A $4\mathrm{.}0$ kgkg object is undergoing simple harmonic oscillation and its movement is described by x$($t$)=$x$($t$)=4\mathrm{.}0$ mm cos$(1\mathrm{.}05$rad$/$st$0\mathrm{.}785$rad$).$ Find the xx position of the object at which the potential energy is half of the total mechanical energy.