標題:
萬有引力 r=0
發問:
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根據萬有引力的公式 F=G(M1)(M2)/(r^2) 如果r=0 , F不是=無限大嗎? 為什麼F=0 更新: 但是我老師係以一個物質係地球內部地核中心同積分去講F=0 佢話咩畫一個交叉穿過個物質同畫一個圓形(以地心為圓心)既圓周係穿過果個物質 然後就話圓周外 交叉內 兩邊既兩部份質量引起既引力為抵銷 原本唔明- -可5可以俾積分過程同解釋下
最佳解答:
Simply speaking, gavitational force arises due to presence of mass, r = 0 means there is no mass at all. Hence there is no gravitational force. 2013-02-06 20:10:03 補充： In your teacher's example, the mass m is placed inside the earth and is enclosed by a spherical shell on the outside, and a sphere of radius r inside. The forces due to the outside spherical shell balance away. There is only gravitational force from the sphere where the mass m is on its surface. 2013-02-06 20:12:34 補充： But when r = 0, that means the sphere shrinks to zero. Obviously, there is no gravitational force. 2013-02-06 20:18:52 補充： You could refer to the following web-page for the mathematical derviation of the relevant formula: http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/earthole.html
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