There is no such thing as Deceleration!
Well, not
technically.
Objects do not simply "decelerate," and stop, their energy is actively taken from them, and are stopped.
This is known as
Negative acceleration.
Negative acceleration is the force
applied by all things
against an object that take energy from its motion, such as friction, or a large
unmoveable object, and either re-apply it (such as the large object), or convert it to heat (friction). As such, all objects
opposing this movement apply a
negative acceleration to the object.
Say I'm going forward at 10 m/s, to stop me a force must be applied. To stop me in one second, you apply a negative acceleration of -10m/s and I'll come to an
instant halt. Unless that force is
applied (or any other force of some varying magnitude),
I'll just continue on, never stopping.