The masses and radii of the earth and moon are M1 , R1 and M2 , R2, respectively. Their centres are at a distance d apart. What is the minimum speed with which a particle of mass m , should be projected from a point mid-way between the two centres so as to escape to infinity ?

Q: The masses and radii of the earth and moon are M1 , R1 and M2 , R2 respectively. Their centres are at a distance d apart. What is the minimum speed with which a particle of mass m , should be projected from a point mid-way between the two centres so as to escape to infinity ?

(a) $\sqrt{\frac{G(M_1 + M_2)}{d}}$

(b) $2 \sqrt{\frac{G(M_1 + M_2)}{d}}$

(c) $\sqrt{\frac{G(M_1 + M_2)}{2 d}}$

(d) $\sqrt{\frac{2 G(M_1 + M_2)}{d}}$

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Ans: (b)