Answer
$42\ kg. m/s$
Work Step by Step
The mass of the ball $m=1.2\ kg$
Speed at which hits the ground $v_i = -25\ m/s$
Rebound speed $v_f = 10\ m/s$
The impulse of the ball is equal to the change in momentum:
$J=\Delta P$
$J = mv_f - mv_i$
$J = m(v_f-v_i)$
$J=1.2\ kg (10\ m/s - (-25\ m/s))$
$J=42\ kg. m/s$
