In s frame y W=W+2=「+ m m In s frame with velocity of vs relative to s frame X W=W+W2=f·c+f2·Chz (1-,)+|2(2-,n) ∫子+1的了的,山 =「f·+· W Ch 12 Energy II: Potential energyCh.12 Energy II: Potential energy 1 f  2 f  Ｏ 1 r  2 r  z y x m1 1 2 1 1 2 2 m2 W W W f dr f dr     = + =  +    In S frame: S In S’ frame with velocity of relative to S frame: s s v '  W' W' W ' f dr' f dr' 1 2 1 1 2 2     = + =  +    ( ) ( ) 1 1 2 2 f dr v dt f dr v dt s's s's       =  − +  −   f dr f dr (f f ) v dt s's        =  +  − +   1 1 2 2  1 2 1 2 f f    = − 1 1 2 2 f dr f dr     =  +   =W