A mass m$=1\mathrm{.}4$kgm$=1\mathrm{.}4$kg hangs at the end of a vertical spring whose top end is fixed to the ceiling. The spring has spring constant k$=55$N$/$mk$=55$N$/$m and negligible mass. The mass undergoes simple harmonic motion when placed in vertical motion, with its position given as a function of time by y$($t$)=$Acos$($t$)$y$($t$)=$Acos$($t$),$ with the positive y$-$axis pointing upward. At time t$=0$t$=0$ the mass is observed to be at a distance d$=0\mathrm{.}45$md$=0\mathrm{.}45$m below its equilibrium height with an upward speed of v$0=5$m$/$sv$0=5$m$/$s$.$

Find the angular frequency of the oscillation, in radians per second.