If we suppose that one object is losing contact from the floor, let's say the trajectory of this object is a semisphere, then in this instantaneous time just before the contact is loss will make the friction forces due to the floor disappear?
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1$\begingroup$ Obviously, as the moving object loses contact with the floor, its friction with the floor will go to zero. Is this what you're asking, or is it something else? $\endgroup$– Daniel GriscomDec 14, 2015 at 23:54
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$\begingroup$ Yes, I was asking exactly what you answered. I just asked to make sure of one assumption that I've made in an exercise, thanks. $\endgroup$– SciMolDec 15, 2015 at 0:39
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1 Answer
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The classic approximation for the force of friction is $$F_f = \mu F_N$$ While the frictional force in reality is more complicated, it's a pretty good approximation for many everyday circumstances.
Therefore, in the instant when the object is leaving the surface (and afterwards), $F_N = 0$, by the above equation, $F_f = 0$.
