An 8-MeV neutron is inelastically scattered from a barium nucleus. What is the average energy of the emergent inelastic neutrons?

7.45 Mev

Explanation:

in this case we need to considerated the following formula

alpha = E/Eo

where:

alpha = (A - 1) square / (A + 1) square

and A is the mass number of nucleus, for this case the Ba is 56

so we replace the values

alpha = (56 - 1) square / (56 + 1) square

alpha = 55²/57²

E = 8*55*55/57*57

E = 7.45 Mev