Aknife thrower throws a knife toward a 300-g target that is sliding in her direction at a speed of 2.15 m/s on a horizontal frictionless surface. she throws a 22.5-g knife at the target with a speed of 39.0 m/s. the target is stopped by the impact and the knife passes through the target. determine the speed of the knife after passing through the target.

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