Acceleration is the measure of how much a vehicle’s velocity changes with time, considering both speed and direction. If a vehicle moving in a straight-line speeds up, it is considered accelerated. Even if a vehicle moves at a constant speed in a circular motion, it is still considered accelerated because its direction is continuously changing. For any other type of motion, both changes in speed and direction contribute to acceleration.
Acceleration is a vector quantity since it has both magnitude and direction, just like velocity. To calculate acceleration, divide the change in the velocity vector by the time interval. Instantaneous acceleration is the limit of the ratio of the change in velocity to the time interval as the time interval approaches zero. The unit for acceleration is expressed in meters per second per second if velocity is expressed in meters per second.