What causes friction?
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Q:

What causes friction?

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Quick Answer

The primary causes of friction are surface roughness, the plowing effect and molecular adhesion. Surface roughness is when serious abrasion occurs due to the roughness of the materials in contact. The plowing effect involves deformations of the objects that cause resistance to movement when the materials are relatively soft.

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Full Answer

Adhesion refers to the molecular force that results from two materials brought into close contact with one another. To slide objects against each other, it is essential to break the adhesive bonds between them. According to recent scientific studies, friction occurs because of adhesive forces between materials. Ultra-smooth and sticky materials fall under the molecular adhesion category.

There are varying degrees of surface roughness in solid materials. Even a smooth surface has small bumps that interfere with sliding motion. When the surfaces of two hard, solid materials are very rough, friction occurs due to the abrasion that happens when two objects slide against each other.

Deformations are another cause of friction. Deformations form when soft materials deform under pressure and lead to an increase in resistance to motion. For example, when a person stands on a rug, he sinks in slightly, causing resistance as he drags his feet along the rug’s surface. Resistive force is created, and friction occurs when the deformation becomes large.

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Related Questions

  • Q:

    How is friction unhelpful?

    A:

    Friction is a force that opposes motion, so it is unhelpful in all situations where the motion of an object is desired. A by-product of friction is that energy is wasted in the form of heat, which can cause problems in temperature-sensitive environments.

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  • Q:

    How do you increase friction?

    A:

    The way to increase friction is to make the surfaces of two objects more difficult to slide against each other. This can be done by making the surface rougher or applying more pressure to one of the surfaces. For a solid and a liquid, friction can be increased by making the liquid thicker.

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  • Q:

    Why does friction occur?

    A:

    Friction is caused by the bumps on the surface of one object colliding with the bumps of another object's surface. All surfaces have bumps, created by their molecular structure. These bumps may only be visible on objects with seemingly smooth surfaces through the use of a microscope.

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  • Q:

    What is sliding friction?

    A:

    Sliding or kinetic friction is the drag force that results from two surfaces being pressed against each other while moving in relative motion. The sliding coefficient of friction is the dimensionless factor of this pressing force, resulting in the drag force for two specific surfaces.

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