Here's why:

* Newton's First Law of Motion (Law of Inertia): This law states that an object at rest will stay at rest, and an object in motion will stay in motion at a constant velocity, unless acted upon by a net force.

* Net Force: The net force is the overall force acting on an object. When forces are balanced, the net force is zero.

* Zero Net Force: With no net force, there is no acceleration. Acceleration is the rate of change in velocity. So, if the net force is zero, the velocity remains constant.

Examples:

* A book sitting on a table is balanced by the force of gravity pulling it down and the normal force from the table pushing it up. The book remains at rest.

* A car driving at a constant speed on a straight road has its forward force from the engine balanced by friction forces (air resistance and rolling resistance). The car continues moving at a constant velocity.

In short, when forces are balanced, the object experiences no change in its motion.