反冲运动 火箭

助力高考-秒杀二级结论-《高中物理手册》第三版上市!

反冲

1、定义:一个物体在内力的作用下,分裂成两部分,一部分向某个方向运动,另一部分向相反的方向运动,这种现象叫做反冲。

2、特点:反冲过程中内力远远大于外力,系统的动量守恒。

反冲经典题型

1、一爆弹静止在光滑的水平面上,点燃后爆炸分为质量为m和M的两部分,质量为m的速度为v,求质量为M的部分速度为多大?

分析:爆弹在爆炸的过程中动量守恒,设爆炸后m的方向为正方向,爆弹作为研究系统。

由动量守恒:0=mv+MV’

解得V’=—mv/M(负号表示与规定的正方向相反)

2、静止的机关枪的质量为M,不断射出质量为m的n颗子弹,射出的速度为v,求最后机关枪的速度为多大?

分析:以机关枪和子弹为系统作为研究对象,在打出子弹的过程中动量守恒,设子弹的速度方向为正方向。

由动量守恒:0=nmv+MV’

解得:V’=—nmv/M(负号表示与规定的正方向相反)

动量守恒定律经典题型


高中物理知识点总结

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