Speed is the distance traveled over time. The standard unit for distance is the meter. The standard unit for time is seconds. Speed = Distance / Time
Average speed is used when speed changed twice or more. Most things that are moving change speed more than one time. Average Speed (v) = Total Distance / Total Time
Instantaneous speed is the rate of an object moving at any given time. When you look at a speedometer and see different speeds at different times, you are looking at the instantaneous speed.
Speed vs. Velocity
When graphing speed, the time goes on the horizontal axis (x-axis) and the distance goes on the vertical axis (y-axis). The line is called the slope. The slope represents the speed. Slope = Rise / Run = Y2-Y1 / X2-X1
Velocity is speed in a given direction. Velocity can change over time. Change in velocity can be caused when speed or direction changes. Arrows called vectors are used to indicate velocity.
Speed is the magnitude of velocity because speed doesn't have direction and velocity does. Velocity is a vector because it has direction and speed. When something is moving, the velocity is always changing,