m1010+m202=m1+m202 碰前 今m(n-)=m2(2-)可p四 20 B m102.⊥Lm0m0-m01+-m20 碰后 m(020-02)=m2(2-2) a B 解得 m1-m2)0o+2n20.0 (m2-m1)2+2m0 m1+m2 m1+2 2 2 2 1 1 2 2 2 0 2 1 1 0 21 21 21 21 m v + m v = m v + m v ( ) ( ) 2 2 0 2 2 2 21 2 1 1 0 m v - v = m v − v ( ) ( ) 1 10 1 2 2 20 m v − v = m v − v 1 10 2 20 1 1 2 2 m v + m v = m v + m v 解得 , ( ) 2 1 2 1 2 1 0 2 2 0 1 m m m m m + − + = v v v 1 2 2 1 2 0 1 1 0 2 ( ) 2 m m m m m + − + = v v v Am1 m2 v10  v20  Bv1  v2  A B 碰前 碰后