We can reverse the process as, both Nina and Matt are moving towards each other and the law of conservation of momentum says that after and before the collision the momentum are the same.(60*5)=(100*3)300 kg m/s = 300 kg m/sThe object which have less mass have more velocity this is prove by derivation of the impulse formulae.Force = mass*velocityVelocity = (v-u)/tForce *time = mass*velocityMass*velocity =momentumFt = momentumImpulse = ftFt = momentum