Friction

Friction is a force that we encounter in our everyday lives. It plays a crucial role in various aspects, from walking to driving a car. However, there are certain situations where friction is not useful and can even be a hindrance. In this article, we will explore these scenarios and understand why friction may not always be beneficial. We will delve into areas such as lubrication, transportation, and technology to uncover where friction can pose challenges and limitations. So, let’s dive in and discover where friction falls short in its usefulness.

Key Takeaways

• Friction is not useful in situations where smooth and efficient movement is required, such as in the design of machinery and vehicles.
• Friction can hinder the performance of moving parts and cause wear and tear, leading to decreased efficiency and increased maintenance.
• In certain sports and activities, minimizing friction can enhance performance and reduce the risk of injury.
• Lubricants and other methods can be used to reduce friction and improve the overall efficiency of mechanical systems.

Where is Friction Not Useful?

Friction is a force that resists the relative motion or tendency of motion between two objects in contact. While friction plays a crucial role in many aspects of our daily lives, there are certain situations where it is not useful or even detrimental. Let’s explore some of these scenarios.

In Sports

In the world of sports, friction can sometimes hinder performance. For example, in track and field events such as sprinting, athletes strive to minimize friction between their shoes and the ground. This is why sprinters wear specialized shoes with spikes that provide better traction. By reducing friction, sprinters can maximize their speed and efficiency, allowing them to achieve faster times.

For Skateboarders

Skateboarding is another area where friction can be a hindrance. Skateboarders often perform tricks and maneuvers that require smooth and controlled movements. Excessive friction between the skateboard wheels and the ground can impede these movements, making it difficult to execute tricks with precision. To overcome this, skateboarders often apply wax or other lubricants to reduce friction and ensure smoother rides.

In Airplanes

Friction also poses challenges in the aviation industry. When an airplane is in flight, it encounters air resistance, which is a form of friction. This resistance opposes the motion of the aircraft and requires additional energy to overcome. To minimize this drag, airplanes are designed with streamlined shapes and smooth surfaces. By reducing friction with the air, airplanes can achieve greater fuel efficiency and higher speeds.

Where There is No Friction

In certain situations, having no friction can be advantageous. For example, in manufacturing processes that involve moving heavy objects, friction can make it difficult to slide or transport them. By utilizing frictionless materials or lubricants, the objects can be moved with ease, reducing the effort required and increasing efficiency.

Where Friction is Not Helpful

Friction can also be a disadvantage in certain mechanical systems. For instance, in engines and machines, friction between moving parts can lead to wear and tear, reducing their lifespan and efficiency. To mitigate this, engineers employ various techniques such as using lubricants, bearings, and precision engineering to minimize friction and ensure smooth operation.

In Swimming

When it comes to swimming, friction can slow down swimmers and impede their progress through the water. Competitive swimmers wear specialized swimsuits that are designed to reduce drag and minimize friction with the water. These swimsuits are made from materials that repel water and have a smooth surface, allowing swimmers to glide through the water with minimal resistance.

In Everyday Life

Friction can sometimes be a nuisance in our everyday lives. For example, squeaky doors and hinges are often a result of friction between the moving parts. To address this, lubricants such as oil or grease are applied to reduce friction and eliminate the annoying noise. Similarly, when sliding furniture across the floor, friction can make it challenging to move them smoothly. Using furniture sliders or applying a lubricant can help reduce friction and make the process easier.

Where Friction is Used in Everyday Life

While friction can be problematic in certain situations, it is also essential in various aspects of our daily lives. For instance, the soles of our shoes have a tread pattern that increases friction with the ground, providing us with traction and preventing slips and falls. Additionally, the brakes in vehicles rely on friction to slow down and stop the moving wheels, ensuring our safety on the roads.

In conclusion, while friction is a fundamental force that has numerous benefits, there are specific scenarios where it is not useful or even detrimental. Whether it’s in sports, aviation, or everyday life, understanding when and where friction can be a disadvantage allows us to find innovative solutions to overcome its limitations and improve our efficiency and performance.

Interesting Facts about Friction

Friction is a force that we encounter in our daily lives, often without even realizing it. It plays a crucial role in various aspects of our lives, from walking to driving a car. Let’s explore some intriguing facts related to friction.

