\(v=100-10 \times 5\)
\(v =50 m / s\)
from conservation of momentum
\(1 \times 50 \hat{ j }=0.4 \times 25(-\hat{ j })+0.6 \overrightarrow{ v }\)
\(50 \hat{ j }+10 \hat{ j }=0.6 \overrightarrow{ v }\)
\(\overrightarrow{ v }=\frac{60 \hat{ j }}{0.6}=100 \hat{ j }=100 \;m / s \hat{ j }\)