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    the gravitational field strength at the surface of the earth is 6 times its value at the surface of the moon. The mean density of the moon is 0.6 times the mean density of the earth.

    What is the value of the ratio (Radius earth/Radius moon)

    I have volume earth x density earth = mass earth

    & volume moon x density moon = mass moon

    for mass earth

    (4/3)PixR^3x0.6p=m

    4/3xPixR^3xp=6m

    (5/4)mp=PixR^3
    (18/4)mp=PixR^3

    3.6m1p1/m2p2=(r^3)/(r2^3)

    appologies about the typing I got ratio of massxdensty=ratio of radius? The answer is 3.6 but I dont know how it relates to radius
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    you've probably done it already...

    The field strength at the surface is proportional to m/r^2 so you get a r^3 factor in the mass on the top of each of your fraction (as you've been doing) and a r^2 on the bottom, which cancels to just an r on the top.
 
 
 
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