Aman with a mass of 80.0 kg is out fishing with his daughter, who has a mass of 25.0 kg. they are initially sitting at opposite ends of their 3.0-m boat, which has a mass of 60.0 kg and is at rest in the middle of a calm lake. the man and the daughter then carefully trade places. we will neglect any resistive forces between the boat and the water. how far has the boat moved, once the man and his daughter have finished trading places?

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