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在第一讲力学(一)中,已复习了牛顿运动定律这一动力学规律。本讲继续复习动力学的有关知识,其中包括功和能、动量和冲量。即大纲中的:四、物体的相互作用六、机械能等章内客。Ⅰ.复习要点一、知识结构物体的运动状态决定于力的作用效果。力的作用效果可以从瞬时效果、作用一段时间(时间积累)的效果、作用一段位移(空间积累)的效果等三个角度研究,由此分别总结出牛顿运动定律、动量定理和动量守恒定律、动能定理和机械能守恒定律,俗称三把力学金钥匙。具体列表如下: 二、重要概念和规律 (一)重要概念 1.功(W) 功是表示力作用一段位移(空间积累)效果的物理量。要深刻理解功的概念:①如果物体在力的方向上发生了位移,则就说这个力对物体做了功。因此,凡谈到做功,一定要明确指出是哪个力对哪个物体做了功。②做功必须具有两个必要的因素:力和物体在力的方向上发生了位移。因此,如果力在物体发生的那段位移里做了功,则物体在发生那段位移的过程里始终受到该力的作用,力消失之时即停止做功之时。③力做
In the first lecture on mechanics (1), the dynamic law of Newton’s laws of motion has been reviewed. This lecture continues to review the knowledge of dynamics, including work and energy, momentum and impulse. That is, in the outline: Fourth, the interaction of objects VI, mechanical energy, etc. I. Review points I. Knowledge Structure The movement of an object depends on the effect of force. The effect of force can be studied from three perspectives: the instantaneous effect, the effect of a period of time (accumulation of time), and the effect of a displacement (spatial accumulation), thus summing up the Newton’s laws of motion, the momentum theorem, and the law of conservation of momentum. Kinetic energy theorem and conservation of mechanical energy, commonly known as the three gold key to mechanics. The specific list is as follows: Second, important concepts and laws (A) important concepts 1. Work (W) Work is a physical quantity that expresses the force acting on a displacement (spatial accumulation) effect. To understand the concept of work in depth: 1 If the object is displaced in the direction of force, say this force has done work on the object. Therefore, when it comes to doing work, it must be clearly pointed out which force has done work on which object. 2 Work must have two necessary factors: Force and object are displaced in the direction of force. Therefore, if the force does work in the displacement that occurred in the object, the object is always subjected to the force during the displacement, and the power is stopped when the force disappears. 3 force to do