conservation  Laws    In  any  physical  process  the following conservation laws always hold:

1.  Conservation  of  energy: If we consider a closed system, the  quantity S (m_oc² + E)  always  remains  constant.  Where S m_oc² is the total rest mass energy of the system, and S E is the total energy of all other kinds.

S ( m_oc²+ E ) = constant

2.  Conservation  of  linear  momentum:  When  the  resultant external  force  on  a system is zero, the total vector momentum remains constant.

P = constant, when F _external = 0

3. Conservation  of  angular  momentum:  When  the resultant external  torque  on a system is zero, the total angular momentum is constant.

L = constant, when t _external = 0

4. Conservation of charge: Total charge is conserved.

D Q = 0

In  processes  of  elementary  particles,  there  are  other quantities  which are conserved These   are  baryon number, lepton number, isotopic   spin, strangeness and  parity. These quantities  and  their  conservation laws are discussed in elementary particles.