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    • Thread Starter

    Ok so I need to find the distance of moon from the earth using this equation > T = 4pi^2r^3/GM all in square root. I have input the G and M values but what is r and how do I find it? The question is below if anyone can help me!

    Where G is the gravitational constant = 6.67x10-11 Nm^2kg^-2
    M is the mass of the planet (kg) and r is the distance from the centre of the planet to the centre of
    the satellite (m).
    If the moon takes 27.3 days to orbit the Earth, use the equation to calculate its
    distance from the Earth if the mass of the Earth is 5.975x10^24 kg.

    T^{2}=\left(\dfrac{4\pi^2}{GM} \right) r^3

    T has to be in seconds:

    T=27.3\times 3600\times 24 = 2,358,720s

    Rearrange into formula for r and solve it.


    (Original post by mrpopodopalaus)
    r is the distance from the centre of the planet and satellite (m)
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