# Binding Energy

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Hey guys,

Doing a project on star formation and fusion. We did mass defects in class today, but we were using ${\Delta}E={\Delta}mc^2$. Seeing as the mass is the rest mass of an object, can this be applied to protons when they are both at rest and in the nucleus?

Thanks,

Dan

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if it is moving in your frame of reference, you use $E^2=(mc^2)^2+(pc)^2$

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But it's at rest..

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so the p in (pc)^2 is equal to zero. which makes (pc)^2 equal zero which leaves you with E^2=(mc^2)^2 which simplifies to E=mc^2. since not all mass is consumed you go back the equation you posted and that gives you the binding energy(the energy released)

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Thank you.

Just confused me having the rest mass change while it's stationary both in and out of the nucleus, stupid quantum physics

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You don't look at the rest mass of the proton or neutron while it's in the nucleus, you are looking at the rest mass of the nucleus itself. It will be less than the sum of the individual parts because it has given up the binding energy.

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