Say we had an object moving at speed $v$ with only KINETIC friction (approximately $\mu$$R$) acting on it, I know that it will decelerate due to the net force and eventually come to a rest with $v=0$ after some distance $x$. I would like to know why does the frictional force $\mu$$R$ stop acting on the object once it comes to rest, as if it stayed acting on the object the object would accelerate in the opposite direction to it's initial $v$?
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$\begingroup$ Does this answer your question? Why does Friction not accelerate the body in this case? $\endgroup$– John RennieCommented Dec 3, 2022 at 9:01
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*When an object is not moving relative to a surface a static frictional force could act to prevent relative movement between the object and the surface.
So if there is no tendency for relative movement (object on flat surface) there is no frictional force on the other hand if the object is on a slope but not moving then the frictional force "adjusts itself" to a value such that the object does not slip relative to the slope up to a maximum possible value of $\mu_{\rm static} \times \text{normal force}$.
If the static frictional force cannot stop the object from sliding then a kinetic frictional force, $\mu_{\rm kinetic} \times \text{normal force}$, acts in such a way as to try and reduce the relaive motion between the object and the slope.
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$\begingroup$ I think you misunderstood maybe. What I'm saying is that if we had an object and applied a force greater than static friction, we both agree it would accelerate. Now we also both agree that on a rough surface this object would not go forever and would eventually come to a stop. What I'm asking is that why does the kinetic friction force suddenly stop acting on the object once it's slowed down to v=0. $\endgroup$ Commented Dec 3, 2022 at 9:01
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$\begingroup$ I meant to say kinetic friction instead of static $\endgroup$ Commented Dec 3, 2022 at 9:03
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$\begingroup$ @Mathguy I have amended my answer. The mechanism of interaction between two surfaces differs as to whether the surfaces are moving relative to one another or not. $\endgroup$– FarcherCommented Dec 3, 2022 at 9:07
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$\begingroup$ So if the object is no longer moving relative to the surface that's why the kinetic friction stops acting? $\endgroup$ Commented Dec 3, 2022 at 9:09
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