Q:

What is fluid friction?

A:

Quick Answer

Fluid friction is the resistance to an object's motion through a liquid or gas. When the motion is occurring in a liquid, it is referred to as viscous resistance. Resistance to an object moving through a gas, such as air, is termed air friction.

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Full Answer

The concepts of fluid friction vary depending on whether the motion is taking place in a liquid or gas. One item that both media share is that the resistance to motion contributes to an object reaching its terminal velocity. This occurs when the resistance from a gas or fluid is equal to the weight of the object, and it remains constant until another force is introduced.

For motion in a liquid, viscous resistance caused by a drag force is proportional to the velocity of the object at slow speeds. This drag force is based on the object's geometry and the viscosity of the liquid, which can vary between fluids. For motion through air, friction at slow speeds is proportional to the velocity. At higher speeds, the drag force depends on the cross-sectional area of an object, the object's density and the drag coefficient. This drag force has a negative value, as the resistance is always opposite the direction of velocity.

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Related Questions

  • Q:

    How does friction affect motion?

    A:

    Since friction opposes movement, it causes resistance that makes it harder for a sliding object to move, thus slowing down movement. Friction can be seen through the example of a car making a stop; the wheels and breaks cause friction, making the car slow down. In addition to affecting solid objects, friction also causes resistance with glass and liquids by causing a collision that results in heat.

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  • Q:

    What is wind resistance?

    A:

    Wind resistance, a type of friction also known as drag, is the relative opposing force imparted on an object as it moves against still air. The wind resistance on an object depends on the square of its velocity, so as the object accelerates, its velocity and wind resistance increase.

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  • Q:

    What is air resistance?

    A:

    Air resistance is the friction that objects experience as they move through an atmosphere made up of air. Air is made up of relatively widely spaced particles in the form of molecules and atoms. These minute particles, en masse, must be pushed against for any object to move.

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  • Q:

    What is static friction?

    A:

    Static friction is the resistance to movement when two non-moving solid objects are in contact with each other. Static friction matches applied force and prevents motion. When the applied force overcomes static friction, the object starts moving, and at this point, static friction ceases and kinetic friction comes into play.

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