Posted by hussain on Friday, May 4, 2012 at 2:12am.
two planets of masses m and respectively.have a centre to center separation of r.at what distance from the center of the pianet of mass m do the gravitational force of planets cancel each other???

al mustafa publick school  Steve, Friday, May 4, 2012 at 3:46pm
Assuming you meant masses M and m, then we need at distance d from M,
M/d^2 + m/(rd)^2 = 0
M(rd)^2 + md^2 = 0
(M+m)d^2  2Mrd + Mr^2 = 0
d = r/2 * (M+√Mm)/(M+m)
just as a sanity check, it's easy to see that d=r/2 when M=m
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