[领域] 大学普物 (题目相关领域) [来源] University Physics 12e Hugh D. Young Chapter8 的第108习题 [题目] 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.若动能和动量同时守恒 则两个氢原子无法结合成氢分子吗 还是指 2.解释 两个氢原子无法成为氢分子是因为动量和动能无法同时守恒 如果是1的话 我的想法是..碰撞过程中净外力为0，所以动量守恒 因为结合成氢分子要释出potential energy，碰撞前後所以动能不守恒 就好像非弹性碰撞，两个分子碰撞後会散失能量 所以动量和动能同时守恒 则两氢原子无法结合成氢分子 会像完全弹性碰撞弹开 --

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