Q: A body is released from a point of distance R’ from the centre of earth. Its velocity at the time of striking the earth will be (R’ > R* _{e}*)

(a) $\displaystyle \sqrt{2 g R_e} $

(b) $\displaystyle \sqrt{ g R_e} $

(c) $ \displaystyle \sqrt{2 g (R’ – R_e) } $

(d) $ \displaystyle \sqrt{2 g R_e (1- \frac{R_e}{R’})} $

Ans: (d)