小球 A 和 B 的质量相同, B 球原来静止, A 以速度 u 与 B 作对心碰撞.这两球碰撞后的速度 v 1 和 v 2 的各种可能值中有
A.
- u , 2 u .
B.
u/ 4 , 3 u/ 4 .
C.
- u/ 4 , 5 u/ 4
D.
,
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