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碰撞是力学问题中一类很典型的物理模型,由于要综合运用动量、能量知识,致使许多学生在解这类问题时有无从下手之感,或者考虑不全面导致解题出错。其实,只要审清题意,建立起正确的碰撞模型,然后抓住模型的特征,运用有关的物理规律即可求解。那么,碰撞模型具有哪些特征呢?1.动量守恒——发生碰撞的物体系在碰撞过程中,由于作用时间很短,相互作用力很大,系统所受的外力一般可忽略,动量守恒。2.动能不增——碰撞过程中一般均要出现发声、发热、粘在一起、裂成碎块及发生永久形变等现象,因此,实际的碰撞中,碰撞后系统的总动能不可能大于碰撞前系统的总动能,对于弹性碰撞,只是系统内物体间动能相互转移,没有转化为其它形式的能,故碰撞前后系统的总动能守恒,但系统的动能损失也不是没有限
Collision is a very typical physical model in mechanics problems. Due to the comprehensive use of momentum and energy knowledge, many students feel uncomfortable in solving such problems, or they may not fully solve the problem. In fact, as long as the questions are cleared and the correct collision model is established, then the characteristics of the model are grasped and the relevant physical laws can be used to solve the problem. Then, what are the characteristics of the collision model? 1. Momentum conservation - the collision of the object system in the collision process, due to the short interaction time, the interaction force is very large, the external force of the system is generally negligible, momentum conservation. 2. The kinetic energy does not increase - In the process of collision, vocalization, fever, sticking together, splitting into fragments, and permanent deformation occur. Therefore, in the actual collision, the total kinetic energy of the system after collision cannot be greater than the impact. The total kinetic energy of the front system, for elastic collisions, is only the transfer of kinetic energy among objects within the system, and does not translate into other forms of energy. Therefore, the total kinetic energy of the system before and after the collision is conserved, but the kinetic energy loss of the system is not unlimited.