\(A\) \(\rightarrow v_1\)    (\(B\))

                  rest

It undergoes completely inelastic collision

Using conservation of linear momentum

Initial momentum = Final momentum

\(\Rightarrow m v_1=m v_2+m v_2\)

\(\Rightarrow m v_1=2 m v_2\)

\(\Rightarrow \frac{v_1}{v_2}=\frac{2}{1}\)