(a) Draw a plot showing the variation of potential energy of a pair of nucleons as a function of their separation . Mark the regions where the nuclear force is :
(i) attractive and (ii) repulsive.
(b) In the nuclear reaction
`n+underset(92)(235_(Uto))underset(54" ")(a_(Xe+))underset(b" ")(94_(Sr+2n))` determine the values of a and b .

Explanation

The variation of potential energy of a pair of nucleus as a function of their separation (r) is shown in fig.
We find that corresponding to r=OC=0.8fm, P.E. is minimum. At this distance, force between nucleons=0. for distance `gt OC`, negative P.E. goes on decreasing. The nuclear force are attractive. for distance `lt OC`, negative P.E. decreases, becomes zero and then increases. The nuclear forces in this region are repulsive.