We know that $v = u + at$, hence
$0 = u - gT \Rightarrow u = gT$
When $v = \frac{u}{2}$, then
$\frac{u}{2} = u - gt \Rightarrow gt = \frac{u}{2} \Rightarrow gt = \frac{{gT}}{2} \Rightarrow t = \frac{T}{2}$
Hence at $t = \frac{T}{2}$, it acquires velocity $\frac{u}{2}$
(બંને ટ્રેક વચ્ચેનું અંતર નહિવત લો)