Velocity vs. Speed
* Speed is how fast an object is moving. It's a scalar quantity, meaning it only has magnitude (e.g., 20 mph).
* Velocity is how fast an object is moving *and* in what direction. It's a vector quantity, meaning it has both magnitude and direction (e.g., 20 mph to the north).
How Velocity Changes with Constant Speed
Think of a car driving around a circular track at a constant speed. Even though the car's speedometer shows a steady speed, its velocity is constantly changing because its direction is changing.
Examples
* A car going around a curve: The speed might be constant, but the car's velocity is changing because its direction is constantly changing.
* A satellite orbiting Earth: It moves at a constant speed, but its velocity is constantly changing as it changes direction to stay in orbit.
* A ball thrown horizontally: The ball's speed might be constant, but its velocity is changing because gravity is pulling it downwards, changing its direction.
Key Takeaway:
Velocity is a vector quantity, so it requires both speed and direction. A change in either speed or direction (or both) will result in a change in velocity.
