# Friction in Physics

I've heard a lot of things about Friction like friction between solids, liquids and gases. Even practical applications like motion of objects (Like car moving on road), etc. involve friction. But, do we really need to concern about Friction. I mean, Is the presence of friction really important in practical life? I goggled through but, i can't understand the depth of it, as all are saying "This wouldn't happen & That wouldn't happen" without friction...

Answers differentiating presence and absence of friction would be appreciated...

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It's a good thing that friction exists, otherwise nothing would stay where it should be. The slightest breeze would blow cars to the other side of the street, and if you push a chair aside it will slide all the way to the wall instead of stopping after 5 cm. Friction will slow it down very fast if you stop applying a force to it. You wouldn't be able to place anything on a table which wouldn't be perfectly level.

The left part of the graph shows static friction. The object will push back with the same force as applied, so it doesn't move. That's linear; if you push twice as hard it will push twice as hard back. Until you overcome a threshold when it starts to move, and then suddenly everything goes a lot smoother: you don't have to push as hard anymore. You're in the range of dynamic friction.

In low friction $F_{S(max)}$ will have a low value, but it still will be there. Imagine a skater on ice. You still will need a bit of force to get her moving, just a little bit, but even less once she's moving.

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Without friction there would be so many different things! We walk because of friction, we can write on paper because of friction. To put it simple, it is attached to us in our everyday life. While calculating the amount of force required to love a particular body, we have to take the account of limiting friction. If it is greater than the limiting friction, then only the body moves. When you are holding something against the wall, it is not the force you apply that keeps the thing on It's place, it is because of the friction that opposes the motion which prevents it from slipping. So we can say, that friction is indeed a necessary evil. Hope I could explain the importance of friction in simple words! :)

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Friction is present in the macroscopic and microscopic world as a resultant force. It is an important (nonconservative) force in classical mechanics because it makes certain types of motion, like walking, and the absence of motion, like resting on a chair, possible.

Friction is possibly absent in the quantum mechanical world, although there doesn't seem to be consensus yet, see this article about quantum friction.

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