Even in school years, in the seventh or eighthclass, each person gets acquainted with the new concept of dynamic physics - friction. However, many, having grown up, forget what friction is and how this force works. Let's try to understand this topic.
Definition of concept
Friction is a phenomenon that includesthe 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. It is clear that the value of the interaction of these bodies can be calculated. 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 this interaction is called dry friction.
It should be understood that friction is a force that haselectromagnetic 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?
Thanks to the diversity of existing in our worldobjects 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 correctly understand the essence and the competent solution of many problems in physics, it is conventionally divided into three types of friction. So, we will analyze each separately:
- First friction This is the quiescent friction that occurs whenabsence of relative displacement of two bodies. We can observe its examples everywhere, because the force arising from 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.
- Sliding friction this 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, explaining the interaction of two bodies, one ofwhich rolls over the surface of the other. The difference in friction between rolling and sliding is explained by the fact that, for any movement, the areas of the body are displaced 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 frictional force of rolling is less than the sliding force.
Where and how can you use friction?
Friction is an indispensable phenomenon, without which wewould not be able to do elementary things: walk, sit or just keep 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 that is most accuratecharacterizes friction, is the wheel's work. In antiquity it was noticed that the frictional forces of rolling are much less than the sliding friction forces. It is the unquestionable 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 possessesinteger 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, they build plants or invent new devices. However, even ordinary school children 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: Ffriction = 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.
We calculate the value of the force in the problem
Suppose a body of mass m = 3 kg is onhorizontal board. The coefficient of friction between the wooden board and the body is 0.3. How to find the value of the force of friction? 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 / s2) * 0.3 = 9 H.
