Friction is an everyday physical phenomina and yet the precise mechanisms underlying it in ~ the microscopic scale are still not completely understood. Research right into friction is vital for progressed nanotechnology. It is necessary in daily life although frequently we expend a lot of initiative to try to minimise the effects and so reduce power loss and also wear and also tear on relocating parts.

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What is Friction?

Friction is the name provided to the force that opposes the movement of one body sliding end another. That is called friction when the objects room solid, viscosity in liquids yet it constantly opposes the movement of an object.

The very first mathematical summary was make by Charles Augustine de Coloumb in 1764. The proposed the friction might be classed as static or dynamic and also proposed that the frictional force was frictional force dependent ~ above the materials in contact.

Surface Contact

At an interface in between two objects, the surface may appear to be smooth, but on a microscopic scale the surfaces space pitted and also jagged. Once another comparable surface is in contact with it, the irregularities and also peaks interlock. Australian Physicist, candid Philip Bowden who operated on friction is quoted together saying: "Putting 2 solids with each other is fairly like transforming Switzerland upside down and also standing that on Austria—the area of contact would be small."


Microscopic irregularities of smooth surface in contact.

The friction pressure depends on 2 factors:a) The materials that room in contact. The two materials and also the nature of your surfaces. Rougher surfaces have greater coefficient of frictions yet to on slide apart. This provides sense in regards to a version in i m sorry friction is explained as developing from chemistry bonds in between the atom of the 2 surfaces at their points that contact: really flat surfaces allow an ext atoms come come in contactb) The force pushing the 2 surfaces together. Pushing the surface together causes the an ext of the asperities to come together and increases the surface area in contact with each other.These have the right to be summaried with the equation, $F = \mu F_N$ where $F_N$ is the typical force and $\mu$ is the coefficient of friction. Recognized as Coloumb"s equation.

Experimental determination of the Coefficient of friction, μ

A weight is put onto the inclined ramp. The weight will desire to slide however is prevented native doing for this reason by the friction force between the two emotional surfaces.

If the ramp is lean further, the frictional pressure will flourish until the point that the is can not to avoid the mass from sliding. Just before the weight slides, we space at the limiting friction.

$F=\mu N$ whereby $F$ is the frictional force, $\mu$ is the coefficient of friction and also $N$ is the normal force acting specifically to the surface ar of contact. Since the load is not relocating this pressure is equal and also opposite come the upright component that the weight pressure on the ramp, it is characterized by:

$$F_N= mg\cos(\theta)$$

At the allude of limiting friction, the friction pressure is same to the component of the weight force parallel come the steep of the ramp.

$$\mu F_N=mg\sin(\theta)$$Substuting for $F_N$ gives: $F = \mu F_N$

Equating terms:

$$mg\sin(\theta) =\mu mg\cos(\theta)$$

Rearranging for $\mu$

$$\mu =\tan(\theta)$$

Experimental decision of coefficient that friction.

What is fairly counterintuitive around this is, that mass, the surface ar area or the pressure of gravity influence the coefficient of friction only the 2 surfaces that room in contact. The values for the coefficient of friction for various pairs of products are tabulated from experimental results. The range of values is around 10-2 for smooth surface to 1 because that the roughest surfaces.

Dynamic Friction or Kinetic Friction

A microscopic design of friction treats the surface in call as gift continually, bonded by little springs that form, strech and also break.<1>

Once an object has began to move, the person who is abnormal of the surface should run over each other. Static friction becomes dynamic friction or kinetic friction. The moving surfaces do not have time to type as many bonds whereby the surfaces are in contact and also so kinetic friction is less than revolution friction. However due to the nature the the surfaces, any contamination or grease can transform the results dramatically. When an excellent care is taken to ensure that the surfaces space smooth and extremely clean at the microscope level, the distinction between static and also dynamic friction room more difficult decern.


Nanotribology is the research of friction and also wear processes on the nanometer scale. In pressure microscopy, friction pressures arise once the probing reminder slides end the sample surface ar with a well-defined typical load. They room detected together torsion that the cantilever sustaining the tip. Top top some materials friction deserve to be traced down to the atomic scale.

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Wide automobile Tyres and Friction

Why do high-powered car have large tyres if friction doesn"t rely on surface area? vast tyres have much better grip, however as we have actually shown, the coefficient that friction go not count on the surface ar area. Over there are countless factors at job-related in the fixed of a tyre, not just friction. In the an initial instance, it may not be the you room comparing choose with like. More comprehensive tyres are made that softer link of rubber, which have actually a better coefficient friction. Broader tyres additionally have reduced sidewalls for less deformation in cornering which change the geometry that the tyre. Additionally friction of a genuine rubber tire on tarmac road is an extremely different to the friction concept that is prove in the lab. Top top the road, grip and also this is an ext than just friction, there is a keying that the rubber right into the tarmac, choose the meshing the gears this produces added force to save the automobile on the road. So enhancing the broad of the tire does rise the opportunity of grip gift maintained. For powerful cars, we also want to reduce the beginning of wheelspin, which would certainly then be a difficulty of kinetic friction with a lower coefficient that friction.