4. Two planets have masses M and m, and the ratio M/m = 25. The distance between the planets is R. The point P is between the planets as shown in the right, and the distance between M and P is x. At P, the gravitational force on an object due to M and m are equal in magnitude. The value of x is
(A) 5R/6
(B) 25R/36
(C) R/25
(D) 6R/5
(E) none of these.
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統計: 尚無統計資料
統計: 尚無統計資料