1. The problem statement, all variables and given/known data The question can be found on this link. It is the last question, the one with the DNA molecules. Prof said that the direction is not important, he is just looking for a magnitude. http://www.phys.uvic.ca/medphys/people/AJ/Courses/Phys216/Assignments/P216-A1-2007.pdf 2. Relevant equations Coulomb's law: F=kQq/r^2, where k is 8.987x10^9 3. The attempt at a solution I can get the force between the O and H-N combination of molecules...I think. For thymine and adenine: F1 = k(0.2e)(0.4e)/(0.280nm - 0.1nm)^2 for the first bond between adenine and thymine. But I don't know how to get the force between N and H-N. Are there H's connected to those Nitrogen atom's? If so, would the force just be F2 = k(0.4e)(0.4e)/(0.300nm - 0.1nm)^2 Thanks!