$A$ point particle is held on the axis of a ring of mass $m$ and radius $r$ at a distance $r$ from its centre $C$. When released,it reaches $C$ under the gravitational attraction of the ring. Its speed at $C$ will be

  • A
    $\sqrt {\frac{{2Gm}}{r}\left( {\sqrt 2 - 1} \right)} $
  • B
    $\sqrt {\frac{{Gm}}{r}} $
  • C
    $\sqrt {\frac{{2Gm}}{r}\left( {1 - \frac{1}{{\sqrt 2 }}} \right)} $
  • D
    $\sqrt {\frac{{2Gm}}{r}} $

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