Question -
Answer -
Let m, m1,and m2 be the respective masses of the parentnucleus and the two daughter nuclei. The parent nucleus is at rest.
Initialmomentum of the system (parent nucleus) = 0
Let v1 and v2 bethe respective velocities of the daughter nuclei having masses m1 and m2.
Totallinear momentum of the system after disintegration = 
Accordingto the law of conservation of momentum:
Totalinitial momentum = Total final momentum
Here,the negative sign indicates that the fragments of the parent nucleus move indirections opposite to each other.