Inertia is a how much a stationary object resists any change in its motion. As long as all the forces acting on an object are balanced, the object does not move. Thus only an unbalanced force can move a stationary object. The amount of force needed depends on the object’s inertia. An unbalanced force applied to the car changes it state of motion. Inertia is a how much a moving object resists any change in its motion, such as a change in direction, increasing or decreasing its speed or stopping it.