对滑轮悬挂物体问题利用角动量定理和刚体定轴转动定律的分析

Analysis on Quesitions of Pulley Hanging Objects Using Theory of Angular Momentum and Newton's Second Law for Rotation

角动量定理与刚体定轴转动定律的运用是学生学习“大学物理”课程时的重难点.虽然角动量定理与刚体定轴转动定律都可以处理物体转动问题,但是在具体分析时所体现的物理机制是不同的.以滑轮悬挂物体这一类问题为例,针对如何应用角动量定理或刚体定轴转动定律进行了详细的分析.通过分析发现,滑轮悬挂物体这一类问题具有一定的特殊性,利用这种特殊性能够简化解题过程.但是在教学过程中必须强调这种特殊性的起因,以帮助学生正确理解相关物理概念.

The theory of angular momen tum and Newton's second law for rotation are the major difficulties for students learning college physics.Although they all can be used in solving the rotation pro blem involved in physics,the corresponding mechanisms reflected in the specific analysis are different.Taking the problem of a mass hangs on a pulley as an example,this study provides a detailed analysis about the application of the theory of an gular momentum or Newton's second law for rotation.Our analysis demonstrates that the problem of a mass hangs on a pulley has some characteristics which could be used to simplify the solving process.Nevertheless,the causes of these characteristics must be em phasized during the teaching process in order to help the students correctly understand the basic concepts in physics.