* Velocity is a vector: La vitesse ne concerne pas seulement la vitesse à laquelle quelque chose se déplace (vitesse), mais aussi dans la direction dans laquelle il se déplace. Il a à la fois une magnitude (vitesse) et une direction.

* Changing direction changes the vector: Even if the speed remains the same, changing direction means you're changing the velocity vector.

* Acceleration: Changing velocity (either speed or direction) means that the object is accelerating. Acceleration is the rate of change of velocity over time.

Exemple:

Imagine a car traveling at 60 mph east. If the car turns north while maintaining 60 mph, its speed remains the same, but its velocity changes because the direction has changed.

Takeaway clé: Velocity is a vector quantity, and a change in direction, even with constant speed, constitutes a change in velocity.