Origin of Friction

In a dynamical system, friction is defined as the tangential resistant force generated by a sliding interface. We need to characterise surface roughness, which has statistical properties, in order to investigate friction. Friction has been shown to be concerned with surface topography, and friction investigation has traditionally been associated with determining the true area of contact and understanding the mechanism of mating contacts. 

Surface physics, for example, explains friction as the formation of adhesive junctions by interacting asperities and their shearing away, whereas continuum mechanics interprets friction as the interlocking and fracture of asperities.

Asperity contact is a difficult task involving complex dynamics that must be addressed in order to address the problem of real sliding.The feasible approach is to assume that the contact is quasi-static to some extent. The deformation of contacting asperities can be assumed to be linear and elastic in many applications with relatively smooth surfaces. Many problems require the contact to be extended to non elastic and nonlinear conditions, as well as to include dynamics.

What is Friction?

Friction is the force that prevents one solid object from sliding or rolling over another. Frictional forces, such as the traction required to walk without slipping, can be beneficial, but they also provide a significant amount of resistance to motion. Approximately 20% of an automobile’s engine power is consumed in overcoming frictional forces in moving parts.

The forces of attraction, known as adhesion, between the contact regions of the surfaces, which are always microscopically irregular, appear to be the primary cause of friction between metals. Friction is caused by shearing these “welded” junctions and by the irregularities of the harder surface ploughing across the softer surface.

Types of Friction

According to the journal The Physics Teacher, there are two types of friction: static and kinetic. Static friction occurs between two surfaces that are not moving relative to each other, whereas kinetic friction occurs between moving objects.

The resistance between moving layers of a fluid in liquids is known as friction, which is also known as viscosity. According to the journal Dysphagia, more viscous fluids are thicker in general, so honey has more fluid friction than water.

Friction can also be felt by the atoms within a solid material. For example, when a solid block of metal is compressed, all of the atoms within the material move, causing internal friction.

According to the American Physical Society, there are no completely frictionless environments in nature: even in deep space, tiny particles of matter can interact, causing friction.

Coefficient of Friction

According to the journal Physical Review Letters, kinetic friction occurs when two solid objects move against each other. The friction in this case is a fraction of the perpendicular force acting between two objects (the fraction is determined by a number called the coefficient of friction, which is determined through experiments). In general, the force is independent of the contact area and does not depend on the speed at which the two objects move.

Friction can also be seen in stationary objects. According to the journal Wear, static friction prevents objects from moving and is generally greater than the frictional force experienced by the same two objects when they move relative to each other. Static friction is what prevents a box from sliding to the bottom of an incline.

Mathematically it is represented as, 

μ = F/N

Where, μ = Coefficient of friction, F = frictional force, N = Normal Force

What is frictional force?

A high frictional force between two bodies is harmful due to surface abrasion and wear and tear, resulting in a reduction in the mechanical stability of the bodies (e.g., pipelines, industrial equipment). Abrasion and wear cause any coating to be gradually chipped away by deforming the surface, exposing it to corrosion. 

Furthermore, a high level of friction generates heat, which causes changes in the surface’s microstructure and structure deformation. This causes the stressed surface to be anodic in comparison to the low stressed areas, resulting in the formation of a corrosion cell at that point and exacerbating the corrosion process.

Application of Friction

• Friction assists us in walking.

• We can use a pencil or chalk to write on paper or on boards.

• Because of air resistance, the friction between the meteor and the atmosphere heats it up, causes it to burn, and causes it to shrink in size.

• Vehicle brakes are based on the concept of friction.

• Pulleys for drawing water from wells use friction to operate.

• A ladder leaning against a wall.

• Friction is used to start fires by rubbing wood against wood or stone against stone.

Conclusion

Friction has been shown to be concerned with surface topography, and friction investigation has traditionally been associated with determining the true area of contact and understanding the mechanism of mating contacts. The feasible approach is to assume that the contact is quasi-static to some extent. Friction is caused by shearing these “welded” junctions and by the irregularities of the harder surface ploughing across the softer surface. In general, the force is independent of the contact area and does not depend on the speed at which the two objects move. According to the journal Wear, static friction prevents objects from moving and is generally greater than the frictional force experienced by the same two objects when they move relative to each other.