Friction is Everywhere

Friction is present in almost every interaction between objects. Whether it’s the grip between your shoes and the ground, the movement of gears in a machine, or the rubbing of your hands together, friction is at work. It is a force that opposes motion and is caused by the roughness of surfaces.

Friction Can Be Both Helpful and Harmful

While friction is essential for many everyday activities, there are instances where it can be a disadvantage. For example, in machines and engines, friction between moving parts can cause wear and tear, leading to decreased efficiency and increased energy consumption. To overcome this, engineers strive to reduce friction by using lubricants and designing smoother surfaces.

Friction Generates Heat

When two surfaces rub against each other, the friction between them generates heat. This phenomenon can be observed when you rub your hands together vigorously and feel them getting warmer. In some cases, excessive heat due to friction can cause damage or even start a fire. That’s why it’s important to be cautious and avoid situations where friction can lead to overheating.

Friction Can Be Reduced

In certain situations, reducing friction is desirable. For example, in sports, athletes often wear special shoes with low friction soles to minimize resistance and improve performance. Similarly, in industries, engineers design machines and equipment with friction-reducing mechanisms to increase efficiency and reduce energy consumption.

Friction Can Be Overcome

In some cases, friction can be a significant obstacle that needs to be overcome. For instance, when launching a rocket into space, the force of friction between the rocket and the Earth’s atmosphere can hinder its ascent. To overcome this, rockets are designed with powerful engines that generate enough thrust to propel them through the atmosphere and into space.

Friction Affects Motion

Friction has a direct impact on the motion of objects. It can either slow down or stop the motion of an object or help to maintain its speed and direction. For example, the friction between the tires of a car and the road allows the driver to control the vehicle’s movement by applying the brakes or accelerating.

Friction Can Cause Wear and Tear

One of the disadvantages of friction is that it can cause wear and tear on surfaces. When two objects rub against each other, the friction between them can lead to the erosion of materials, resulting in the need for repairs or replacements. This is why regular maintenance and lubrication are essential to minimize the effects of friction in machines and equipment.

Friction is Essential for Walking

Friction plays a vital role in our ability to walk. When we take a step, the friction between our shoes and the ground provides the necessary grip to propel us forward. Without friction, walking would be challenging, and we would constantly slip and fall.

Friction Can Create Sound

Friction can also produce sound. When you rub your hands together, the friction between your palms generates a sound. Similarly, when you play a musical instrument, the friction between the instrument’s strings and your fingers creates vibrations that produce sound waves.

Friction is Essential for Writing

The friction between the tip of a pen or pencil and the paper is what allows us to write. As we move the writing instrument across the paper, the friction between the two surfaces creates enough resistance for the ink or graphite to leave a mark.

In conclusion, friction is a force that is present in various aspects of our lives. While it can be both helpful and harmful, understanding how friction works allows us to harness its benefits and overcome its disadvantages. From walking to writing, friction plays a crucial role in our daily activities, making it an essential force to be aware of.
Conclusion

In conclusion, friction is a fundamental force that plays a crucial role in our everyday lives. It helps us walk, drive, and perform various tasks. However, there are certain situations where friction is not useful. These include instances where we want to reduce energy loss, such as in the case of mechanical systems or transportation. Friction can also be detrimental in situations where we want to minimize wear and tear, such as in the case of machinery or moving parts. Additionally, friction can hinder the efficiency of certain processes, such as in the case of fluid flow or electrical conductivity. By understanding where friction is not useful, we can find ways to mitigate its effects and improve overall performance in various fields.

Where is friction not useful and what are some techniques to reduce friction effectively?

Friction can be both beneficial and detrimental depending on the context. While friction is essential for many everyday activities like walking or driving, it can hinder performance in certain situations. One example is in the field of engineering where friction between moving parts can lead to wear and energy loss. To address this issue, techniques to reduce friction effectively have been developed. These techniques range from lubrication and surface treatments to the use of low-friction materials. To learn more about these techniques, visit “Techniques to Reduce Friction Effectively”.

Frequently Asked Questions

When is friction not useful in sports?

Friction is not useful in sports when athletes want to achieve high speeds, such as in track and field events like sprinting or when a ball needs to travel a long distance, like in golf or baseball.

Where is friction not a good thing for a skateboarder?

