Binding Energy and Energy Release in Radioactive Decay...

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MSB47
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"A group of unbound nucleons that are widely separated, their total potential energy is considered to be zero. As they come together and form a nucleus, they will lose potential energy...Hence, energy of a stable nucleus is less than that of the unbound nucleons required to make it up"

I understand that when nucleons are fused together to make the stable nucleus energy is required to hold them together via strong nuclear force in which mass will be converted to energy (E=mc2) and therefore the difference between energy of unbound nucleons and stable nucleus is called the binding energy however, what confuses me is in that paragraph if the total potential energy is zero how can it lose potential energy when its formed into a nucleus?

Secondly, when an unstable nucleus undergoes decay and produces a daughter nucleus and a decay product (i.e alpha or beta particle). Why does the combined mass of the daughter nucleus and the decay product come out to be less than the original parent nucleus?

Sorry for the long essay I can't seem to get a grasp on this concept :confused:
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tiddlytom
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For the potential energy, you can set where zero is. It's the same way as if you set zero gravitational energy to be you standing on the earth, if you jump into a hole you have "negative potential energy".

For the second part, energy is conserved. E^2 = (pc)^2 + (mc^2)^2 where p is the momentum. If the decay products have momentum, they won't have the combined mass of the parent.
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MSB47
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(Original post by tiddlytom)
For the potential energy, you can set where zero is. It's the same way as if you set zero gravitational energy to be you standing on the earth, if you jump into a hole you have "negative potential energy".

For the second part, energy is conserved. E^2 = (pc)^2 + (mc^2)^2 where p is the momentum. If the decay products have momentum, they won't have the combined mass of the parent.
so for binding energy; if you were to push unbound nucleons to form a nucleus, the energy required to push them together is that the binding energy or is it the energy that keeps the nucleons together in the nucleus?

and for the radioactive decay, is it because energy is released during the decay that lower the mass due to E=mc2? thanks for your help its cleared up alot of confusion
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tiddlytom
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(Original post by MSB47)
so for binding energy; if you were to push unbound nucleons to form a nucleus, the energy required to push them together is that the binding energy or is it the energy that keeps the nucleons together in the nucleus?

and for the radioactive decay, is it because energy is released during the decay that lower the mass due to E=mc2? thanks for your help its cleared up alot of confusion
The binding energy is the energy that holds them together.

As above, E^2 = (pc)^2 + (mc^2)^2, not just E=mc^2. Energy is conserved, so if some goes into momentum, you "lose" some mass.
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MSB47
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(Original post by tiddlytom)
The binding energy is the energy that holds them together.

As above, E^2 = (pc)^2 + (mc^2)^2, not just E=mc^2. Energy is conserved, so if some goes into momentum, you "lose" some mass.
ahh ok thanks for clarifying that for me
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