Friction is one of the most important concepts of dynamics. What do you know about it?

Even in school years, in the seventh or eighth grade, each person gets acquainted with the new concept of dynamic physics - friction. However many, having grown up, forget, that such friction and in what way this force operates. Let's try to understand this topic.

Definition of concept

Friction is a phenomenon that has the following meaning: when two bodies come into contact with one another, a special interaction is formed at the place of their contact, preventing the bodies from continuing to move relative to each other. Clearly, it is possible to calculate the significance of the interaction of these bodies. The frictional force is precisely what characterizes this interaction quantitatively. If friction occurs between solids (for example, the interaction of a book with a bookshelf or an apple with a table), then such an interaction is called dry friction.

It should be understood that friction is a force that is electromagnetic in nature. This means that the cause of this force is the interaction between the particles of which this or that body is made up.

What is friction?

Due to the variety of objects existing in our world, it can be determined that each of them has its own structure and possesses individual properties. This means that the interaction between different objects will be different. To properly understand the essence and competent solution of many problems in physics, it is conventionally divided into three types of friction. So, we will analyze each separately:

• The first friction is the friction of rest, which occurs when there is no relative displacement of two bodies. We can observe its examples everywhere, because the force that occurs with this friction keeps objects in balance. For example, goods on a moving conveyor belt, a nail driven into the wall or a person standing on the floor.
• Slip friction is conditionally second friction. The glide value is determined in this way: when a force is applied to the body in equilibrium, which is greater than the friction force of rest, the sliding friction force starts to act, and the body shifts from its place.
• Finally, rolling friction , which explains the interaction of two bodies, one of which rolls over the surface of the other. The difference in friction between rolling and sliding is explained by the fact that, for any motion, the areas of the body move along the length of the contact surface, and instead of the broken intermolecular bonds, new ones are formed. And in the case when the wheel rolls without slippage, the molecular bonds at the lifting of the parts of the wheel break much faster than when sliding. It turns out that the rolling friction force is less than the sliding force.

Where and how can friction be used?

Friction is an indispensable phenomenon, without which we would not be able to do elementary things: walking, sitting, or just keeping things in hand. Therefore, do not underestimate the importance of friction. As the French physicist Guillaume said: "Do not be friction, our Earth would be without a single roughness, it would be like a liquid drop."

Perhaps the best example, which most accurately characterizes friction, is the wheel's work. Even in antiquity it was noted that the frictional forces of rolling are much less than the sliding friction forces. It is the undeniable benefit of rolling friction that has caused people to put logs or rollers to move heavy and oversized loads. Over time, people improved their knowledge of the amazing properties of rolling friction, watched the movement of objects under the influence of frictional forces and, finally, invented the wheel! In the modern world it is impossible to imagine life without these irreplaceable details, because the wheels are the second "engines" of any transport!

How to calculate the value of the frictional force?

Like any other force, the frictional force has integer values. In order to determine exactly how much force is required for displacement or other types of work, it is necessary to calculate the friction force of rest. This is usually done by engineers, when, for example, plants are built or new devices are invented. However, even ordinary schoolchildren face certain tasks, where it is required to calculate the force of friction. So, to calculate its value, you just need to use an uncomplicated formula: F _friction = K * N, where k is the coefficient of friction. The value of all the coefficients depends always on the surface of the object, on which the body moves or interacts. "N" in our formula means the strength of the reaction of support on the body. It depends primarily on the mass of the body, which is in contact with the surface of the support.

Calculate the value of the force in the problem

Suppose a body weighing m = 3 kg is on a horizontal board. The friction coefficient between the wooden board and the body is 0.3. How can we find the value of the frictional force? It's very simple, just need to substitute our values in the formula. Only need to take into account that N in this case is equal to the weight of the body (according to Newton's 3rd law). So, the required force is (m * g) * k = (3 kg * 10 m / s ² ) * 0.3 = 9 H.