Q: A particle of mass m is thrown upwards from the surface of the earth. With a velocity u . The mass and the radius of the earth are respectively, M and R . G is gravitational constant and g is acceleration due to gravity on the surface of the earth. The minimum value of u so that the particle does not return back to earth, is

(a) $\sqrt{2 g R^2}$

(b) $\sqrt{\frac{2 G M}{R^2}}$

(c) $\sqrt{\frac{2 G M}{R}}$

(d) $\sqrt{\frac{2 g M}{R^2}}$

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Ans: (c)