Speed

* Definition: How fast an object is moving. It only tells us the magnitude (how much) of the movement.

* Units: Meters per second (m/s), kilometers per hour (km/h), miles per hour (mph), etc.

* Example: A car traveling at 60 mph.

Velocity

* Definition: How fast an object is moving *and* in what direction. It includes both magnitude and direction.

* Units: Same as speed, but always include direction.

* Example: A car traveling at 60 mph *north*.

Acceleration

* Definition: The rate at which an object's velocity changes over time. It describes how quickly an object speeds up, slows down, or changes direction.

* Units: Meters per second squared (m/s²), kilometers per hour squared (km/h²), etc.

* Example: A car accelerating from 0 to 60 mph in 5 seconds.

Key Differences and Relationships

* Speed vs. Velocity: Velocity is speed with direction.

* Acceleration and Velocity: Acceleration is the *change* in velocity over time. If velocity is constant, there is no acceleration.

* Constant Speed vs. Constant Velocity: A car traveling at a constant speed of 60 mph in a straight line has a constant velocity. But a car traveling at a constant speed of 60 mph around a curve is accelerating because its direction is changing.

In summary:

* Speed: How fast.

* Velocity: How fast and in what direction.

* Acceleration: How quickly velocity changes.