d
(d) Let \(x\) be the point where \(K.E. = P.E.\)

Hence \(\frac{1}{2}m{\omega ^2}({a^2} - {x^2}) = \frac{1}{2}m{\omega ^2}{x^2}\)

==> \(2{x^2} = {a^2}\)

==> \(x = \frac{a}{\sqrt{2}} =  \frac{a}{\sqrt{2}} = 2\sqrt{2}\,cm\)