Speed

* Scalar quantity: It only has magnitude (how fast).

* Example: 50 mph, 10 meters per second.

* Doesn't care about direction. A car traveling at 50 mph east is moving at the same speed as a car traveling at 50 mph west.

Velocity

* Vector quantity: It has both magnitude and direction.

* Example: 50 mph east, 10 meters per second north.

* Direction is crucial. A car traveling at 50 mph east has a different velocity than a car traveling at 50 mph west.

The Connection

* Speed is the magnitude of velocity. Think of it like this: velocity is the complete picture, and speed is just one part of that picture (how fast it's going).

* If an object is moving at a constant speed in a straight line, its speed and velocity are numerically the same. For example, if a car is traveling at 50 mph east, its speed is 50 mph and its velocity is 50 mph east.

* If an object is changing direction, its speed and velocity will be different. Imagine a car going around a circular track at a constant speed. While its speed remains constant, its velocity is constantly changing because its direction of motion is constantly changing.

In Summary

Speed tells you how fast something is moving, while velocity tells you how fast something is moving and in what direction.