Momentum of the system would remain conserved. Initial momentum =0 Final momentum should also be zero. Let masses be 2m,2m, and m Momentum along x-direction =2mv
∧
i
Momentum along y-direction =2mv
∧
j
Net momentum =√(2mv)2+(2mv)2=√2⋅2mv Now, 2√2mv=mv′ v′=2√2v