* Velocity is a vector quantity: It has both magnitude (speed) and direction.
* Speed is a scalar quantity: It only has magnitude.
Constant velocity means both speed and direction are unchanging. If the speed changes, the magnitude of the velocity changes, and therefore the velocity is no longer constant.
Example:
Imagine a car traveling in a straight line at a constant speed of 60 mph. This is constant velocity. Now, if the car starts to slow down or speed up, its speed is changing. This change in speed means the velocity is also changing, even if the car is still moving in a straight line.
In summary:
* Constant velocity implies constant speed and constant direction.
* Variable speed implies variable velocity, regardless of direction.
