1. The problem statement, all variables and given/known data To calculate the height of the potential barrier for a head on collision between two deuterons given that each deuteron is a sphere of radius R 2. Relevant equations Potential of the first deuteron at a distance of 2R from it =V = ke/2R where k = 9 * 10^9 , e= 1.6 * 10^-19 Coulombs The potential energy of the system of 2 deuterons = V*e 3. The attempt at a solution Since the potential energy is the work required to be done in order to bring the second deuteron in contact with the first, the value of this potential energy should be the potential barrier. However, the answer given is half the potential energy as the potential barrier. I am unable to understand as to why this should be so. Either the answer as given is incorrect, or there is some flaw in my reasoning. Would appreciate some help in this regard. Thanks.