The Earth is assumed to be a sphere of radius R. A platform is arranged at a height R from the surface of the Earth. The escape velocity of a body from this platform is fv, where v is its escape velocity from the surface of the Earth. The value of f is:-

Question

( A ) $\frac 1 3$
( B ) $\frac 1 {\sqrt 2}$
( C ) $\frac 1 2$
( D ) ${\sqrt 2}$