Draw a plot of potential energy of a pair of nucleons as a function of their separation. Mark the regions where the nuclear force is repulsive. Write any two characteristic feature of nuclear forces.

Define the terms binding energy for a nucleus and state the relation between the binding energy and mass defect.In nuclear reaction the $B.E$ per nucleon of the product nucleus/ nuclei is more than that for the original nucleus/nuclei. Is the nuclear reaction exothermic or endothermic in nature? Justify your choice.