本题目来源于试卷: gc textbook chapter 7 Linear Momentum，类别为 通用国际物理
[问答题]
A Superball is dropped from a height h ok7otb*h j0 o,into a hard s)7ytk:zb3 f/ g iermk;teel plate (fixed to the Earth), from which it rebounds at very nearly its original speed. (a) Is the momentum of the ball conserved during any part of this process? (b) If we consider the ball and Earth as7t gy/rkb)m z;:k ife3 our system, during what parts of the process is momentum conserved? (c) Answer part (b) for a piece of putty that falls and sticks to the steel plate.
参考答案: (a) The momentum of the ball is not conserved during any part of the process, because there is an external force acting on the ball at all times – the force of gravity. And there is an upward force on the ball during the collision. So considering the ball as the system, there are always external forces on it, and so its momentum is not conserved. (b) With this definition of the system, all of the forces are internal, and so the momentum of the Earth-ball system is conserved during the entire process. (c) The answer here is the same as for part (b)
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