* Net Force: For an object to move, there needs to be a net force acting on it. This means the sum of all forces acting on the object must be non-zero. If forces are balanced, they cancel each other out, resulting in no motion.

* Static Equilibrium: An object at rest is said to be in static equilibrium. This means the net force on the object is zero, even though forces might be acting on it. A book sitting on a table is an example. Gravity pulls it down, but the table pushes back with an equal and opposite force.

* Inertia: Objects at rest tend to stay at rest, and objects in motion tend to stay in motion at a constant speed and direction. This is known as inertia. To overcome inertia and start an object moving, a net force is required.

Examples:

* Pushing a heavy box: If you push a heavy box with a force equal to the force of friction holding it back, the box won't move. The forces are balanced.

* A hanging picture: The picture is at rest, even though gravity is pulling it down. The tension in the string holding it up is an equal and opposite force.

In summary: Forces can cause motion, but only if the net force acting on an object is not zero.