Aerodynamics deals with the study of the movement of air and the effects it has on objects moving through air and plays a crucial part in determining the performance, stability and mileage of a racing car. Car bodies are streamlined or designed in a way that it uses airflow to increase its traction and decrease the resistance offered by air.
We shall look at the factors which determine the shape of car bodies.
We are going to understand the Essence of Race Car Aerodynamics broadly through three topics.
2. Newton’s Third Law of Motion
3. Forces exerted by Air Flow
Air consists of tiny molecules flying around in the volume it occupies. In an intuitive sense, we can say pressure is the busyness of the air molecules. The air molecules collide with each other and with the objects present in the volume of air. This rate of collision increases if we increase the air density, or raise the temperature.
When we fill a balloon with air, the molecules in the air collide with the surface of the balloon, thus exerting a force and keeping the balloon inflated. Notice that the air outside doesn’t push the balloon to its normal shape even though two forces, external air pressure and elastic force exerted by the surface of the balloon are acting to restore the balloon’s normal shape. Therefore, we conclude that the air inside the balloon exerts more pressure than the air pressure outside the balloon.
However, if we open the mouth of the balloon the air rushes out quickly. This is because the force of the air molecules exiting the balloon is stronger than the force of air molecules trying to enter the balloon. Therefore, we conclude that air flows from a region of high pressure to a region of low pressure. Not only that, but you might have observed that the air flows out really fast from the balloon. This is because the opening of the balloon is small and in order for the mass flowing through all cross-sections to be constant, the velocity of the air in a smaller cross-section must be greater, commonly known as Continuity Equation. Thus, our second conclusion is air flows faster when it is forced to flow from a region of greater volume to a region of smaller volume. Note that in a balloon this effect is greater because of elastic force acting to push out the air.
NEWTON’S THIRD LAW OF MOTION
This law states that every action has an equal and opposite reaction. It means if you push against something, it pushes you back with equal amount of force. When a bird flaps its wings against the wind to push it, the air pushes the bird back and the bird stays afloat. Thus, when we want to move in a particular direction, we need to push the air in the opposite direction.
FORCES EXERTED BY AIR FLOW