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Static vs Dynamic friction

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If I have understood it correct the static friction applies when an object is at a standstill. When you apply a force that is larger than the static frictionforce, dynamic(kinetic) friction applies instead. Now the dynamic friction is used as long as the object is in motion and as soon as the object comes to a halt(or near zero velocity), static friction is used again. Is this correct? Now what about Pacejka's Formula? Does it calculate the dynamic friction for a tyre?

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Guest Anonymous Poster
I'm not sure if I understand the question right, but..
Yeah, I think that's pretty correct: when the object is still and the external force applied is smaller than the force of "static" friction (I've always called it 'friction of rest') the object does not move.
When the applied force is greater than (or in some cases 'equal to') the force of friction of rest, the object begins to move, and the total force for your kinetical equation is a vector sum of external force and force of friction (dynamic friction, what you call it, I guess). And the force of friction remains the same (not - see below..)
That's what you are tought in school, which is of cource FALSE.
(Actually i'm surprised you ask this at the same time asking about Pacejka's formula, which is far more complicated.)
These friction formulas are all empirical, up to now no one has acually given an universal formula.
When the external force is greater than the static friction force, the object moves, and (for most non-liquid materials) the friction force becomes _less_ as the speed grows.
Of course if you want to realistically simulate tyre friciton you have to take that into account!
I suggest doing a google search for "Pacejka's formula". For me it at once gave some pages specifically on tyre friction.

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