小球与匀质细杆的碰撞——大学物理教学问题探讨  

ON THE TEACHING OF THE COLLISION BETWEEN A SMALL BALL AND A UNIFORM THIN ROD IN COLLEGE PHYSICS

作　　者：刘凤艳[1] 韩守振[1] 苏雪琼[1] LIU Fengyan;HAN Shouzhen;SU Xueqiong(School of Physics and Optoelectronics,Faculty of Science,Beijing University of Technology,Beijing 100124)

机构地区：[1]北京工业大学理学部物理与光电学院,北京100124

出　　处：《物理与工程》2021年第2期36-40,共5页Physics and Engineering

摘　　要：小球与细杆的碰撞问题是大学物理教学中刚体部分的一个难点问题。本文对小球与静止细杆的碰撞问题进行了分析计算,给出:通常情况下小球—细杆组成的系统所受合外力矩为零或近似为零,角动量守恒;如果细杆没有固定的光滑轴,小球与置于光滑水平面或是竖直放置的细杆碰撞时,动量或沿某一方向的动量分量守恒。如果细杆有固定光滑轴,则只有小球与细杆某一特定部位碰撞时某一方向的动量分量才有可能守恒;碰撞中如果恢复系数e≠1,动能不守恒,碰撞后小球可能继续向前运动,也可能被弹回或是停止运动。如果e=0,小球粘附于细杆之上和细杆一起绕固定轴或是小球—细杆系统的质心转动。The collision of a small ball and a uniform thin rod is a difficult topic in the rigidbody part of college physics teaching.From analysis and calculation given in this paper,the conclusion is drawn as follows.In general,the net external torque acting on the system of ball and rod is zero or approximately zero,and the total angular momentum of the system is conserved.In the case where the thin rod does not have a fixed pivot,when collision occurs between a small ball and a thin rod which is placed vertically or on a frictionless horizontal surface,the total momentum or one component of momentum is conserved.Otherwise,if the thin rod has a fixed frictionless pivot,one component of the total momentum can be conserved only when the small ball strikes the thin rod on a particular position.In the collision,if the restitution coefficient e≠1,the kinetic energy of the system is not conserved,then the small ball may keep moving forward,halt or bounce backward after the collision.If the restitution coefficient e=0,the ball will adhere to the rod,and rotate together with the rod about the fixed pivot or the center of mass of system.

关 键 词：碰撞 恢复系数 刚体 质心 

分 类 号：G642[文化科学—高等教育学] O313.3-4[文化科学—教育学]