Friction originates when two surfaces slide over each other. There are many factors that affect friction. The frictional force is based on the interlocking mechanism and also on other factors like pressure and design. Let us understand the factors affecting friction with examples, quizzes, and links to research articles.
What are the factors affecting friction?
- Roughness/smoothness of the sliding object
- Roughness/smoothness of the surface
- shape or design of the object
- Normal force acting upon the sliding bodies
- Dry friction is independent of the surface area of a contact
- Type of friction involved (rolling or sliding)
- Sliding surface’s state of matter (solid/fluid)
The friction force depends mainly on the above-listed factors, let’s discuss them in detail.
1. The smoothness of the sliding object
Smooth surfaces slide over surfaces easily compared to rough ones. One can notice the irregularities at the microscopic scale. These irregularities hinder the sliding between the surfaces. Thus, the roughness higher is the more friction.
A snow-covered surface offers very little friction. Cyclists use tires with high irregularity (grip) to increase friction with the surface.
2. The smoothness of the surface
It is impossible to have perfectly smooth surfaces. Each surface will have its own roughness. This roughness, combined with the roughness of the sliding object, will give rise to friction. Other factors affecting friction include the force pushing the surfaces together, the type of materials involved, the temperature of the surfaces, and the presence of any lubricants or contaminants.
3. The force between the two bodies in the normal direction (perpendicular to the sliding direction)
The force in the normal direction (perpendicular to the sliding plane) will increase the interaction between the surface thus increasing the friction. Friction is thus directly proportional to the normal force applied. [f = μ * N, where μ is the coefficient of friction]
The force observed in the normal direction is generally the weight of an object. So, friction is directly proportional to the weight of an object. According to the animation above, it is easier to push a light object compared to a heavy object of the same material.
4. Friction also depends on the design of an object
Friction exists not only in solid surfaces but also in liquids and gases. However, compared to sliding against a solid surface like a road, air or water provides very little friction. When we deal with fluid friction, the design of the object becomes crucial, and factors affecting friction must be considered. Generally, a streamlined design is chosen to reduce friction.
Aircraft and fish use a streamlined designs in order to reduce friction.
5. Friction is independent of the area contact
Friction is directly proportional to the normal force but is independent of the area of contact. [f = μ * N, where μ is the coefficient of friction]
6. Type of friction involved (rolling/sliding)
Rolling friction is always less than sliding friction. The introduction of wheels is also a factor that can reduce friction drastically. Try sliding your suitcase compared to a stroller bag, you can feel the ease of movement due to the drastic reduction in friction. For example: roller skates reduce friction and hence allow us to move faster compared to normal shoes.
7. Sliding surface’s state of matter (solid/fluid)
Fluid friction is always generally less than dry friction. Fluid friction is the friction between an object and a fluid (liquid or gas). For example, lubrication works on the principle of fluid friction. During lubrication, a viscous fluid acts as a layer between two sliding surfaces and reduces the friction between them.
Quiz on the factors affecting friction
Read more in research:
Read this paper to understand how the roughness of beds can be a factor influencing the friction of waves which impacts the formation of lagoons and affect water flow. Link: https://www.mdpi.com/2073-4441/10/10/1348
The relationship between surface wetting and friction of a surface is not well understood. When a surface is wet, it is generally associated with being slippery. This paper explains the factors affecting adhesion. https://www.mdpi.com/2313-7673/5/2/28
carbon nanotubes (CNT) are advanced carbon materials with a diameter in the nano-range. They generally are used for their excellent electronic properties. This paper discusses how the incorporation of CNT in thin films affects friction. The relationship between surface roughness and the friction coefficient is explained. Link: https://www.mdpi.com/2313-7673/5/2/28
Factors affecting friction are an important aspect of flow simulations and river engineering. You can read this research paper to see what are the factors affecting pipe friction. Link: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0154408
See Also:
- What is a frictional force?
- Friction is a necessary evil
- What are the applications of friction in our daily lives?
- How can we increase friction? What are the ways of doing it?
- How can we decrease friction? What are the ways of doing it?
- Quiz on friction
- What is rolling friction?
- What is fluid friction?
- What is static friction?
- 50 Examples of friction in our daily lives
