单摆在振动中的受力分析

Analysis of the Received Forces of a simple Pendulum during Oscillation

关于单摆在振动中所受的力.常出现一些模糊认识,即认为单摆在振动中所受的回复力就是摆球所受重力与绳子拉力的合力,显然,这是错误的.实际上单摆在振动中所受的回复力只是合力的切向分力.除此之外,摆球还受到合力的法向分力的作用.那么单摆在振动过程中,切向力、法向力及合力的大小和方向是否在变化?怎样变化?弄清这个问题,对澄清上述模糊认识是有帮助的.本文试对这个问题从定性、定量两方面加以讨论.

Some vague understandings are always appeared when considering the recived forces of a simple pendulum during oscillation. To state the restoring force of a simple pendulum during oscillation is the resultant force of the gravity of the ball and the pulling force of the thread is wrong . In fact, the restoring force received during oscillation of a simple pendulum is the resultant force of the tangential component and the normal component force. Do the tangential force, the mormal force, the resultant force and their directions during oscillation of a simple pendulum change? How do they change to get an correct answer of these questions is very helpful to clarify the above mentioned vague understandings. This paper intends to discuss these questions in quality and quantity.