Final answer:
A free-body diagram for a car should include gravity, normal force, friction, and any applied forces; each represented as vectors and excluding the net force.
Step-by-step explanation:
When creating a free-body diagram for a car, key forces to consider include gravity, which is represented by the car's weight (w), the normal force (N) exerted by the surface on the car, friction which could either oppose or facilitate the car's motion depending on the context, and any applied forces that are influencing the car's motion, such as a pushing force. It's important to represent all of these forces as vectors starting from a single point, which simplifies the car to a particle. You should not include the net force as this is determined by the vector sum of all the individual forces. In the context of the free-body diagram, the gravity and normal force are typically shown vertically, with gravity pointing downward and the normal force upward, while friction and applied forces are shown horizontally in their respective directions of action.