3) 瞎猫死鼠解.

回答: a hole on earth:jinjing2011-09-13 18:01:55

Stone is mg on the face and 0 in the center. So,in side,the near center the lighter,linearised,F(x)=x/R*mg,...We get the same answer.

请您先登陆,再发跟帖!