* Constant velocity means zero acceleration. This is a key point! Newton's first law tells us that an object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction *unless acted upon by an unbalanced force*.

* Equilibrium means no net force. For an object to be in equilibrium, all the forces acting on it must balance out.

Therefore, the additional force needed to bring the car into equilibrium is zero. The car is already in equilibrium because it's moving at a constant velocity.

Let's think about the forces acting on the car:

* Forward force: This is the force from the engine that propels the car forward.

* Friction: This is the force opposing the car's motion (air resistance, friction from the tires on the road, etc.).

* Other forces: Gravity and the normal force from the road are also present, but since the car is on level ground, these forces cancel each other out vertically.

Since the car is moving at a constant velocity, the forward force and the friction force must be equal and opposite, resulting in a net force of zero. No additional force is needed to achieve equilibrium.