Here's why:

* Balanced forces mean that the forces acting on an object are equal in magnitude and opposite in direction.

* Acceleration is a change in velocity (speed and/or direction).

* Newton's First Law of Motion states that an object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

In other words, balanced forces cancel each other out, resulting in no net force. Without a net force, there is no acceleration.

Think of a tug-of-war where both teams pull with equal force. The rope doesn't move because the forces are balanced.