NUCLEAR PHYSICS

Worked Solutions

Binding Energy

calculations involving loss of mass

information

Example #1

Calculate the binding energy(in MeV) of an alpha particle from the following info. :

(ans. to 1 d.p.)

mass of a proton = 1.0076 u

mass of a neutron = 1.0090 u

mass of an alpha particle = 4.0028 u

1 u = 931 MeV

mass of particles in alpha particle = 2 protons + 2 neutrons

= 2(1.0076) + 2(1.0090) = 4.0332 u

mass loss(mass defect) = 4.0332 - 4.0028 = 0.0304 u

since 1 u = 931 MeV,

binding energy = 0.0304 x 931 = 28.3 MeV

Answer: binding energy of an alpha particle is 28.3 MeV

Example #2

Calculate the total energy released(in MeV) when uranium 238 decays by alpha emission to Thorium 234?

uranium 238 = 238.0508 u

thorium 234 = 234.0436 u

alpha partice = 4.0026 u

1 u = 931 MeV

mass loss(mass defect) = 238.0508 - (234.0436 + 4.0026) = 0.0046 u

since 1 u = 931 MeV,

energy released(MeV) = 0.0046 x 931 = 4.3

Answer: energy released from uranium 238 decay is 4.3 Mev

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