Q:

What is sliding friction?

A:

Quick Answer

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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Full Answer

In engineering, sliding friction occurs in numerous types of sliding components, such as journal bearings, cams, linkages and pistons in cylinders. Static friction is the friction required to move two surfaces that are not in relative motion.

The sliding coefficient of friction is normally much lower than the static coefficient of friction. This difference can be experienced when braking a car in slippery conditions. If the wheels lock up, the primary friction between the tires and the ground changes from static friction to sliding friction because the tires are no longer rolling with the ground speed, and the car will not decelerate as quickly.

Rolling friction occurs in components involving rolling motion such as ball bearings, roller bearings, wheels and linear bearings. Some components such as the gears involve a combination of both rolling and sliding friction.

When examined very precisely, however, all devices involving rolling friction technically involve sliding friction as well. This is because all rolling objects deform under contact pressure, even if only microscopically, resulting in sliding motion in addition to rolling motion.

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Related Questions

  • Q:

    Why is static friction greater than kinetic friction?

    A:

    Static friction is greater than kinetic friction because of irregularities between the static object and the surface upon which it rests. The irregularities mesh together making it more difficult to start movement than to keep the object in motion.

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  • Q:

    How do you find the coefficient of friction?

    A:

    To find the coefficient of friction between two surfaces, divide the maximum frictional force that can occur when one body is moving or has reached equilibrium and cannot move by the normal reaction force. The quotient represents the friction the two surfaces have with one another.

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  • Q:

    Why is friction good?

    A:

    According How Stuff Works, friction is good because it prevents sliding while walking, it protects vehicles from skidding by slowing them down, and it makes writing possible. Friction occurs when two surfaces come into contact. Excess friction hinders movement, and it wastes energy. Friction refers to a force that opposes motion. It is important because it is applied in almost all life processes.

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  • 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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