At what point on the line joining Earth and Moon is the net gravitational field zero? (M_E = 81 M_moon)
ACannot be determined
BHalfway between
C9/10 way from Earth to Moon
D9/11 way from Earth
Answer & Solution
Correct answer: C. 9/10 way from Earth to Moon
Let d = distance from Earth, total separation D. GM_E/d² = GM_m/(D-d)². √(M_E/M_m) = d/(D-d). With M_E = 81 M_m: 9 = d/(D-d), so 9(D-d) = d, 9D = 10d, d = 9D/10. So 9/10 of the way to the Moon from Earth.
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