The free boy diagram of one person inside the rotor should have three vectors: weight down, friction up, normal to the center of the cylinder. Is friction force given by centripetal force * static friction coefficient? Normal and centripetal are the same vector in this problem. Is minimum velocity for a person to not slide down given by an equality between friction force and weight? Mass cancels out in both sides. The previous question makes me think there is a contradiction: weight of a person is not required to explain why the person "sticks" to the wall when the rotor is rotating. But I did use mass to calculate the friction force. In the second question I've noticed that the mass cancels out, but the equation gives me the impression that if v is high enough, friction would become greater than weight and therefore, person would slide up.