If a car moves at a constant speed on a certain horizontally rectilinear section of the road, then it can be argued that …

According to 1 Newton’s law, a body can be in a state of rest or uniform rectilinear motion if no forces act on it or the action of forces is compensated.

Since the car moves along a straight section of the road at a constant speed, the forces acting on it are compensated. The force of gravity m * g is compensated by the reaction force of the road N, the thrust force of the engine Ftr is compensated by the force of resistance to motion Fcopr.

When the car is moving, the resultant of all the forces applied to the car is zero.