When Is Friction Its Greatest

This is the highest friction.Observe, that the lizard is literally fastened at the roof, and what is the normal reaction? Should be almost zero! So ladies and gentleman, you are looking at the highest friction found in nature.

Limiting friction is the maximum value of static friction, which occurs just before an object begins moving across a surface. Limiting and static friction are very closely related, however limiting friction will always be greater than or equal to the static friction, which is greater than the kinetic friction. When comparing values for the same system, the friction forces should be as such:Limiting friction ≥ Static friction > Kinetic frictionHowever, this will only hold true if you are speaking about one system. For example imagine a system of a brick on a surface of ice and another system with the same brick on a surface of pavement. Since ice generally has a low coefficient of friction compared to pavement, all of the frictional coefficient values in the system on ice should be lower than the ones on pavement. If you compare across the two systems, the static/limiting frictional forces on ice may be less than the kinetic friction force for the brick on pavement. This difference in surface characteristics means that you may find a kinetic friction force for the same object that is greater than your static/limiting friction force on the slicker surface (friction on pavement > friction on ice).It may be easier to get a brick to start sliding on ice (overcoming static/limiting friction) than it is to keep a brick sliding on pavement (overcoming kinetic friction). The amount the values differ will depend on the roughness of the pavement, even though the object you are trying to move is the same. As long as you are not comparing across multiple systems, the inequality that I laid out above should hold true. However, if you compare different systems/surfaces, you may find cases where the kinetic friction is greater than your static/limiting friction.

Two very flat, very clean metallic surfaces the atoms can form bonds which make friction very high.Friction and Coefficients of Friction shows dry aluminum-aluminum coefficient of friction 1.05 -1.35. The force of friction is the product of the coefficient of friction and the normal force. Here then is one example of what the question asked.

The Most Common Origin of FrictionFriction exists because most surfaces really look like this under a microscope.Note the hills, the crests and the valleys. These are called asperities, or material deformations. They occur on rough surfaces, and even flat surfaces might have minor irregularities on it.Now imagine trying to rub them against each other. Feel, for a moment, in your mind’s eye the opposition you are likely to encounter as they grind against each other.That grinding is the most common origin for friction, both static (when your object is still and you’re trying to get it to move) and kinetic (when your object is already moving, and you need to keep it moving).It is why the friction that wheels encounter while rolling (called rolling friction) is much lower than other types of friction, and why tyres have deep grooves in them. It is also why friction tends to decrease the flatter and more uniform your surface gets.Friction for Flat SurfacesBut friction can still exist for perfectly flat surfaces, where asperities of the form above are no longer present.Perfectly flat surfaces bond to each other - in other words, they try to stick to each other. This is called adhesion, and can be caused by any number of reasons:van der Waals forces, a class of forces where attraction between electric dipoles on the surface of the material cause them to be attracted. In such cases, the materials are said have been dispersively adhered.chemical bonding, where the atoms of the two materials exchange electrons in some way and become chemiially attached to each. For instance, hydrogen in one material may form tenuous bounds with strongly electronegative elements in the other.These forces are typically weak enough that they are easily broken once you lift the object - but not so weak that overcoming the attraction by dragging the object doesn’t pose a problem.Finally, a DefinitionFriction, then, is not so much a force as it is the sum of very tiny forces and irregularities along the edge of surfaces.It is possible to model it as a true force - and indeed, most high school textbooks do just that - but it is important to recognise that that is just a convenient abstraction. Friction is to forces what Santa Claus is to a jolly man in a fat suit: window dressing on top of a very complex reality.

Frictional force refers to the force generated by two surfaces that contact and slide against each other. It is the force that opposes the motion of the object. It is easy to explain that if the two bodies contact with each other then friction is developed. For example, the friction between the road and the tyre..simply u just make an attempt to rub ur hands with each other then heat is generated due to friction…it may be of different types..

Rolling friction is the force resisting the motion of a rolling ball or wheel (a curved surface). This type of friction is typically a combination of several friction forces at the point of contact between the wheel and the ground or other surface. It is the weakest type of friction (compared to static and sliding friction). This is the reason that wheels and ball bearings facilitates motion.Image credits:"Rolling Resistance 2" by AndrewDressel (talk) - I (AndrewDressel (talk)) created this work entirely by myself.. Licensed under CC BY-SA 3.0 via Wikipedia - File:Rolling Resistance 2.pngW is some vertical load on the axle, F is some towing force applied to the axle, r is the wheel radius, and both friction with the ground and friction at the axle are assumed to be negligible and so are not shown. The wheel is rolling to the left at constant speed.