Friction is not a good thing for a skateboarder when they are attempting tricks that require smooth and controlled movements, such as slides or grinds. Friction can hinder their ability to execute these tricks properly.

Why is air resistance friction not useful for an airplane?

Air resistance, which is a form of friction, is not useful for an airplane because it creates drag, which can slow down the aircraft and increase fuel consumption. To maximize efficiency, airplanes are designed to minimize air resistance.

Where is there no friction?

In a frictionless environment or on frictionless surfaces, there is no friction. These conditions can be simulated in laboratories or achieved in certain applications to study the effects of friction or reduce its impact.

Where is friction not helpful?

Friction is not helpful in situations where smooth and effortless movement is desired, such as in the design of machinery or vehicles. Excessive friction can cause wear and tear, reduce efficiency, and lead to energy losses.

Why is friction not useful in swimming?

Friction is not useful in swimming because it creates resistance against the movement of the swimmer through the water. To swim faster, swimmers try to minimize friction by wearing streamlined swimsuits and using efficient swimming techniques.

When is friction not useful in everyday life?

Friction is not useful in everyday life when it causes unwanted wear and tear, hinders movement, or reduces efficiency. For example, friction between the moving parts of a machine can lead to breakdowns or friction between shoes and the floor can make walking difficult.

Where is friction used in everyday life?

Friction is used in everyday life in various applications, such as when walking, driving a car, or using tools. It helps us maintain grip, control motion, and perform tasks that require force or traction.

What are some sports where friction is not useful?

Sports where friction is not useful include ice hockey, speed skating, and skiing. In these sports, reducing friction allows athletes to glide smoothly and achieve higher speeds.

How is friction not useful when ice skating?

Friction is not useful when ice skating because it can slow down the skater and make it difficult to perform certain maneuvers. Skaters often try to minimize friction by using smooth ice surfaces and wearing appropriate skating gear.

Why is friction not always useful?

Friction is not always useful because it can cause energy losses, wear and tear, and hinder movement. In certain situations, reducing or eliminating friction can lead to improved efficiency, performance, and longevity.

Can you provide two examples where friction is not useful?

Two examples where friction is not useful are in the design of high-speed trains and the development of low-friction bearings. In both cases, reducing friction allows for faster and more efficient transportation and machinery.

Is friction not useful in skiing?

Friction is not useful in skiing when skiers want to achieve high speeds or perform tricks. By reducing friction, skiers can glide smoothly on the snow and have better control over their movements.

Where is friction useful?

Friction is useful in various applications, such as walking, driving, and gripping objects. It helps us maintain stability, control motion, and perform tasks that require traction or force.

Also Read:

• How to find normal force with coefficient of friction
• Coulomb friction vs viscous friction
• Example of kinetic friction
• Table without friction
• Find coefficient of friction given velocity and distance
• What is wet coefficient of friction
• Difference between friction and viscosity
• Why static friction is greater than kinetic
• Wet friction
• Bad friction

In this article, we will see about one of the types of frictional force that acts on wet floors, known as wet friction.

Wet friction can be defined as the fundamental force of friction that can be seen between two surfaces of different nature (solid and liquid). It is mainly introduced to lower the intensity of friction acting between the surfaces. It exhibits less friction compared to dry friction.

Now let’s know about wet friction in detail, which is the post’s primary focus.

What is wet friction

Wet friction is almost kind similar to fluid friction but differs in some criteria.

The wet friction occurs between a rigid solid surface and loosely bound molecules of a liquid surface. It is one of the types of friction force that exhibits a lower value of friction that is determined with the help of a coefficient. We can get an idea by reading out its name.

Let us know in detail about materials that exhibit less friction.

Wet friction materials

Wet friction materials are those which, when in use, must cause low friction.

The materials that cause friction act in the fluid medium are known as wet friction. The natural material that possesses wet friction are fibers, resins, fillers, rubbers, oil, cork, paper, etc. If there is a need for continuous sliding appliances, wet friction materials are indeed beneficial.

Now let us know the coefficients of these wet friction materials.

Wet friction coefficient

The wet friction coefficient is a formula used to measure the value frictional force acting between solid and liquid surfaces.

