d
(d)Initial momentum = \(\vec P = mv\hat i + mv\hat j\)
\(|\vec P| = \sqrt 2 mv\)
Final momentum = \(2m \times V\)
By the law of conservation of momentum
\(2m \times V = \sqrt 2 \;mv\)==> \(V = \frac{v}{{\sqrt 2 }}\)
In the problem \(v = 10m/s\) (given)
\(V = \frac{{10}}{{\sqrt 2 }} = 5\sqrt 2 \;m/s\)