Here's why:

* Acceleration is the rate of change of velocity.

* Velocity is speed in a specific direction.

* Constant speed means the object is moving at the same rate without changing direction.

Therefore, if an object is moving at a constant speed and in a constant direction, it has no acceleration.

Examples:

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

* A ball rolling across a smooth, flat surface at a constant rate.

Let me know if you'd like to learn more about acceleration, velocity, or speed!