A e, dr==.dr=d(r. r)=d(r")=dr 2r 2r 得W12=2-k(-b)dr 即Wk (12-6 2 2) 子A 式中1=1-l022=n2-l0 弹性力的功也与路径无关1 1 2 d d d( ) d( ) d 2 2 r r e r r r r r r r r r 因  =  =  = = 1 1 0 2 2 0 式中  = r −l , = r −l W k r l r r r ( )d 12 0 2 1 得 =  − − ( ) 2 2 2 2 12 =  1 − k 即 W 弹性力的功也与路径无关