Einstein’s mass-energy relation emerging out of his famous theory of relativity relates mass (m) to energy (E) as E= mc2, where c is speed
of light in vacuum. At the nuclear level, the magnitudes of energy are very small. The energy at nuclear level is usually measured in MeV,
where 1 MeV = 1.6 x 10-13 J; the masses are measured in unified atomic mass unit (u) where, 1 u = 67 x 10-27 kg.
(a) Show that the energy equivalent of 1 u is 931.5 MeV.
(b) A student writes the relation as 1 u = 931.5 MeV. The teacher points out that the relation is dimensionally incorrect. Write the correct
(a) Using Einstein’s mass-energy relation, the energy that is equivalent to the given mass can be calculated
1 amu = 1 u = 1.67 × 10-27 kg
Applying E = mc2
E = 931.5 MeV
b) As E = mc2
m = E/c2
Which means that 1u = 931.5 MeV/c2
The dimensionally correct relation of 1 amu = 931.5 MeV