Answer:
v = 10 [m/s].
Explanation:
The largest mass is that of 4 [kg], in this way the momentum can be calculated by means of the product of the mass by velocity.
[tex]P=m*v\\[/tex]
where:
P = momentum [kg*m/s]
m = mass = 4 [kg]
v = velocity = 5 [m/s]
Now the momentum:
[tex]P=4*5\\P=20[kg*m/s][/tex]
This same momentum is equal for the other mass, in this way we can find the velocity.
[tex]P=m*v\\20=2*v\\v=10[m/s][/tex]