A car is skidding to a stop on a level stretch of road. Identify the number of the action/reaction pairs of forces between the car and the road surface.

This question can be answered via the Newton's Third law of Motion which states that, "For every action, there's an equal and opposite reaction". Hence the forces/reaction between the car and the road are:

1) Car's weight on the road and force from the road to the car.

2) Friction of the car tyres on the road surface and friction from the road surface on the car tyres.

The pairs of action/reaction forces are as follows:

1. The friction force that the car exerts on the road and vice versa, the friction force that the road exerts on the car.

2. The normal force exerted by the road on the car and vice versa, the normal force exerted by the car on the road.

Explanation:

According to the question, the weight of the car acts downward and the normal force acting on the car exerts upward. When the car begins to skate on the road, the friction force of the road on the car is balanced with the friction force that the car exerts on the road.