In detail, we can say that to measure the coefficient of wet friction of certain materials, and we must first calculate the force of friction acting on individual surfaces. Then, we have to consider its ratio. It tells us the value of the opposing force needed to stop the body.

It is time to know which material exhibits more opposing force with the help of the coefficients list.

List of coefficient of wet friction in materials

Here are the coefficients of wet friction of some essential materials.

Now let us see some natural examples of wet friction.                                                      

Wet friction examples

The examples of wet friction that are mentioned below are some natural experiences that we observe daily.

• Swimming in the pool
• Coral reefs
• Movement of Honey
• Hands onto a river
• Movement of fishes in the ocean
• Sucking cold beverage through a straw
• Splashing water onto your face during a play
• Shaving cream
• Pressing toothpaste out of its tube

Swimming in the pool

A swimmer must maintain his body balance in a streamlined position to exert some force to swim forward. Here the pool water exerts some amount of force on his body to stop him. Here the wet friction acts along with the layer of his skin and surface of moisture which is significantly less. Due to this, he will be able to swim.

Coral reefs

It is known that the coral reefs present will have a slight movement which is usually due to wet friction or fluid friction. This friction will be less or high depending on the number of irregularities on the two surfaces in contact.

Movement of Honey

We know that the flow of honey will be slow due to its thick density. Here the surface of the liquid layer, i.e., honey, and on the surface on which it is spread is solid exhibits wet force of friction on each other. Since the density is thick, it requires a high wet friction force to stop the movement of honey.

Movement of fishes in the ocean

Similarly, as a swimmer’s body is streamlined, even the fishes have the same body structure, which helps them move freely in the ocean water. The wet friction force acts between the layer of fish skin and the water’s surface (Solid and liquid surface); the friction will be lesser than making the movement manageable.

Sucking cold beverage through a straw

When you drink a cold beverage with the help of a straw, you feel some difficulty to suck if the beverage is a little denser (thicker); if the liquid is thinner or less dense, you feel easy to suck it. Here wet friction plays a vital role in providing the right amount of force according to density.

Splashing water onto your face during a play

When you visit a water place, you usually start to play by splashing water on your peer group, the density of water splashed depends entirely on the force of wet friction. If the wet friction is less, there will be a minor splash, and if the wet friction is high, the splash will be increased.

Shaving cream

When you apply the shaving cream, it acts as a lubricant that reduces the wet force of friction between the blade’s surface and the face. Initially, there will be dry friction, but after applying cream, there will be wet friction that helps remove the unwanted beard through easy movement.

Pressing toothpaste out of its tube

We find two types of toothpaste: some will be thicker in density, and the other will be thinner. We require more force to suck out the thicker toothpaste from its tube than the more delicate paste. Similarly, wet friction will be less in thinner toothpaste that making the movement manageable.

After all these concepts, now let’s know about dry friction vs wet friction.

Dry friction Vs wet friction 

The essential differences between dry friction and wet friction are mentioned below,

After these differences, let us look at the critical effects of wet friction as mentioned next.

Stirbeck curve

Stirbeck curve is one of the main ideas that help in the demonstration of wet friction.

The Stirbeck curve is used in higher machines to know the efficiency and is mainly used in the concepts of tribology. It shows the relationship between objects which are lubricated with fluids, when plotted, shows a non-linear curve of the contact surface-viscosity of the lubricant and its speed.

Now let us see some main factors that affect friction.

Factors affecting wet friction

The necessary factors that affect wet friction are given below,

• The viscosity of the material.
• Temperature and the area of a surface is one of the main factors.
• Shape and nature of the material.
• Speed of the flow or movement of object under consideration.
• Pressure is the essential factor to be considered.

Now let us look into the ways of obtaining wet friction.

Ways of obtaining wet friction

There are numerous ways of obtaining wet friction. Some of them are mentioned below;

• To make the floor smoother, we have to polish it.
• To increase the coefficient of wet friction, you can make it smoother with the help of available lubricants.
• Another way is to modify the objects in a streamlined shape to make it easier for them to get along with fluid friction.
• Try to reduce the normal force when two surfaces are in contact with the help of thin liquids.
• You can also obtain wet friction y reducing the area of contact between two surfaces.

It is time to know the problems with wet friction.

Problems based on wet friction

The following are some of the problems on wet friction to understand the overview of the concept.

