[問題] binding energy的問題

[nonoman (nono)]

[領域] 大學普物                            (題目相關領域)

[來源] University Physics 12e  Hugh D. Young

       Chapter8 的第108習題

[題目]
        When two hydrogen atoms of mass m combine to form a diatomic hydrogen
molecule(H2), the potential energy of the system after they combine is -△,
where △ is a positive quanity called the binding energy of the molecule.

(a) Show that in a collision that involves only two hydrogen atoms, it is
impossible to form an H2 molecule because momentum and energy cannot
simultaneously be conserved.
(hint: if you can show this to be true in one frame of reference, then it is
true in all frames of reference. Can you see why?)

(b) An H2 molecule can be formed in a collision that involes three hydrogen
atoms. Suppose that before such a collision, each of the three atomes has
speed 1.00*10^3 m/s , and they are approaching at 120° angles so that at
any instant, the atoms lie at the corners of an equilateral triangle. Find
the speeds of the H2 molecule and of the single hydrogen atom that remains
after the collision. The binding energy of H2 is △=7.23*10^-19 J, and the
mass of the hydrogen atom is 1.67*10^-27 kg.

完全不知道如何下手..

想法:.
(a)是指 1.若動能和動量同時守恆 則兩個氫原子無法結合成氫分子嗎
  還是指 2.解釋 兩個氫原子無法成為氫分子是因為動量和動能無法同時守恆

如果是1的話
我的想法是..碰撞過程中淨外力為0，所以動量守恆
因為結合成氫分子要釋出potential energy，碰撞前後所以動能不守恆
就好像非彈性碰撞，兩個分子碰撞後會散失能量
所以動量和動能同時守恆 則兩氫原子無法結合成氫分子
會像完全彈性碰撞彈開
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◆ From: 163.25.118.162
※ 編輯: nonoman         來自: 163.25.118.162       (10/17 14:14)
推 wen0034:這題目不懂
※ 編輯: nonoman         來自: 163.25.118.162       (10/17 15:47)
※ 編輯: nonoman         來自: 163.25.118.162       (10/17 15:50)
推 wen0034:這牽扯質能轉換問題　我覺得題目這樣出不恰當
→ n0lin:這是大學普物嗎???
→ n0lin:請原po解釋一下其中的道理