Here's why:
* Speed is the rate at which an object covers distance. It's a scalar quantity, meaning it only has magnitude (like 10 mph).
* Velocity is the rate of change of an object's position over time. It's a vector quantity, meaning it has both magnitude and direction (like 10 mph north).
When an object moves in a circle, it maintains a constant distance from the center, so its speed is constant. However, its direction is constantly changing as it travels around the circle. Since velocity requires both speed and direction, the object's velocity is constantly changing, even if its speed remains the same.
Example:
Imagine a car driving around a roundabout at a steady 20 mph. The car's speed is constant, but its velocity is constantly changing because its direction is constantly changing as it circles the roundabout.
