A pendulum is made of a small sphere of mass 0.250 kgkg attached to a lightweight string 1.20 mm in length. As the pendulum swings back and forth, the maximum angle that the string makes with the vertical is 34.0∘∘. Friction can be ignored. At the low point of the sphere's trajectory, what is the kinetic energy of the sphere?

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