(m1-m2)010+2m202 碰前 m tm 20 a B (m2-m)020+2m1 碰后 m1+m2 讨论 a B (1)若m1=m2则v1=020,02=010 (2)若m2>m1且020=0则1≈-010,02≈0 (3)若m2<m1且720=0则0≈00,02≈20（1）若 m1 = m2 则 1 20 2 10 v = v , v = v （2）若 且 0 v20 = m2  m1 则 , 0 v1  −v10 v2  0 （3）若 m2  m1 且 v20 = 1 10 2 10 则 v  v , v  2v 讨 论 1 2 1 2 1 0 2 2 0 1 ( ) 2 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 A m1 m2 10 v  20 v  B v1  2 v  A B 碰前 碰后