A person sits on a freely spinning lab stool that has no friction in its axle. When this person extends her arms, A) her moment of inertia increases and her rotational kinetic energy remains thesame. B) her moment of inertia increases and her rotational kinetic energy decreases. C) her moment of inertia decreases and her rotational kinetic energy decreases. D) her moment of inertia increases and her rotational kinetic energy increases. E) her moment of inertia decreases and her rotational kinetic energy increases.

In an old-fashioned amusement park ride, passengers stand inside a 3.0-m-tall, 5.0-m-diameter hollow steel cylinder with their backs against the wall. the cylinder begins to rotate about a vertical axis. then the floor on which the passengers are standing suddenly drops away! if all goes well, the passengers will “stick” to the wall and not slide. clothing has a static coefficient of friction against steel in the range 0.60 to 1.0 and a kinetic coefficient in the range 0.40 to 0.70. part a what is the minimum rotational frequency, in rpm, for which the ride is safe? express your answer using two significant figures. f f = rpm