送交者: chouqilozi 于 2009-11-04, 13:55:08:

回答: i did not say 机械能守恒 either - if so, sand grain would be bouncing 由 meiyou 于 2009-11-04, 13:01:14:

• hehe (无内容) - meiyou (0 bytes) 2009-11-04, 14:04:08 (380609)

加跟贴