Friction is a force that resists the relative movement between two surfaces. The surfaces can be any type – solid-solid, liquid-solid, solid-gas, gas-gas, liquid-liquid, etc.

Friction is a component that assumes importance in various studies as well as many aspects of daily life. Hence, the knowledge of friction calculation is necessary for everyone.

Our online friction calculator simplifies the calculation of static friction and kinetic friction. These are two important ones among various types of friction which we shall study as we move a little further on this friction calculator page.

Understanding Friction

Friction is a force that arises out of the roughness of the surfaces. Its nature is to prevent the motion of the surfaces. Friction is both helpful and unwanted depending on the situation that we deal with.

Consider the example shown below.

A boy tries to push a wooden block against the floor from rest.

Then, the force of friction that exists between the floor molecules and the wooden block molecules prevents the boy’s effort of pushing. Thus, friction always acts in the opposite direction of the push.

Factors affecting friction

According to the renowned French Scientist Charles-Augustin de Coulomb, known for Coulomb's law, friction depends on:

• the nature of the materials in contact with each other
• the surface area
• the normal pressure (or load), and
• the time for which surfaces are in contact.

Various studies also consider humidity, angle of inclination, temperature, and sliding velocity to calculate friction.

Types of Friction

The classification of friction depends on the context of the study.

Friction classification based on the nature of surfaces:

Dry Friction

It is the frictional force that comes into the picture when two dry surfaces try to slide over each other. Accordingly, there are two types of dry friction:

Static friction

Frictional force that exists between two static surfaces.

Kinetic Friction:

Frictional force that exists between two surfaces in motion.

Dry friction is mainly due to the unevenness of surfaces despite the smoothness they appear to be.

Fluid Friction

It is the frictional force that exists between the layers of a viscous fluid.

Lubricated Friction

When two surfaces have a lubricant in between them, lubricated friction comes into play.

Skin Friction

When fluid tries to slide over the surface of a body, skin friction plays its role.

Internal Friction

When you try to deform a solid substance, the internal friction opposes the motion between the elements that make up the solid.

Friction classification based on the other factors:

Rolling friction

Rolling friction comes into the picture when a body tries to slide up or down an inclined surface. Rolling friction depends on the angle of the inclined surface. Rolling friction is a type of kinetic friction and is always less than static friction.

Braking friction

The amount of friction that comes into the picture as a retarding force when we slow down a moving vehicle or a machine is called braking friction.

Properties of Friction

• Friction is an opposing force. It opposes the cause of the movement.
• Friction generates heat and energy. The friction produced between the surfaces of both hands turns into heat. It is why we feel warm when we rub both hands in winter.
• Friction causes loss of energy. You can observe this loss in the form of sound emitted by the running of heavy machines or as heat generated.
• Friction causes wear and tear of the equipment. Lubrication techniques such as greasing and oiling avoid this loss due to frictional wear and tear.

Calculation of Static Friction and Kinetic Friction

Before proceeding with the static friction and kinetic friction calculations, we should understand an important term: Coefficient of friction.

What is the coefficient of friction?

The coefficient of friction denoted by the Greek letter μ is the ratio of frictional force and the normal force acting on two surfaces.

• The normal force is the force that compresses two bodies over each other.
• Friction force tries to prevent the relative motion between two surfaces.

Thus, the coefficient of friction is calculated as μ= Force of friction/ Normal Force

Notes:

• The value of the coefficient of friction can range from zero to greater than one depending on the surfaces.
• The coefficient of friction is said to be the Coefficient of Static Friction (μ_s) if the objects are at rest.
• The coefficient of friction is said to be the Coefficient of Kinetic Friction (μ_k) if the objects are at rest.
• The value of μs is less than one in most practical cases. The value of μs also varies for the given two surfaces based on whether they are lubricated or not.
• Static friction and its coefficient are always greater than kinetic friction and its coefficient. It is because when two bodies are at rest, a greater number of frictional forces keep acting between their surfaces till the external force is enough to exceed this static friction and start their relative movement.

Formulae to calculate static friction and kinetic friction:

Static Friction (F_s)= Coefficient of Static Friction (μ_s) * Normal Force(N)

Kinetic Friction (F_k)=Coefficient of kinetic friction Friction(μ_k) * Normal Force(N)

Our friction calculator simplifies the calculation of friction coefficients. Just choose which parameter you want to calculate from the friction calculation formula and enter the other two values. Our online free friction calculator instantly gives you the answer in your choice of units of force. You can calculate both static friction and kinetic friction at a go using our online friction calculator.

Applications of friction

Friction plays a vital role in our life, right from simple daily activities to complex industrial mechanisms.

Walking: We cannot walk if there is no friction. Friction between the ground and our feet helps us in walking, standing, and moving.

Snow skating: Can you walk on ice? Doesn’t it feel slippery? That’s because the friction between ice and your foot is lesser than friction between normal ground and foot. Hence, we cannot walk on ice. However, this less friction makes ice skating feasible.

Tire design: Ever wondered why tires have treads and are not smooth? The treads on the tires help to increase friction when the ground is wet and aids in safe driving.

Matchsticks: The basic principle of generating fire by rubbing stones has friction hidden in it. Friction between two dissimilar substances is also the scientific principle behind the design of matchsticks.

Aircraft flying: It is a common experience that flights are delayed or canceled when the weather is cloudy or not suitable. It is because these clouds in such unsuitable weather can create static friction around the airplane, thus interfering with flight communication.

Industrial applications: Friction, if not taken care of, can cause industrial hazards ranging from fire to other accidents. Industries and heavy machinery hence use lubricants and insulation coatings etc. to prevent such hazards due to friction.

Asteroids in Earth’s atmosphere: Asteroids keep entering the Earth’s surface often. However, they are burnt before they enter the Earth’s surface. Do you know why? It is because of the friction that gases in the Earth’s atmosphere offer to the asteroid. Imagine if there is no friction! Scary, isn’t it?

Forest fires: In extreme summers, the friction between branches of trees can lead to forest fires.

Sports: Sliding activities in water parks consider fluid friction in their design. Similarly, the cyclists' helmets are so designed that the air passing over their heads limits friction and helps their cycling.

FAQs about Friction

Who discovered friction?

Leonardo da Vinci was the first person to study friction. Though his findings never came out immediately, it was his work on the history of tribology that proves that da Vinci systematically studied friction, first in the world.

How would the world be if there were no friction?

If there were no friction, you would miss many things including walking, writing, and driving.

Is friction bad?

Friction is not always bad. It helps in many daily activities and is an essential force for the existence of human life. However, it is important to limit friction to healthy levels through various measures for safety, productivity and economy.

How to reduce friction?

You can reduce friction by using lubricants, polishing surfaces, and some special industrial practices.

Is friction a fundamental force?

Friction arises due to the property of surfaces. However, it is not a fundamental force. It is the unevenness of surfaces that results in friction.

What are the units of friction?

Friction is a force. Hence its unit is Newtons (N). Note that the coefficient of friction(mu) is dimensionless and has no units.

What is the study of friction called?

Tribology is the study of bodies in relative motion. Since friction comes into the picture when two bodies stay at rest or in motion, the study of friction falls under Tribology.

We are sure after reading the fascinating facts about friction on our friction calculator page, you are clear that friction is both useful and annoying. It all depends on how we use it. After all, is that not what science is about?

Happy calculating with our wide range of scientific calculators. If you need this friction calculator as a widget, drop us an email at calcualtorhut@gmail.com to get it free!!