inherently implies a change in either or both of these aspects.

While the mass of the object remains constant unless acted upon by an external force (according to Newton's second law of motion), the direction can change as part of the acceleration process, but it is the combined effect on speed and velocity that correctly represents how an object's state changes due to acceleration. Therefore, recognizing that both speed and velocity are affected during acceleration is critical in understanding motion in mechanics.