3) 瞎貓死鼠解.

來源: jinjing 於 2011-09-18 08:16:45 [] [舊帖] [給我悄悄話] 閱讀數 : (140 bytes)
回答: a hole on earth: 由 jinjing 於 2011-09-13 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.

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