Posted by Amelia on Sunday, November 22, 2009 at 12:48am.
The Moon's period of revolution around the Earth is 27.3 d. How far away is the moon?

Physics  drwls, Sunday, November 22, 2009 at 2:18am
You need to know the mass of the earth (M) to answer that question. You can look it up or use the relation
g = G M/r^2,
where g is the universal constant of gravity, r is the Earth's radius and g is the acceleration of gravity at the Earth's surface.
To get the radius R of the moon's orbit, use Kepler's third law.
G M/R^2 = V^2/R = [(2 pi R)/P]^2/R
which rearranges to
R^3/P^2 = M G/(4 pi^2)
where P is the period in seconds.
For another explanation see
http://wwwistp.gsfc.nasa.gov/stargaze/Skepl3rd.htm
Answer This Question
Related Questions
 Physics  A satellite is placed between the Earth and the Moon, along a straight...
 science  The pull of gravity keeps the Moon in orbit around Earth. The distance...
 physics  Moon is a natural satellite of the Earth, circling it with period (...
 physics  A satellite is placed between the Earth and the Moon, along a straight...
 Physics  A satellite is placed between the Earth and the Moon, along a straight...
 Physics  A satellite is placed between the Earth and the Moon, along a straight...
 Physics  The earth has about 80 times the mass of the earthâ€™s moon. The ...
 physics  What two facts did Newton need to be able to calculate the ...
 physics  What two facts did Newton need to be able to calculate the ...
 physics  What two facts did Newton need to be able to calculate the ...
More Related Questions