BHS ->Physics -> Mechanics -> Kinematics -> this page
The concepts of velocity and acceleration are linked together, but they are linked incorrectly in many people's minds. Many people think that if an object has a large velocity, it must have a large acceleration - if it has a small velocity, it must have a small acceleration - if its velocity is zero, its acceleration must be zero, too. THIS IS WRONG!!
Acceleration is the rate at which velocity changes, which means that acceleration tells you how fast the velocity is changing. A large acceleration tells you that the velocity is changing quickly - a small acceleration tells you that the velocity is changing slowly - an acceleration of zero tells you that the velocity is not changing at all.
Acceleration tells you how the velocity changes - it doesn't tell how how much the velocity is! An object can have a large velocity and a small (or zero) acceleration - and vice versa.
Many people also have the misguided notion that "positive acceleration means speeding up, negative acceleration means slowing down." Sorry! By studying the examples of calculation accelerations, you can conclude that: