相对运动 V2+U()v(元=Ev() y(x)=R(r)Ym(O,) x(r)(e, g) x+n2(E-O()-(+1xz=0 x>O,->0;F->∞ x相对运动 1 0, 0; ] 0 ( 1) ( ( )) 2 '' [ ( , ) ( ) ( ) ( ) ( , ) ( )] ( ) ( ) 2 [ 2 0 2 2 2 2 = → → →  = + + − − = = −  + =                 dr r r r l l E U r Y r r x R r Y U r x E x l m l m     