Problem 1

Calculate the wet friction coefficient if F is given as 8N, the area is given as 10m, and the velocity gradient as 0.1/s?

Solution: One of the formulas to calculate the coefficient of wet friction is used below to solve the problem,

Substitute the values in the above formula,

8 = * 10 * 0.1

= 8 / 10 * 0.1

= 8

Therefore, the result of the coefficient of wet friction is 8

Problem 2

Find the value of wet friction coefficient if they have given the total wet frictional force as 20N and the normal force acting perpendicular on it is 28N?

Solution: The formula to calculate the coefficient of wet friction is given as follows,

F = N

Substitute the values in the above formula,

28 = * 20

= 28/20

= 1.4

Therefore, the value of the coefficient of wet friction is obtained be 1.4

Problem 3

A kid spills the water on the ground, here find the value of wet friction coefficient if they have given the total wet frictional force as 16N and the force acting perpendicular on the basis as 23N?

Solution: The formula to calculate the coefficient of wet friction is as follows,

F = N

Substitute the values in the above formula,

23 = * 16

= 23/16

= 1.43

Therefore, the value of the coefficient of wet friction is obtained be 1.43

Problem 4

Calculate the wet friction coefficient when a lubricant is added between the sideways of a door and given that F is 20N and the area of grease/ lubricant applied is given as 29m. The velocity gradient is given as 0.8/s?

Solution: The formula to calculate the coefficient of wet friction is used below to solve the given problem,

Substitute the values in the above formula,

20 = * 29 * 0.8

= 20 / 29 * 0.8

= 0.551

Therefore, the result of the coefficient of wet friction is 0.551

It is time to conclude by knowing some essential FAQs based on wet friction.

Frequently Asked Questions on Wet Friction | FAQs

Why do we feel difficult to move on a wet marble?

We feel challenged to move on a marble surface made up of marble due to its nature.

We know that for friction to occur, there is a need to have irregularities on the surface. Water spills on the marble surface cover all the microscopic gaps that lead to low friction. Therefore, making it difficult for the movement.

Can we eliminate friction?

We cannot wholly eliminate friction.

Any two surface in contact consistently exhibits some friction, whether it may be of significantly less value but cannot wholly eliminate it due to the presence of small pourings present on the surface that cause friction with substantially less effect.

Can friction oppose the direction of water in a container?

We cannot give any value of the wet friction coefficient to water.

For water, no criteria or factors of wet friction can be applied. But it can act as a lubricant that can help in reducing friction on a surface. Therefore, as it acts as a lubricant, the direction of water cannot be changed by a container.

Why is there less friction on wet surfaces?

Liquid or fluid matter has lesser irregularities.

When you spread the liquid on the surface, it covers all the irregularities supposed to produce opposing force for the surface in contact. Due to this, there will be low shear of liquid that reduces the amount of friction compared to the previous dry friction and makes the surface slippery.

Which one among dry and wet surfaces creates more friction?

Sometimes water may be the sole cause for an increase or decrease in friction.

Usually, dry friction causes more force of friction. Whereas in wet friction, the liquid decreases the friction between tires and the ground. But in some cases, we can observe that water present between fingers and paper causes high friction. So any friction can cause an increase in the force of friction.

Which friction is preferred more?

Wet frictional is more effective in showing the working of an object.

In general, we all prefer wet friction; wet is preferred more due to the tendency to remove frictional heat with the help of water or air.

Is there the presence of friction on a wet surface?

Of course, there will be a minimum amount of friction present on all the surfaces.

Let’s consider an example of our human skin. When we apply a lotion on our hands, the skin becomes automatically smooth, causing the wet friction coefficient to be activated, and in some cases, it is slightly high compared to dry friction.

Which constitutes more friction, dry or wet?

Dry surfaces have more amount of friction in comparison to wet surfaces.

On a dry surface, there will be more coefficient of friction as there will be a high tendency to produce opposing force. On wet surfaces, the wet friction will become significantly less in terms of coefficient of friction, and the opposite force is less.

Does rain reduce the force of friction?

Rain can bring change in the effect of friction.

We know that water spread in a certain amount acts as a lubricant. Before heavy rain, there will be only two surfaces, i.e., the surface of the vehicle tire and a dry surface of the street. But after rainfall, a new layer is introduced between the dry surfaces that lead to the drop in friction.

