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Two plates make up a V-shaped horizontal groove. Both of the plates are at an angle θ with respect to the ground. In the groove there is a section of rope of length L and of even mass distribution. All of the rope is located on the plane perpendicular to the groove so that both of the plates are touching the same amount of the rope. Above the bottom of the groove a part of the rope of length fL does not anymore rest on the plates. Find f if the rope is on the verge of slipping. The coefficient of friction between the rope and the plates is μ=1.