A $0\mathrm{.}015$kg bullet is fired horizontally into a block of wood with a mass of $2\mathrm{.}5$kg and embedded in the block. Initially, the block of wood hangs vertically, and the impact causes the block to swing so that its center of mass rises $0\mathrm{.}15$m$.$ Find the velocity of the bullet just before the impact $($g$=9\mathrm{.}8$m$/$s$\mathrm{²}).$