In physics, the three types of acceleration are changes in speed, direction and both simultaneously. The word "velocity" is often used in place of speed. A person can calculate the acceleration of an object by determining its velocity and the length of time it accelerates.
When a car makes a sudden turn, it experiences an increase in acceleration, even if its speed remains constant. This increase in acceleration can be felt through the jerking effect that is imposed on the passengers' bodies. In addition to regular acceleration, an item can experience negative acceleration, which is characterized by a decrease in speed. The intended direction of an object may remain positive regardless of its velocity rate.