Speed

* Definition: How fast an object is moving.

* Measurement: Distance traveled over a certain amount of time (e.g., miles per hour, meters per second).

* Scalar Quantity: Speed only tells you how fast something is moving, not its direction.

Velocity

* Definition: How fast an object is moving *and* in what direction.

* Measurement: Distance traveled over a certain amount of time, *and* direction (e.g., 50 mph due north, 10 meters per second to the east).

* Vector Quantity: Velocity requires both magnitude (speed) and direction.

Think of it this way:

* If you're driving a car at 60 mph, you're describing your speed.

* If you're driving a car at 60 mph *north*, you're describing your velocity.

Key Points

* An object can have a constant speed but a changing velocity. Imagine running around a track at a steady pace – your speed is constant, but your velocity is changing because your direction is constantly changing.

* An object can have a zero velocity but a non-zero speed. Imagine a runner standing still at the starting line. They have no velocity because they aren't moving, but they might have a speed of 0 mph because they are ready to start running.

Let me know if you'd like more examples!