Back in school years, in the seventh or eighth grade, every person gets acquainted with a new concept of dynamic physics - friction. However, many, having matured, forget what friction is and how this force acts. Let's try to understand this topic.
Definition of a concept
Friction is a phenomenon that contains the following meaning: when two bodies come into contact with each other, a special interaction forms at the place of their contact, preventing the bodies from continuing to move relative to each other. It is clear that the value of the interaction of these bodies can be calculated. The friction force precisely 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 this interaction is called dry friction.
It should be understood that friction is a force of electromagnetic nature. This means that the cause of this force is the interaction between the particles of which this or that body consists.
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 has individual properties. This means that the interaction between different objects will be different. For a correct understanding of the essence and competent solution of many problems in physics, it is customary to conditionally separate three types of friction. So, we will analyze each separately:
- The first friction is the rest friction, which occurs in the absence of relative movement of two bodies. We can observe his examples everywhere, because the force arising from this friction keeps things in balance. For example, goods on a moving conveyor belt, a nail driven into a wall, or a person standing on the floor.
- Sliding friction is conditionally the second friction. The value of sliding is determined in this way: when a force is applied to a body that is in equilibrium, which is greater than the rest friction force, the sliding friction force begins to act, and the body moves.
- And finally, rolling friction , explaining the interaction of two bodies, one of which rolls over the surface of the other. The difference in rolling and sliding friction is explained by the fact that, with any movement, body areas shift along the length of the contact surface, and new ones are formed instead of broken intermolecular bonds. And in the case when the wheel rolls without slipping, the molecular bonds break when lifting sections of the wheel 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 basic things: walk, sit or just hold objects in our hands. Therefore, do not underestimate the importance of friction. As the French physicist Guillaume said: “If there were no friction, our Earth would be without a single roughness, it would be like a liquid drop.”
Perhaps the best example that most accurately describes friction is wheel performance. Even in antiquity, it was noticed that the rolling friction forces are much less than the sliding friction forces. It is the undeniable benefits of rolling friction that caused people to put logs or rollers to move heavy and bulky loads. Over time, people improved their knowledge of the amazing properties of rolling friction, observed the movement of objects under the influence of friction, and finally invented the wheel! In the modern world it is impossible to imagine life without these irreplaceable details, because wheels are the second "engines" of any transport!
How to calculate the value of the friction force?
Like any other force, the force of friction has integer values. In order to accurately determine how much force is required to move or other types of work, it is necessary to calculate the force of rest friction. Engineers usually do this when, for example, they build factories or invent new devices. However, even ordinary schoolchildren are faced with certain tasks where it is necessary to calculate the friction force. So, to calculate its value, you just need to use the simple formula: Friction F = K * N, where k is the coefficient of friction. The value of all coefficients always depends on the surface of the object along which the body moves or interacts with. "N" in our formula means the strength of the reaction of support on the body. It depends primarily on body weight, which is in contact with the surface of the support.
We calculate the value of force in the problem
Suppose a body weighing m = 3 kg is on a horizontal board. The coefficient of friction between the wooden board and the body is 0.3. How to find the value of the friction force? Very simple, all you need to do is substitute our values in the formula. It is only necessary to take into account that N in this case is equal to body weight (according to Newton’s 3rd law). So, the required force is (m * g) * k = (3 kg * 10 m / s 2 ) * 0.3 = 9 H.