The friction It is the force that opposes the sliding movement produced by the contact between two surfaces. The only way for the friction force to completely disappear would be with bodies with ideally smooth surfaces, which is impossible: this is why it can be said that the friction force occurs in all known media, whether they are solid or liquid. or gaseous.
If the normal force is the one exerted when a body is supported on a surface, perpendicularly and outward, the static friction It is a force proportional to the normal, at the rate of a value called the coefficient of friction.
The formula then is F = Ц * N, where f is the force of friction or friction, Ц is the coefficient of friction and N is the normal force. This, however, is restricted to the case of static friction, where the phenomenon occurs below the movement threshold. When that threshold is exceeded, the object begins to slide on the surface and then the friction becomes less, becoming known as dynamic friction.
In daily life, the concept of friction is directly related to rubbing, scrubbing or rubbing something: the friction force is what makes the opposition, and it is what allows people or automated bodies that the human being created to stop once started .
The friction force is present to the extent that when it comes to move a heavy object horizontally, at the beginning the force that must be exerted to bring it out of rest is much greater than that which must be done once it is started, where it is much easier to put it in motion. This happens because once the static friction is overcome, the microscopic joints that held the surfaces in contact together break.
Finally, it is common for industries focused on the production of certain goods to manipulate the friction force, tending to optimize it by increasing or reducing it as the case may be: there are times when it is necessary for the surface in contact with the ground to be rough, in such a way as to increase this force. Others, on the other hand, are supported on another surface that sees friction reduction necessary, for which tools such as grease or oil are usually used, as lubricants to reduce friction between components and the energy losses they carry.
Examples of friction
Some examples of friction in everyday life, explaining the cases in which this force is manipulated with a particular function.
- The wheels of a car that roll on the pavement, intentionally high to give the driver more control over the vehicle.
- The design of all kinds of vehicles, be they submarines, boats and all those that move on the water.
- The friction between an airplane and the air, when it is flying. This friction is dependent on the aerodynamic design.
- An object perched on the ground, which is very difficult to give the initial impulse but somewhat easier to move once that impulse has been produced.
- Sliding a body on a wet plastic, which gives it more travel than on dry plastic, precisely because water reduces the friction force between surfaces.
- A match when it collides with the box, generating the combustion necessary to ignite.
- Rubbing between two objects such as stones or wood, which generate heat and eventually fire.
- An ice skating rink, where friction is reduced and therefore skates are used so that the displacement is greater.
- The sole of the shoes, with special engravings to increase friction.
- The rub between the two hands, or any part of the body.