Acceleration can be defined as the rate at which velocity

Answer here

Acceleration can be defined as the rate at which velocity is changes by an object.

Explanation:

Acceleration is a quantity of vectors which is characterized as the rate at which an entity shifts its velocity. An object accelerates when its velocity is shifting. The acceleration unit is meters per second squared. As velocity is a speed and a direction, two methods from which one can accelerate: change your speed or change your direction or change both.

If one don't change its pace and also donot change its direction then he or she simply won't be able to accelerate, no matter how quickly one go. Therefore, a jet traveling at a constant speed of 800 miles per hour along a single direction has zero acceleration, although the plane goes very fast, as the speed is not increasing.