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The frictional force is a function of the force pressing the surfaces together and the coefficient of friction between the materials. In particular:
where Ff is the force of friction, Fp is the force perpendicular to the contact surface (usually called the normal force), and μf is the coefficient of friction.
The coefficient of friction (also known as the frictional coefficient or the friction coefficient) is a scalar value used to calculate the force of friction between two bodies. It is usually between 0 and 1. The coefficient of friction depends on the materials used -- for example, ice on metal has a very low coefficient of friction (they rub together very easily), while rubber on pavement has a very high coefficient of friction (they do not rub together easily). It is interesting to note that, contrary to common belief, the force of friction is unrelated to the size of the contact area between the two objects.
The force of friction is always exerted in a direction that opposes movement. For example, a chair sliding to the right across a floor experiences the force of friction in the left direction.
The coefficient of friction also depends on the type of friction. There are three general types of friction:
The coefficient of friction is an empirical measurement -- it has to be measured experimentally, and cannot be calculated.
Since the total amount of friction depends on the path an object takes, friction is not a conservative forceA conservative force is a force which is path-independent. In other words, in moving an object from point A to point B, the total work done is independent of the path that the object took. The term conservative force comes from the fact that when a conser.
Physical deformationDeformation is a change in shape due to an applied force. This can be a result of tensile (pulling forces) or of compressive (pushing forces) loads being applied. In the figure it can be seen that the compressive loading (indicated by the arrow) has cause is associated with friction. While this can be beneficial, as in polishingPolishing is the act of giving something polish, typically through rubbing. Polishing results in a smoother surface with higher shine. Polish can also refer to a compound used in the polishing process. There are two types of polishing: Adding a polish to, it is often a problem, as the materials are worn away, and may no longer hold the specified tolerancesTolerance in engineering is an allowance made for imperfections in a manufactured object. For example, an electrical specification might call for a resistor with a nominal value of 100 ohms, but should also state a tolerance such as "+ 1%". This means tha.
The work done by friction is released in the form of heat. This can translate into deformation and heat that in the long run may affect the material's specification and the coefficient of friction itself. Friction can in some cases cause solid materials to melt.
Friction may occur between solids, gases and fluids or any combination thereof. See aerodynamicsFluid dynamics Aerodynamics is a branch of fluid dynamics concerned with the study of gas flows. The solution of an aerodynamic problem normally involves calculating for various properties of the flow, such as velocity, pressure, density, and temperature, and hydrodynamicsFluid dynamics Hydrodynamics is fluid dynamics applied to liquids, such as water, alcohol, oil, and blood. Blaise Pascal in the 1600s contributed some of the initial theory to this field. The term originates from the work of Daniel Bernoulli, based on the. Also, friction occurs inside deforming objects.
A common way to reduce friction is by using a lubricantA lubricant (colloquially, lube is a substance introduced between two moving surfaces to reduce the friction and wear between them. Worldwide, more than 50 million tonnes of lubricants are consumed annually. Automotive engine lubricants comprise approxima that is placed between the two surfaces, often dramatically lessening the coefficient of friction. The science of friction and lubrication is called tribologyTribology derives from the Greek tribos meaning I rub''. Formally defined, it is the science and technology of interacting surfaces in relative motion and all practices related thereto. In other words, it is the science and technology of friction, lubrica. Superlubricity, a recently-discovered effect, has been observed in graphite: it is the total absence of friction between two sliding objects. This would correspond to a coefficient of friction of 0, long thought impossible.
Lubricants to overcome friction need not always be thin, turbulent fluids; acoustic lubrication occurs when sound (measureable in vacuum by placing a microphone on one element of the sliding system) permits vibration to introduce separation between the sliding faces. World War II Panzer tank treads lubricated by their own squeak provide the most famous, if serendipitous, example.
"Friction" is a track on Television's 1977 release Marquee Moon.
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