Here's why:
* Motion is the change in position: The fundamental definition of motion is that an object is moving if its position changes relative to a reference point.
* Speed is one aspect of motion: Speed tells you how fast something is moving, but it doesn't tell you the direction.
* Direction matters: An object can be in motion even if its speed is constant, as long as its direction is changing. Think of a car driving in a circle at a constant speed. It's still moving, but its direction is constantly changing.
Therefore, motion encompasses both changes in speed and changes in direction.
