沪科版物理选修3-4知识点（Shanghai Branch edition physics elective 3-4 knowledge points）.doc

沪科版物理选修3-4知识点（Shanghai Branch edition physics elective 3-4 knowledge points） Expressions and images of simple harmonic motion of 82. simple harmonic motion 1. Mechanical vibration: The object (or part of an object) moves back and forth on either side of a central position, called mechanical vibration. The conditions of mechanical vibration are as follows: (1) the restoring force is not zero. (2) resistance is very small. The force that makes the vibrating object return to its equilibrium position is called the restoring force, the restoring force is the effect force, and in the concrete problem, it is necessary to pay attention to the analysis of what force provides the restoring force. 2 harmonic vibration: The simplest form of vibration in a mechanical vibration. The harmonic vibration can be defined or understood in two ways: (1) the vibration of an object in direct proportion to the displacement and always pointing to the restoring force at the equilibrium position is called harmonic vibration. (2) the vibration parameters of the object, the vibration time according to sine or cosine variation, called harmonic vibration, in the high school physics teaching material is in the spring and the two pendulum special understanding and mastering the law of harmonic vibration. 3. The physical quantities of vibration are described. In addition to the physical quantities such as displacement, velocity, acceleration, kinetic energy, potential energy and so on, the new physical quantity should be introduced in order to adapt to the vibration characteristics. (1) displacement X: the directed line which is located at the position of the vibrating particle in the equilibrium position is called displacement. Displacement is a vector whose maximum is equal to its amplitude. (2) amplitude A: the maximum distance from the equilibrium position of an object that makes a mechanical vibration is called amplitude, and the amplitude is a scalar, indicating the strength of the vibration.