A body is released from a height equal to the radius (R) of the...

Using conservation of mechanical energy,

${U}_{i} + {K}_{i} = {U}_{f} + {K}_{f}$

$⇒ - \dfrac{GMm}{2R} + 0 = - \dfrac{GMm}{R} + \dfrac{1}{2}m{v}^{2}$

$⇒ \dfrac{1}{2}m{v}^{2} = \dfrac{GMm}{2R}$

$⇒ v = \sqrt{\dfrac{GM}{R}} = \sqrt{gR}$