Why did physicists expect a hot filament to give off ultraviolet light as its temperature increased? a. they thought that light existed as particles of various energies. b. they thought that light could be absorbed or emitted only in specific-sized chunks. c. they thought that matter could emit only certain frequencies of light. d. they thought that as the energy increased, the frequency of light would increase.

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