The Net Force on Car Tires: Understanding the Driving Force on a Level Road


When a car accelerates along a level road, several forces come into play to propel it forward. Among these forces, the net force on the tires plays a crucial role in determining the car’s acceleration and overall motion. In this article, we will delve into the concept of net force and explore the various factors that contribute to the driving force exerted on the tires of a car.

Net force, also known as the resultant force, refers to the overall force acting on an object after considering all the individual forces acting upon it. In the case of a car moving along a level road, the net force on the tires is the combined effect of several forces, such as propulsion, friction, air resistance, and the normal force exerted by the road surface.

The primary force responsible for accelerating a car is the propulsion force generated by the car’s engine. This force is transmitted to the wheels through the drivetrain and ultimately applied to the tires. The propulsion force is directed forward, pushing the tires against the road surface and causing the car to move.

Friction is another important force that affects the net force on car tires. As the tires rotate, they experience rolling friction with the road surface. This frictional force acts in the opposite direction to the car’s motion, resisting its movement. However, the friction between the tires and the road also provides the necessary grip for the tires to propel the car forward.

Air resistance, also known as drag, is a force that opposes the motion of a car through the air. As the car moves, it encounters resistance from the air molecules, creating a drag force. This force acts opposite to the car’s direction of motion and can have a significant impact on the net force exerted on the tires. Higher speeds generally result in greater air resistance.

The normal force is the perpendicular force exerted by the road surface on the tires of a car. It counteracts the force of gravity and supports the weight of the car. The normal force plays a crucial role in determining the tire’s grip on the road. It enables the tires to generate sufficient friction and maintain traction, allowing the propulsion force to be effectively transmitted to the road.

Although weight is not directly related to the net force on the tires, it is an essential factor that influences the normal force. The weight of the car is the force exerted on it due to gravity. The normal force balances the weight, ensuring that the tires have sufficient contact with the road surface to generate the required friction and propel the car forward.

External Forces In addition to the forces mentioned above, there may be other external forces that impact the net force on the tires. For example, if the car encounters an inclined road, the gravitational force component along the incline may affect the net force. Other external factors, such as crosswinds or uneven road surfaces, can also influence the net force acting on the tires.


The net force on the tires of a car moving along a level road is a result of various forces, including propulsion, friction, air resistance, and the normal force exerted by the road. Understanding these forces and their interactions provides valuable insights into the mechanics of a car’s motion and helps optimize its performance on the road.