Einstein’s Mass-Energy Equivalence – Practice


1) In a particular reaction in the Sun, a proton fuses with deuterium. 20MeV are produced as a result of this nuclear reaction.

a) How much energy is released in joules?

b) How much mass is lost as a result of this reaction?

2) 8.16 MeV were released as a result of a number of electron-positron annihilations. How many particles were involved to produce this energy?

3) When 1kg of coal is burnt it releases 3.4 × 107 J of energy. How much mass is lost when 1 tonne of coal is burnt in a power station?

Quick Answers:

1a) 3.2 × 10−12 J     b) 3.6 × 10−29 kg  

2) 16 particles (8 electrons and 8 positrons)

3) 3.8 × 10−7 kg

Worked Answers: