On February 20, 1962, John Glenn became the first American to orbit Earth. If John Glenn weighed 640 N on Earth's surface,

a) how much would he
have weighed if his Mercury spacecraft had (hypothetically) remained
at twice the distance from the center of Earth?

b) Why is it said that an
astronaut is never truly "weightless?"

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