INTRODUCTION :
In everyday life, friction plays a vital role in almost every activity we perform. Walking, writing, driving vehicles, holding objects, and even the functioning of machines depends on friction. In engineering mechanics, friction is a fundamental concept that helps engineers analyze the behavior of bodies in contact.
Friction is defined as the resisting force that develops between two surfaces in contact when there is a tendency of relative motion between them or when such motion actually occurs.
Importance of Friction in our life:
- Vehicles could not move or stop safely.
- Machines would slip and fail to transmit power
- Structures would become unstable.
Causes of Friction: Although surfaces appear smooth to the naked eye, they are irregular at the microscopic level. These irregularities cause friction when surfaces are in contact. Main causes of the friction is as follows. The combined effect of these factors results in frictional resistance.
- Surface Roughness – Interlocking of microscopic asperities
- Molecular Adhesion – Attraction between molecules of contacting surfaces
- Deformation – Soft surfaces deform under load, increasing resistance.
Types of Friction : Friction can be broadly classified into the following three types:
| Dynamic Friction |
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| Once motion begins, static friction is replaced by kinetic friction. |
| Static Friction |
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| Static friction acts when a body is at rest and resists the initiation of motion. |
| Limiting Friction |
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| Limiting friction is the maximum value of static friction that occurs just before motion starts. |