With what velocity should a particle be projected so that its height becomes equal to radius of earth?
${\left( {{{GM} \over R}} \right)^{1/2}}$
${\left( {{{8GM} \over R}} \right)^{1/2}}$
${\left( {{{2GM} \over R}} \right)^{1/2}}$
${\left( {{{4GM} \over R}} \right)^{1/2}}$
