Two bodies are dropped from a height in successive intervals of half a second.  The relative velocity of one with respect to the other is

Initial velocity = 0
Velocity of one body after one second
$\left({\mathrm{v}}_1\right)=\mathrm{g}\left(1\right)=\mathrm{g}$
Velocity of other body after $\frac{1}{2}$ second
${\mathrm{v}}_2=\mathrm{g}\left(\frac{1}{2}\right)=\frac{\mathrm{g}}{2}$
Velocity of one body with respective another
$\begin{array}{l}={\mathrm{v}}_1-{\mathrm{v}}_2\\ =\mathrm{g}-\frac{\mathrm{g}}{2}\\ =\frac{\mathrm{g}}{2}\end{array}$