‘Force of Friction’ is the force exerted by any surface when an object moves across it. Friction goes against the overall movement between two surfaces in touch. It acts on both surfaces. The resistance to motion of one object moving relative to another is defined as friction. It is not a fundamental force in the same way that gravity or electromagnetism are. Scientists believe it is caused by the electromagnetic attraction of charged particles on two surfaces that are in contact.

Scientists began piecing together the laws governing friction in the 1400s, but because the interactions are so complex, characterizing the force of friction in various situations typically requires experiments and cannot be derived solely from equations or laws.

There are as many exceptions to every general rule about friction. For example, while two rough surfaces (such as sandpaper) rubbing against each other may have more friction, very smoothly polished materials (such as glass plates) that have been thoroughly cleaned of all surface contaminants have less friction,  particles may actually stick to each other very strongly.

Factors affecting Friction:

• Friction is brought about by the irregularities on the two surfaces in touch
• Even those surfaces which are smooth have numerous minute irregularities on them
• On harsh surfaces, there are a bigger number of irregularities
• Thus, the power of friction is more if a harsh surface is involved

• Irregularities between the two levels create friction
• Clearly, the power of friction will increase if the two surfaces are pressed harder

Types of Friction:

Following are the main types of friction:

Static Friction: Static friction becomes an important factor when we attempt to move an object at rest. 

Sliding Friction: Sliding friction becomes the most important factor when an object is sliding over another. 

Rolling Friction: When one body turns over another body, rolling friction becomes an important factor.

Fluid Friction: Fluids (gases and liquids) exert the force of friction on objects in motion through them. The frictional force applied by fluids is also called drag. 

In the case of solid surfaces, three types of friction occur sliding, static and rolling. 

Fluid friction takes place in fluids.

Fluid friction:

Fluid friction is a force that restricts the movement of a liquid or another medium moving through it. Internal friction occurs as a result of the movement of the molecules within the fluid, and external conflict occurs as a result of how the fluid interacts with other matter. It describes the friction that occurs between the moving layers of a viscous liquid. Viscosity is the term used to describe the internal resistance to flow. The greater the ease of movement or frictional force, the less dense the fluid. Fluid friction is commonly used in water slides to gently prompt or slide down.

 In the case of sliding friction and static friction, sliding friction is comparatively less than static friction.

 Rolling friction is less than sliding friction.

Friction: A Necessary Evil

Friction is important for many activities such as stopping vehicles. On the other hand, friction is also evil:

• It destroys the materials whether they are screws, metal rollers or soles of shoes
• Friction produces heat
• In machine operation, heat generated causes wastage of energy

Increasing and Reducing Friction:

Friction is desirable in many cases and thus increased by making a surface rough. For example, under shoes and car tires are treated to increase friction.

In some situations, friction is undesirable and can be minimized in the following ways:

• Use of Lubricants: The substances which reduce friction are called lubricants such as oil, and grease
• In certain machines, the oil may not be used as a lubricant
• An air pad between the moving parts is used to retard friction
• Wheels Reduce Friction: Because rolling friction is less than sliding friction, the use of metal bearings replaces sliding in many machines
• Examples are the utilization of metal bearings among centre points and the axles of roof fans and bicycles

Combatting Fluid Friction:

Fluid friction relies upon the speed of the object concerning the liquid, the state of the object and the nature of the fluid. When objects move through fluids, they must overcome friction acting on them to avoid loss of energy and increase efficiency.

• Objects are given unique shapes to limit friction
• Inspirations from nature are incorporated in designs such as the shape of an aeroplane is like birds

Conclusion:

Friction is essential in many everyday processes. When two objects rub together, for example, some of the energy of motion is converted into heat. This is why rubbing two sticks together will eventually result in the formation of a fire.

Friction is also to blame for the wear and tear on bicycle gears and other mechanical components. As a result, lubricants, or liquids, are frequently used to reduce friction and thus wear and tear between moving parts.