13-4 Conservative of energy in a system of particles K +40 +ME Sys Sys sys, Int ext f (13-2) We illustrate these W principles by considering block-spring com bination shown in (b) Fig 13-4. the spring is initially compressed and then released Fig 13-4 Ch 13 Energy III: Conservation of energyCh.13 Energy III: Conservation of energy 13-4 Conservative of energy in a system of particles We illustrate these principles by considering block-spring combination shown in Fig 13-4. the spring is initially compressed and then released. (a) (b) (c) Fig 13-4 W f W f Ws f sys sys sys,int Wext ,F ΔK + ΔU + ΔE = (13-2)