A point P lies o the axis of mass M and radius r at a distance r form its centre C. A small particle starts form P and reaches C under gravitational attraction. Its speed at C will:

Q: A point P lies o the axis of mass M and radius r at a distance r form its centre C. A small particle starts form P and reaches C under gravitational attraction. Its speed at C will:

(a) $\sqrt{\frac{2 G M}{r}}$

(b) Zero

(c) $\sqrt{\frac{2 G M}{r}(1-\frac{1}{\sqrt{2}})}$

(d) $\sqrt{\frac{2 G M}{r}(\sqrt{2}-1)}$

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Ans: (c)