* Newton's Second Law of Motion: The correct statement is: The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. In simpler terms, the more force you apply to an object, the faster it accelerates. The heavier the object, the slower it accelerates with the same force.

* Deceleration: Deceleration is simply acceleration in the opposite direction of the object's motion. So, an unbalanced force can cause acceleration (including deceleration) depending on the direction of the force relative to the object's motion.

* Unbalanced Force: An unbalanced force is a net force that results in a change in an object's motion. It's not just about slowing down.

Here's how to think about it:

* Force in the direction of motion: An unbalanced force in the same direction as the object's motion causes acceleration (speeding up).

* Force opposite to the direction of motion: An unbalanced force in the opposite direction of the object's motion causes deceleration (slowing down).

* Force perpendicular to the direction of motion: An unbalanced force perpendicular to the object's motion causes a change in direction.

In summary:

Newton's Second Law of Motion describes how force, mass, and acceleration are related. While it doesn't explicitly mention "deceleration," it's a specific case of acceleration where the force acts to reduce the object's speed.