28. A sphere with the same mass and radius as the original cylinder, but a smaller rotational inertia, is released from rest from the top of the ramp. K. and K. are the sphere's and the cylinder's total kinetic energy at the bottom of the ramp, respectively. How do K and K, compare, and why?

(A) K. c, because the sphere will gain less rotational kinetic energy.

(B) Kc, because the sphere has a greater acceleration and therefore has less time to gain kinetic energy.

(C) Kc, because both objects accelerate at the same rate.

(D) Kc, because the gravitational force does equal work on each object as it rolls down the ramp.

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