Here's why:

* Newton's Second Law of Motion: This fundamental law of physics states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. In mathematical terms:

* F = ma (Force = mass x acceleration)

* Net Force: This is the overall force acting on an object, considering all forces acting on it. If the forces balance out, the net force is zero, and there is no acceleration. If the forces are unbalanced, there is a net force, resulting in acceleration.

Examples:

* Pushing a box: You apply a force to the box, causing it to accelerate.

* Gravity: The Earth's gravity pulls on a falling object, causing it to accelerate downward.

* Friction: Friction opposes motion, and can act as a force that decelerates an object.