# Introductory physics hw

Hello, sorry if this is an easy question, but I don't quite get it.

Here it is:

Planet X is home to an alien culture called the Xinbar. The planets diameter is twice as large as the earth's and made out of the same stuff (i.e., the densities are the same). The Xinbar are made out of the same stuff as humans and weight the same on Planet X as we do on Earth. The equation for gravity is shown below, which reduces to mg near the earth's surface.

(note: I wasn't sure how to put in an equation since i'm new here, but its just the gravitation equation = mg)

(a) What is the volume of the earth?
(b) What is the volume of Xinbar? Determine the mass.
(c) What is the gravitational constant g on xinbar?
(d) We can model humans as cylinder roughly 6 ft tall and 2 ft wide. the Xinbar have roughly the same proportions, estimate how tall they are.
(e) Estimate how much a human would weigh on Planet X.

For part (a) I just used the equation for volume of a sphere using the earths diameter. Not sure if this particular problem suggest me to do it a different way.

I did the same for the first part in b, but not sure how to calculate the mass.

Any help would be appreciated. Thank you!