Answer
n 1.) Use J=Δp    so……
J=10N.s(E)=Δp=10kg.m/s(E)
and since original p was 0kg.m/s
and Δp=10kg.m/s(E),
 new p=10kg.m/s(E)
then use….. p=mv     so……..
10kg.m/s(E)=5.0kg x v    so….

       v=2m/s(E)