We are so used to being surrounded by air that we often do not pay attention to it. We are talking here, first of all, about applied technical problems, in solving which at first it is forgotten that there is an air resistance force.
She reminds herself in almost any action. Even if we go by car, even fly by plane, even if we just throw a stone. So let's try to understand what constitutes the force of air resistance on the example of simple cases.
Have you ever wondered why cars have such a streamlined shape and flat surface? But everything is actually very clear. The force of air resistance consists of two quantities - from the resistance to friction of the surface of the body and the resistance to body shape. In order to reduce the frictional force, they also seek to reduce roughnesses and roughnesses on external parts in the manufacture of automobiles and any other vehicles.
To do this, they are primed, stained, polished and varnished. Such processing of parts leads to the fact that the air resistance acting on the car decreases, the speed of the car increases, and fuel consumption during movement decreases. The presence of the resistance force is explained by the fact that when the car moves, the air is compressed and a region of local increased pressure is created in front of it, and after it, accordingly, the region of rarefaction.
It should be noted that at elevated speeds of the car, the shape of the car makes the main contribution to the resistance. The resistance force, the calculation formula of which is given below, determines the factors on which it depends.
Resistance force = Cx * S * V2 * r / 2
where S is the area of the front projection of the machine;
Cx - coefficient taking into account aerodynamic drag ;
V is the speed of movement;
r is the density of air.
As you can easily see from the above formula, the resistance force does not depend on the mass of the car. The main contribution is made by two components - the square of speed and the shape of the car. Those. with an increase in the speed of movement two times four times the resistance will increase. Well, the cross-section of the car has a significant impact. The more streamlined the car, the less air resistance.
And in the formula there is also a parameter that simply requires close attention to it - air density. But its influence is already more noticeable when flying aircraft. As you know, with increasing height, air density decreases. This means that the strength of its resistance will decrease accordingly. However, for an airplane, the same factors — speed and shape — will continue to influence the amount of resistance provided.
No less interesting is the history of the study of the effect of air on accuracy. Works of a similar nature have been conducted for a long time, their first descriptions date back to 1742. The experiments were carried out in different countries, with different shapes of bullets and shells. As a result of the research, the optimal shape of the bullet and the ratio of its head and tail were determined, ballistic tables of the behavior of the bullet in flight were developed.
Further studies were conducted on the dependence of the flight of the bullet on its speed, the shape of the bullet continued to be worked out, and the research methodology was improved . Mathematical models were developed and a special mathematical tool was created - a ballistic coefficient. It shows the ratio of aerodynamic drag forces and inertia forces acting on a bullet.
The article considers what constitutes the force of air resistance, gives a formula that allows you to determine the magnitude and degree of influence of various factors on the magnitude of the resistance, its effect in different areas of technology is considered.