**To calculate acceleration, divide the change in velocity by the total time.** Acceleration values are expressed in units of velocity per time, including meters per second squared.

Acceleration is a vector quantity and is defined as the rate at which an object changes its velocity. Velocity refers to the rate at which an object changes its position. People often use the term acceleration to describe someone or something that is moving at a rapid pace. However, in physics terminology, an object can be moving quickly but not accelerating. In physics, acceleration has nothing to do with speed. This is reflected in the calculation to divide the change in velocity by time, not the change in speed.

Because acceleration is a vector quantity, it must also be associated with a direction. To determine the direction of acceleration, you must first determine whether the object is increasing or decreasing in velocity and whether the object is moving in a positive or negative direction. The positive or negative direction can be determined by a simple graph. Anything to the right or up is positive, while anything to the left or down is negative. A general principle is that if an object is decreasing in velocity, then its acceleration is in the opposite direction of its motion.