Q:

What causes friction?

A:

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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What causes friction?
Credit: Joel Penner CC-BY 2.0

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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:

    What does friction do?

    A:

    Friction is a force that tends to stop motion or resist the motion of objects. Friction is always a negative force, which means it acts in a direction opposite to the direction of the force applied to the object. Movement of objects through air and liquids gives rise to friction.

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  • Q:

    When does friction occur?

    A:

    Friction happens when one object slides along another object. It is the force that resists the relative motion between the two surfaces. Friction occurs in the opposite direction of the moving object's motion and reduces its speed.

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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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  • Q:

    What is helpful friction?

    A:

    Friction is considered helpful during situations such as, but not limited to, preventing slipping between the shoes and the floor during walking, preventing skidding between tires and the road while driving, in brake pads where friction causes the vehicle to stop, and in order to grip things to hold them properly. In all of these cases, friction is important and very beneficial to completing the task at hand.

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