1. If the object has positive acceleration there is a force acting on the object to make it move. A positive acceleration means the speed of that object is increasing by the acceleration's magnitude per second. The object is said to accelerating.
2. If the object has negative acceleration, the object is decelerating. It's speed is decreasing as the force going opposite of the object increases by the negative acceleration's magnitude per second.
3. If the object has no acceleration. The object is either at rest or has a constant velocity. There may be no force acting on the object or the net force on the object is zero.
