Final answer:
The forces acting on a car moving at constant speed are equal and opposite, resulting in a net force of zero according to Newton's first law. Therefore, the answer is (b) The forces are equal in size, act in opposite directions, and produce a zero net force.
Step-by-step explanation:
When analyzing the forces acting on a car in motion, different scenarios dictate the relationship between these forces. If the car is moving at a constant speed, according to Newton's first law of motion, the forces acting on the car are equal in size and oppose each other, resulting in a net force of zero. This means that the frictional force is equal to the drag or applied force, and the car continues to move at a steady pace without accelerating. On the other hand, if the car is accelerating, it indicates that there is an imbalance of forces, where the net force acting on the car is in the direction of the acceleration. Therefore, the correct answer to the question is option (b) The forces are equal in size, act in opposite directions, and produce a zero net force, when the car moves at a constant velocity.