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Doubts:- Although he is stating that till now there is no effective model to explain kinetic friction. (1)Why Kinetic friction is independent of the contact area of the body with the surface?

(2)Why kinetic friction is independent of the velocity of the moving object?

$|\vec{F_k}|=\mu_k |\vec N|$. What if $\mu_k$ depends on the area of contact and velocty of the object? How do I know it is not?

Link to video


These are simply approximations like Hooke’s law. There is no reason it must be independent of either and it most likely isn’t in reality.

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    $\begingroup$ I mean, How do I prove it using mathematics? $\endgroup$ – Unknown x Jul 18 at 6:17
  • $\begingroup$ At this stage, it’s not something you could really prove but an assumption you make about your system. If we had more information about the materials, perhaps we could come up with something but in a general case, we simply assume this. There are however many other reasonable relations one can assume but this one best qualitatively and simply captures the phenomena of drag. $\endgroup$ – Aakash Lakshmanan Jul 18 at 6:19
  • $\begingroup$ Do you know any publication about the 'real' measured velocity dependent friction values? For stretching of materials not following hookes law there is a lot. $\endgroup$ – lalala Jul 18 at 6:44
  • $\begingroup$ Okay @ Akash Lakshmanan $\endgroup$ – Unknown x Jul 18 at 6:44

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