Object a has mass m and is traveling forward with speed v. which set of changes to object a will not affect its momentum?
mass reduced to 0.5m, speed increased to 2v

mass reduced to 0.25m, speed increased to 1.25v

mass increased to 2m, speed increased to 2v

the direction of velocity reversed, speed kept at v

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