WEBVTT
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This is College Physics Answers
with Shaun Dychko.
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We are going to calculate the energy released
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in this neutron source
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when beryllium is bombarded
by alpha particles.
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Now we need to know what the atomic mass
of each of these isotopes are.
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So for helium-4, there's the atomic mass
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and here's beryllium-9 has that atomic mass
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carbon-12 is 12.00000 by definition
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and the mass of a neutron is this
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and to figure out the energy released,
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we have to find the difference
in total mass
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between the two sides of this equation
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and then convert that into energy.
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So the energy released then is the mass
defect is one way to put it
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or the change in mass times *c* squared.
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And so we have the mass of
the alpha particle
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plus the mass of beryllium-9
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minus on the right-hand side,
the mass of carbon
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and minus the mass of the neutron
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and that difference gets multiplied by
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931.5 megaelectron volts per *c* squared
for every atomic mass unit
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and so the atomic mass units cancel
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and then we multiply by *c* squared because
that's what this equation tells us to do
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and then these *c* squared's cancel
leaving us with
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5.701 megaelectron volts of
energy are released.