A person stands at a point of 374m in front of the face of a sheer cliff. If the person shouts, how much time will elapse before an echo is heard? Assume the speed of sound is 344m/s

Holes drilled several kilometers into earth’s crust provide direct evidence about earth’s interior in the form of

The ability to make things happen is also called a. heat b. force c. matter d. energy

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