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toothpaste666
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Homework Statement
On the surface of Planet X, the gravitational acceleration is 2g. If the diameter of Planet X is 1/3 that of Earth's, what is the mass of Planet X, expressed as a multiple of Earth's mass?
Homework Equations
[itex] F=G\frac{m1m2}{r^2} [/itex]
The Attempt at a Solution
let Mx = mass of planet x, Me = mass of earth, Rx = radius of planet x and Re = radius of planet earth. the diameter of planet x is 2Rx and the diameter of Earth is 2Re.
[itex] 2Rx = \frac{2Re}{3} [/itex]
[itex] Rx = \frac{Re}{3} [/itex]
we have
[itex] a = \frac{GMx}{Rx^2} = \frac{GMx}{(\frac{Re}{3})^2} = \frac{9GMx}{Re^2} = 2g [/itex]
since 2g = [itex] \frac{2GMe}{Re^2} [/itex] we have
[itex] \frac{9GMx}{Re^2} = \frac{2GMe}{Re^2} [/itex]
[itex] GMx = \frac{2GMe}{9} [/itex]
[itex] Mx = \frac{2Me}{9} [/itex]
Is this correct?