Friction is an everyday physical phenomina and yet the an accurate mechanisms basic it at the microscopic scale are still not totally understood. Research right into friction is vital for progressed nanotechnology. That is vital in everyday life although frequently we expend a lot of effort to try to minimise the effects and so reduce energy loss and also wear and tear on moving parts.

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What is Friction?

Friction is the name given to the pressure that opposes the activity of one human body sliding end another. It is called friction as soon as the objects room solid, viscosity in liquids but it constantly opposes the activity of an object.

The first mathematical description was do by Charles Augustine de Coloumb in 1764. He proposed the friction might be classed as static or dynamic and proposed the the frictional pressure was frictional force dependent on the materials in contact.

Surface Contact

At one interface between two objects, the surface may show up to it is in smooth, yet on a microscopic range the surfaces room pitted and jagged. When another similar surface is in contact with it, the irregularities and also peaks interlock. Australian Physicist, open minded Philip Bowden who worked on friction is quoted as saying: "Putting 2 solids together is quite like transforming Switzerland upside down and standing the on Austria—the area of call would be small."


Microscopic irregularities of smooth surface ar in contact.

The friction force depends on two factors:a) The products that are in contact. The two materials and the nature of your surfaces. Rougher surfaces have higher coefficient the frictions but to on slide apart. This renders sense in terms of a design in i m sorry friction is described as arising from chemical bonds in between the atom of the two surfaces at their points the contact: an extremely flat surface allow more atoms to come in contactb) The pressure pushing the 2 surfaces together. Advertise the surface together causes the more of the asperities come come together and also increases the surface area in call with each other.These have the right to be summaried v the equation, $F = mu F_N$ whereby $F_N$ is the normal force and also $mu$ is the coefficient the friction. Recognized as Coloumb"s equation.

Experimental determination of the Coefficient of friction, μ

A weight is inserted onto the inclined ramp. The load will desire to slide but is prevented native doing therefore by the frictional force in between the two poignant surfaces.

If the ramp is inclined further, the frictional pressure will flourish until the point that the is unable to avoid the mass indigenous sliding. Just prior to the weight slides, we room at the limiting friction.

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

$$F_N= mgcos( heta)$$

At the suggest of limiting friction, the friction force is equal to the ingredient of the weight force parallel come the steep of the ramp.

$$mu F_N=mgsin( heta)$$Substuting because that $F_N$ gives: $F = mu F_N$

Equating terms:

$$mgsin( heta) =mu mgcos( heta)$$

Rearranging for $mu$

$$mu = an( heta)$$

Experimental decision of coefficient the friction.

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

Dynamic Friction or Kinetic Friction

A microscopic version of friction treats the surface in contact as being continually, external inspection by small springs the form, strech and also break.<1>

Once an object has began to move, the irregularities of the surface need to run over each other. Revolution friction i do not care dynamic friction or kinetic friction. The moving surfaces perform not have actually time to form as plenty of bonds where the surfaces room in contact and also so kinetic friction is less than static friction. However due come the nature of the surfaces, any type of contamination or grease can alter the results dramatically. When an excellent care is taken to ensure that the surfaces space smooth and also extremely clean at the microscope level, the distinction between static and dynamic friction room more an overwhelming decern.


Nanotribology is the examine of friction and also wear procedures on the nanometer scale. In force microscopy, friction pressures arise once the probing guideline slides over the sample surface with a well-defined regular load. They are detected together torsion that the cantilever sustaining the tip. ~ above some products friction deserve to be traced down to the atom scale.

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Wide car Tyres and Friction

Why do high-powered dare have wide tyres if friction doesn"t rely on surface ar area? wide tyres have far better grip, but as we have actually shown, the coefficient of friction walk not depend on the surface ar area. Over there are many factors at work-related in the tight of a tyre, not just friction. In the very first instance, it might not be that you room comparing prefer with like. More comprehensive tyres space made of softer link of rubber, which have actually a better coefficient friction. Wider tyres additionally have lower sidewalls for less deformation in cornering which readjust the geometry of the tyre. Additionally friction that a genuine rubber tyre on tarmac roadway is very different come the friction ide that is demonstrated in the lab. ~ above the road, grip and also this is more than just friction, there is a keying the the rubber right into the tarmac, choose the meshing that gears this produces extr force to store the auto on the road. So raising the width of the tyre does rise the chance of grip being maintained. For an effective cars, we also want to minimize the beginning of wheelspin, which would certainly then be a trouble of kinetic friction through a lower coefficient that friction.