For years, marine scientists were mystified by sound waves detected by underwater microphones in the pacific ocean. these so-called t-waves were among the purest sounds in nature. eventually they traced the source to underwater volcanoes, whose rising columns of bubbles resonated like organ pipes.
a typical t wave has a frequency of 7 hz. knowing that the speed of sound in seawater is 1530 m/s, show that the wavelength of a t wave is 219 m.

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