Also Read:

• How to find normal force with coefficient of friction
• Where is friction not useful
• How to find constant velocity with friction
• How to find acceleration with coefficient of friction
• Example of kinetic friction
• Bad friction
• Table without friction
• What is wet coefficient of friction
• Difference between friction and viscosity
• Find coefficient of friction given velocity and distance

Dry friction is the resistive force that encounters between the two solid surfaces. We can observe dry friction around us.

Earth gravitational pull is also an example of dry friction. We can experience the dry friction while you are walking, brushing, rubbing, sanding, etc. Without dry friction, we cannot imagine our life. Some dry friction examples are listed in this post.

Dry Friction Example

• Lightning matchsticks
• Brushing teeth
• Ironing clothes
• Writing on a paper
• Mopping the floor
• Rubbing hands
• Ball-bearing
• Page flipping
• Kid’s slide
• Walking on ground
• Sanding
• Cycling on the road
• Brakes on the automobiles
• Tug of war
• Climber plants
• Gecko lizards on the wall
• Forest fire
• Water well pulley

Lightning matchsticks

When the matchsticks are a strike against the rough surface, dry friction is created. Stick catches fire due to the friction. It is an example of kinetic friction, which is converted into heat energy.

Brushing teeth

Some sticky particles are deposited on the teeth, which is very challenging to remove. Brushing creates a maximum force to overcome the dry friction acting on the particles, and it is removed from the teeth.

Ironing clothes

When we start to iron the clothes, friction permits us to create pressure on the wrinkles on the clothes. The pressure eliminates the wrinkles. If the dry friction is absent, the iron box slides over the clothes. The pressure exerted on the clothes affect the friction acting on the wrinkles. This pressure directly related to the friction force.

Writing on a paper

An essential application of friction is writing on paper. The friction acting between the paper and the pen allows the ink molecules to stick on the paper surface.

Mopping the floor

The deposition of dirt and some particles on the floor are difficult to remove by normal dusting. Mopping with water creates a force to overcome the friction on the dust, and it is removed from the floor. The friction acting on the dust particles is static friction. It is one of the major household dry friction example.

Rubbing hands

Rubbing hands is a very good kinetic friction example. This is associated with the production of heat—the friction developed by rubbing causes to keep the hands warm.

Ball-bearing

If the friction acting on the machines is more, ball-bearing is used to reduce the friction. It uses the method of rolling friction. These are used in almost all the machines for ease move and to work smoothly. So ball-bearing is a dry friction example used in machines.

Page flipping

Flipping pages from one page to another, friction is necessary. The friction between the two pages allows us to flip to the next page. Without friction, flipping becomes complicated; the page might slip from our hands.

Kid’s slide

Sliding over the kid’s slides is very joyful that we are all enjoyed in our childhood days. Sliding friction is acting over the kid’s slide. When we slide down, the friction retards our motion and stops the immediate falling down.

Walking on ground

A very important dry friction example in every day life is walking. We are walking firmly on the ground due to friction force. Walking in the desert is difficult because the friction between our foot and sand offer low friction. So it is clear that friction is very necessary to walk on the ground.

Sanding

Sanding is a process to achieve the smoothness from the hard material. It is used to rub the wooden surface and edges.  The irregularity in the wooden surface is broken downs by the rough surface of the sandpaper, and hence the surface and the edge become smooth. This is used to reduce friction.

Cycling on the road

When we ride on the cycle, we start, stop, and can turn whenever we need. Friction acting between the cycle tire and road prevents from skidding on the road. The asymmetry on the cycle tire provides the necessary grip to hold on the road. Gripping allows the cycle to overcome from the friction because it has low value of friction coefficient.

Brakes on the automobiles

Brakes are another major dry friction example .The principle involved in the brakes of automobiles is friction. There is friction acting between the brake pad, and the wheel exerted when you apply, making the automobile stop the motion.

Tug of war

It is a game where two teams pull a rope on their side. There is friction between the hands of the people and the rope, which helps to hold a rope and provide grip to exert a force to pull. Since friction acting between the two solid surface it is a dry friction example.

