
(b) Let $k$ be the spring constant of each half part of the spring. For a complete spring, the spring constant $k^{'} = k/2$
(springs in series). When two splitted parts of a spring are connected to the body, then the springs are in parallel. Their effective spring constant, $k^{'} = k + k = 2k$
As $T = 2\pi\sqrt{\frac{m}{k}}\ \ \ or\ \ \ T \propto \frac{1}{\sqrt{k}}$
$\therefore\ \ \frac{T^{'}}{T} = \sqrt{\frac{k/2}{2k}} = \frac{1}{2}\ or\ T^{'} = \frac{T}{2}$