A particle of mass `m` is placed at a distance `R` from centre of a uniformly dense thin ring of mass `m` rand radius `R` on a axis passing through its centre and perpendicular to its plane. Find the speed of the particle when it reaches at the centre fo the ring due to their mutual gravitation force.

Options

A. `sqrt((Gmsqrt(2)(sqrt(2)-1))/(R))`
B. `sqrt((Gm)/(2R))`
C. `sqrt((Gm(sqrt(2)-1))/(Rsqrt(2)))`
D. none of these