The external force of all external forces and internal force in the system system is constant, and its kinetic energy is conserved.
For a single object (quality point), its synergy is zero or the number of yuan and zero, then its kinetic energy is conserved.
Depending on the dynamic canal
as the vector and f = 0, or When all force is done and f · DL = 0, the system is always constant, that is,
or write as:
For certain external forces and internal power, the system is unforgettable or zero, using kinetic conservation can solve certain problems.