Question

If you moved to a planet that has the same mass as the earth but twice the diameter, how would your weight be affected?

Answer 1

High jump records would not last long on this planet.

F_e is your weight on earth.
2* (r_e) is the radius of the planet you move to
r_e us the radius of the earth.
F_n is your weight on the new planet.

F_n / F_e = (2*r_e)^2 / (r_e)^2
F_n = 4 * F_e

See if you can figure out all the cancellations if you start with F_e = G * test_mass * M_earth /(r_e^2)