All Textbook Topics - Forces and Motion - Friction, Lubrication and Viscosity - Lubricants reduce friction

Lubricants reduce friction

When you have two materials sliding over each other, you will get friction. Even surfaces that appear smooth, if looked at under a microscope, will be rough to some degree. See the first diagram below of a 'smooth' surface looked at under a microscope:

When two surface slide over each other, friction happens due to these surfaces rubbing against each other. The rougher the surface, the more friction there will be:

By putting a lubricant, such as oil, between the surfaces, the rough parts of the surface are in less contact as the lubricant is sitting between the two surfaces. This causes the amount of friction to reduce:

Previous
Static friction is a force applied to an object by a surface when you try to move the object. The object will only start to move once the force applied is greater than the static friction.
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Viscosity is an expression of how much internal friction there is in a fluid

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