Planet X has the same radius as Earth but twice Earth’s mass. Which statement best explains how the weight of an astronaut standing on Planet X compares with her weight on Earth?
(a) It is about 2 times as large because gravitational force is sometimes taken to vary with the square root of the planet’s mass.
(b) It is about twice as large because gravitational force is directly proportional to the planet’s mass while the radius is unchanged.
(c) It is about four times as large because both the planet’s mass and the radius appear squared in the gravitational relationship.
(d) It is nearly the same because the astronaut’s own mass does not change when she travels to Planet X.