VISUAL PHYSICS ONLINE

 

SPECIAL RELATIVITY: Experimental Verifications

    NUCLEAR REACTIONS     

 

 

SUMMARY

 

Total energy

    total energy = rest energy + kinetic energy + potential energy

                       

 Law of conservation mass-energy   isolated system E = constant

 

 

 

 

UNITS

 

Most calculations of mass and energy in nuclear physics do not use S.I. units. Hence, we need to consider the units you will often encounter.

 

Mass

          atomic mass unit     1 u = 1.66053906660×10−27   kg  =  931.49410242  MeV.c-2

 

Energy

        electron-volt                  1 eV  =  1.602176634×10−19  J

                                            1 MeV   =   106  eV  =  1.602176634×10−13  J

 

 

 

CALCULATIONS FOR NUCLEAR REACTIONS

 

The mass and energies involved in nuclear reaction, perhaps provides the most direct confirmation of the law of conservation mass-energy and the equivalence of mass and energy. We can set up a mathematical model based upon the law of conservation of mass-energy that can be used for nearly all the nuclear reaction calculations you may encounter.  The nuclear reaction is summarized by the transformation of an initial state (reactants) to a final state (products). 

 

 

The Q-value (disintegration energy) for a reaction is the amount of energy absorbed  or released during the nuclear reaction. Q-values affect reaction rates. In general, the larger the positive Q-value for the reaction, the more likely is that it will occur and the faster the reaction proceeds.

 

A reaction with a negative Q-value  is endothermic (endoergic). A net energy input is required for the reaction to occur.

 

 A reaction with a positive Q-value  is exothermic (exoergic). Such a reaction may occur spontaneously with the release of energy as the kinetic energy of the newly created nuclei and electromagnetic radiation.