Friction is the force that opposes the movement of an object. To stop a moving object, the force must act in the opposite direction to the direction of motion. For example, if you push a ball lying on the floor, it will move. The force of the push moves it to another place. Gradually the ball slows down and stops moving. The force that opposes the movement of an object is called friction. In nature and in technology, there are a huge number of examples of the application of this force.

## Types of friction

There are different types of friction:

### A skate blade moving across ice is an example of slipping. As the skater moves around the rink, the bottom of the skates touch the floor. The source of friction is the contact between the blade surface and the ice. The weight of an object and the type of surface it is moving on determinesthe amount of slip (friction) between two objects. A heavy object exerts more pressure on the surface it slides over, so there will be more sliding friction. Since friction is due to attractive forces between the surfaces of objects, the amount of friction depends on the materials of the two interacting objects. Try skating on a smooth lake and you'll find it much easier than skating on a rough gravel road

• Resting friction (cohesion) is the force that occurs between 2 contacting bodies and prevents the occurrence of movement. For example, to move a closet, hammer a nail, or tie shoelaces, you need to overcome the force of adhesion. There are many similar examples of friction in nature and technology.
• When you ride a bike, the contact between the wheel and the road is an example of rolling friction. When an object rolls on a surface, the force required to overcome rolling friction is much less than that required to overcome sliding.

## Kinetic friction

When you pushed the book on the table and it moved a certain distance, it experienced friction acting on moving objects. This force is known as the kinetic friction force. It acts on one surface of another when two surfaces rub against each other because one or both surfaces are moving. If you put additional books on top of the first book to increase the normal force, the kinetic friction force will beincrease.

There is the following formula: Ffriction=ΜFn.The force of kinetic friction is equal to the product of the coefficient of kinetic friction and the normal force. There is a linear relationship between these two forces. The coefficient of kinetic friction relates the frictional force to the normal force. Since it is a force, the unit for measuring it is Newton.

## Static friction

Imagine you are trying to push a sofa across the floor. You press it with a little force, but it doesn't move. The static friction force acts in response to force, in an attempt to cause movement of a stationary object. If there is no such force on the object, the static friction force is zero. If there is a force trying to cause movement, then the second one will increase to its maximum value before it is overcome, and movement will begin.

Formula for this view: Ffriction=ΜsFn. The static friction force is less than or equal to the product of the static friction coefficient Μ (s) and the normal force F (n). In the sofa example, the maximum static friction force balances the force of the person pushing it until the sofa begins to move.

## Measuring friction coefficients

What determines the force of friction? In nature and technology, the materials from which surfaces are made play a certain role. For example, imagine trying to play basketball while wearing socks instead of athletic shoes. It maysignificantly worsen your chances of winning. The shoe helps provide the power needed to brake and change directions quickly while running on the surface. There is more friction between your shoes and a basketball court than between your socks and a polished wood floor.

Various coefficients show how easily one object can slide over another. Their exact measurements are quite sensitive to surface conditions and are determined experimentally. Wet surfaces behave very differently than dry surfaces.

## Physics: the force of friction in nature and technology

You experience friction all the time and you should be glad it's possible. It is this force that helps to keep stationary objects in place, and a person does not fall when walking. What is friction? In nature and technology, examples can be found at every step. You may not realize it, but you are already very familiar with this power. It occurs in the opposite direction of movement, and because of this, it is a force that affects the movement of objects.

When you move the box across the floor, the friction works against the box in the opposite direction of the box. As you walk down a mountain, friction works against your downward movement. When you apply the brakes in a car and keep moving for a while, the friction works against your direction of sliding, which helps eventually stop the slip completely.

When two objects "rub" into each other, forces are setattraction between the molecules of objects, causing friction. In nature and technology, it can occur between almost any phases of matter - solids, liquids and gases. Friction occurs between two objects, such as a box and a floor, but can also occur between fish and the water in which they swim, and objects falling in the air. Friction due to air has a special name: air resistance.

## The role of friction in nature, technology, life

Friction is an integral part of the human experience. We need traction to walk, stand, work and ride. At the same time, we need energy to overcome resistance to movement, so too much friction requires excess energy to do work, resulting in inefficiency. In the 21st century, humanity is facing the twin challenges of energy shortages and global warming from burning fossil fuels. Thus, the ability to control friction has become a top priority in today's world. However, many still lack understanding of the fundamental nature of friction.

Friction in nature and technology (physics) has always been a subject of curiosity. Intensive study of the origin of this force began in the 16th century, following the pioneering work of Leonardo da Vinci. However, progress in understanding its nature has been slow, hampered by the lack of an instrument for accurate measurement. The ingenious experiments carried out by the scientist Coulomb and others have provided important information to lay the foundation for understanding. Beginning in the late 1800s and earlySteam engines, locomotives, and then airplanes appeared in the 1900s. Also, space exploration requires a clear understanding of friction and the ability to control it.

Significant progress in how to apply and control friction in nature technology, in everyday life, has been made through trial and error. At the beginning of the 21st century, a new dimension of nano-scale friction emerged due to the use of nano-technologies. Human understanding of atomic and molecular friction is expanding rapidly. Today, energy efficiency and renewable energy production require immediate attention as science strives to reduce carbon emissions. The ability to control friction becomes an important step in the search for sustainable technologies. That is the indicator of energy efficiency. If it is possible to reduce unnecessary energy losses and increase current energy efficiency, this will give time to develop alternative energy sources.

## Examples of friction in life

Friction is a force that is resistive. It impedes the movement of another object by applying some force. But where does this power come from? First, it is worth starting to consider it from the molecular level. The friction we see in everyday life can be caused by surface roughness. This is what scientists believed for a long time to be the main reason for its appearance.

The simplest examples of friction in nature and technology are the following:

• When walking, the friction force thataffects the sole, gives us the opportunity to move forward.
• A ladder leaning against a wall does not fall to the floor.
• People tying their shoelaces.
• Without the force of friction, cars would not be able to drive not only uphill, but also on a flat road.
• In nature, it helps animals climb trees.

There are many such points, there are also cases where this force, on the contrary, can interfere. For example, to reduce friction, fish are given a special lubricant, thanks to which, as well as the streamlined body shape, they can move smoothly in the water.