Here's why:

* Forces: Pushes or pulls on an object.

* Unbalanced forces: When the forces acting on an object are not equal in magnitude or direction, they don't cancel each other out.

* Result: An unbalanced force causes a change in an object's motion, either by starting it moving, stopping it, or changing its direction or speed.

Example:

Imagine pushing a box across the floor. You're applying a force forward, and friction is applying a force backward. If you push harder than the friction, the forces are unbalanced, and the box will move forward.