# Energy in nuclear reactions

I have two questions, been trying to get definite and intuitive answers to them for some time so hopefully you can help me:

1) I understand both the strong force and binding energy but what is the relationship between the two?

2) What actually causes energy to be released when nuclei fuse or split? In my high school textbook it says changing the average binging energy between nucleons causes energy to be released... could you please make this clearer?

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Let say we have the following nuclear reaction $$_{Z_1}^{A_1}X_1+_{Z_2}^{A_2}X_2\longrightarrow _{Z'_1}^{A'_1}Y_1+_{Z'_2}^{A'_2}Y_2+_{Z'_3}^{A'_3}Y_3+_0^0\gamma$$ then the difference of masses between the Xs and the Ys is converted to kinetic energy of the Ys and to energy of $\gamma$ (this also happens in chemical reactions).
Yes, I understand, but to make the claim true you have to examine every system at subnuclear scales and you have to take the mass of the fundamental particles to be a kind of potential energy (which is easy enough with, say a $Z^0$, but a little less clear with an electron). Telling that to a layman or a student just starting out will engender confusion because we routinely talk of other kinds of energy. On the whole, I don't like that formulation, but I haven't voted down because it is arguably true. –  dmckee Jul 14 '13 at 13:41