Climber plants

We can see varieties of climber plants in nature, it is natural dry friction example. They can easily climb the wall, trees, gates, etc. it is because of friction. They generally use the rough surface to climb.

Gecko lizards on the wall

The gecko lizards climb the wall vertically so easily because of the friction. The frictional force between the leg and the wall is so strong so that it provides the grip to climb the wall.

Forest fire

Sometimes, the forest catches fire automatically because of the friction. When two trees rub each other, a frictional force is produced, which turn into thermal energy resulting in fire catching.

Water well pulley

An excellent example of rolling friction is the water well pulley. A rope is tied with a bucket full of water is drawn from the well with the help of a pulley. It is easy to pull out the bucket from the well due the friction force acting between the rope and the pulley.

Also Read:

• Where is friction not useful
• Difference between friction and viscosity
• How to find coefficient of kinetic friction
• Find coefficient of friction given velocity and distance
• Why static friction is greater than kinetic
• Relative motion in friction
• How to find normal force with coefficient of friction
• Example of kinetic friction
• Is friction a conservative force
• Wet friction

It is hard to move from one place to another without friction. But what is friction force? Is Friction A Conservative Force or non-conservative? Here we are going to discuss these questions.

When two objects slide or rub on each other, friction occurs between them. This friction tries to stop the relative motion of these two bodies by applying some force on each body. This force is called friction force. As the friction force depends on the path, so it is not a conservative force.

Friction: A necessary evil 

When two bodies move relative to each other and slide or rub on each other, friction occurs. Friction force always acts opposite to the direction of the motion. Friction is a necessary evil for motion, it is a self-adjustable force and depends upon the surfaces of bodies that are come in contact, or we can say it depends upon the path in which the relative motion occurs.

We can walk just because of friction, a bus can move from one place to another only because of friction, a bullet fired from a gun slows down due to friction, etc. So what is friction? What is friction force? Is it a conservative or non-conservative? Let us discuss these questions in detail.

Friction is mainly of two types,

• Static friction
• Kinetic friction

Static friction– The opposing force comes into play when a body tries to move over the surface of another body, but the actual motion that has yet not started is called static friction. E.g., a book on a shelf, a car in a parking lot, a metal cube on a table surface, etc.

                 The equation for the force of static friction is,

Where,

            N – a normal reaction

Kinetic friction– Kinetic friction is friction between two bodies in moving conditions. Kinetic friction is always the opposite of the motion and tries to stop the motion, such as friction between the road and a moving car, friction between sliding wooden cube on an inclined plane surface, etc.

The equation for the kinetic friction

Where –

μ_k-coefficient of kinetic friction

              N -normal force

Nature of friction force

Forces are of two types’ conservative forces and non-conservative forces.

Conservative force –

The force that depends on the initial and final displacement of the object and does not depend upon the path of motion is called conservative force, for example, gravitational force, electrostatic force, etc. In conservative force, work done is independent of path. Total energy under conservative force remains constant.

Non-conservative force –

 The total energy does not remain constant under the influence of non-conservative force forces. In the non-conservative forces, work done is depends upon the path by which motion occurs. The friction force, tension, and force over a wooden block are examples of non-conservative forces.

So from the above discussion, we can say that the friction force is non-conservative because it depends on the path. To understand it more accurately, consider a metal cube on an inclined plane,

Firstly we place that metal cube on a smooth surface inclined plane. In this case, the cube quickly moves on a surface because the friction between the cube and the inclined plane is very weak. Therefore cub can easily slide down on a smooth surface.

Now place the same cube over a rough surface inclined plane of the same inclination as a smooth plane. In this plane, the cube needs to do more work to slide over an inclined plane. Here, the friction between the cube’s surface and the inclined plane is greater than the smooth surface. Hence friction depends upon the path of motion, and that’s why it is a non-conservative quantity.

FAQ’s

What is normal force?

We can stand on the ground because of this force.

The ground exerts a force of reaction on the object equal to its weight is called the normal force. This force is always perpendicular to the surface.

What is limiting friction?

The definition of limiting friction is as follows.

When the applied force exceeds the static friction force, the body starts to move. So limiting friction is the maximum value of static friction up to which the body remains in the state of equilibrium.

What is the angle of friction?

The angle between the normal reaction and the resultant limiting friction is called the angle of friction.

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