During a circus act, a performer thrills the crowd by catching a cannon ball shot at him. The cannon ball has a mass of m$1=10\mathrm{.}5$ kg and the horizontal component of its velocity is v $=8\mathrm{.}55$ m$/$s when the performer, of mass m$2=66$ kg$,$ catches it$.$

$$ Part $($a$)$

If the performer is on nearly frictionless roller skates, enter an expression for his recoil speed, in terms of the masses and initial speed.