The kind of motion where speed and direction don't change is called uniform motion.

Here's a breakdown:

* Uniform motion: An object moving at a constant speed in a straight line. This means both the speed and direction of the object remain constant.

* Constant speed: The object covers the same distance in equal intervals of time.

* Straight line: The object moves in a single, unchanging direction.

Examples of uniform motion:

* A car traveling at a steady 60 mph on a perfectly straight highway.

* A ball rolling across a frictionless surface at a constant speed.

Important Note: In real-world scenarios, true uniform motion is difficult to achieve. There are always some forces acting on objects, causing them to slow down or change direction. However, we can approximate uniform motion in many situations.