What is required to change an object's state of inertia?

To change an object's state of inertia, an unbalanced force is required. Inertia refers to an object’s resistance to changes in its state of motion, including both speed and direction. According to Newton's first law of motion, an object at rest stays at rest, and an object in motion remains in motion at a constant velocity unless acted upon by an unbalanced external force.

An unbalanced force is one that is not being countered by equal force in the opposite direction. For example, if a car is at a stop and you push it (applying an unbalanced force), it will begin to move. Similarly, if a moving car encounters an unbalanced force, such as friction from the road or a collision, its speed or direction will change.

The other options do not effectively change an object's state of inertia. Since inertia is inherent to the object, a balanced force simply results in no change in motion as the forces acting on the object are equal and opposite, canceling each other out. Meanwhile, frictional force, while it can create an unbalanced force, is a specific type of force that can diminish motion but does not itself define the general requirement for changing inertia.