Question:
An amusement park ride consists of a circular, horizontal room. A rider leans against its frictionless outer walls,which are angled back at 30∘ with respect to the vertical, so that the rider's center of mass is 5.0m from the center of the room. When the room begins to spin about its center, at what angular velocity will the rider's feet first lift off the floor?
(A) 1.9rad/s.
(B) 2.3rad/s.
(C) 3.5rad/s.
(D) 4.0rad/s.
(E) 5.6rad/s.