A $200kg$ canon is on a flat icy surface, upon which it experiences no friction at all. The canon fires a

$10kg$ ball with a muzzle velocity of $100\frac{m}{s}.$ This is the speed of the ball, relative to the canon after

firing. Determine the speed of the canon ball as measured by an observer on the ground $($who is getting

shot at$!),$ after the canon is fired.