Even during school years, in the seventh or eighth grade, each person gets acquainted with a new concept of dynamic physics - friction. However, many, having matured, forget what friction is and how this force works. 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 each other, a special interaction is formed at the place of their contact, preventing the bodies from continuing to move relative to each other. It is clear that it is possible to calculate the value of the interaction of these bodies. The force of friction characterizes this interaction quantitatively. If friction occurs between rigid bodies (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 that has an electromagnetic nature. This means that the cause of this force is the interaction between the particles that make up this or that body.
What is friction?
Due to the variety of items that exist in our world, you candetermine that each of them has its own structure and has individual properties. This means that the interaction between different items 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, let's analyze each one separately:
- The first friction is the static friction that occurs when there is no relative movement of two bodies. We can see examples of him everywhere, because the force generated by this friction keeps objects 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 defined as follows: when a force is applied to a body in equilibrium that is greater than the static friction force, the sliding friction force begins to act, and the body moves.
- And finally, rolling friction, which explains 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, the areas of the body are displaced along the length of the contact surface, and instead of broken intermolecular bonds, new ones are formed. And in the case when the wheel rolls without slipping, the molecular bonds break much faster when the wheel sections are lifted 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 isan irreplaceable phenomenon, without which we would not be able to do elementary things: walk, sit, or simply 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 characterizes friction is the operation of a wheel. Even in antiquity, it was noticed that the forces of rolling friction are much less than the forces of sliding friction. It was 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 forces, and finally invented the wheel! In the modern world, it is impossible to imagine life without these irreplaceable parts, because wheels are the second "engines" of any transport!
How to calculate the value of the friction force?
Like any other force, the friction force has integer values. In order to accurately determine how much force is required for movement or other types of work, it is necessary to calculate the static friction force. 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 required to calculate the friction force. So to count itvalue, you just need to use a simple formula: Ffriction=KN, where k is the coefficient of friction. The value of all coefficients always depends on the surface of the object on which the body moves or interacts. "N" in our formula means the reaction force of the support on the body. It depends primarily on the mass of the body that is in contact with the surface of the support.
Calculate the value of the force in the problem
Assume a body of mass 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? It's very simple, all you need to do is plug our values into the formula. You just 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 desired force is (mg)k=(3 kg10 m/s2)0, 3=9 H.
