📚 Simple Harmonic Motion for IGCSE OCR Physics | IGCSE OCR 物理：简谐运动考点精讲
Simple harmonic motion (SHM) is a fundamental type of oscillation that appears frequently in the IGCSE OCR Physics syllabus. From a swinging pendulum to a mass bobbing on a spring, SHM helps us understand how periodic motion works, and it links directly to wave behaviour. This revision guide breaks down all the key concepts, equations and graphs you need to master for your exam, with clear explanations in both English and Chinese.
简谐运动（SHM）是 IGCSE OCR 物理课程中常见的基本振动类型。从摆动的单摆到弹簧上振动的物体，简谐运动帮助我们理解周期性运动的原理，并与波的行为密切相关。本篇复习指南将用清晰的中英双语逐一解析所有关键概念、公式和图像，助你掌握考试要点。
1. What is Simple Harmonic Motion? | 什么是简谐运动？
Simple harmonic motion is defined as an oscillation in which the acceleration of the object is directly proportional to its displacement from a fixed equilibrium position and is always directed towards that equilibrium point. In other words, the further the object moves away from equilibrium, the greater the restoring force (and acceleration) that pulls it back.
简谐运动定义为物体的加速度与其偏离固定平衡位置的位移成正比，并且加速度始终指向该平衡点的一种振动。换句话说，物体离开平衡位置越远，将其拉回的回复力（以及加速度）就越大。
The condition for SHM can be written as a ∝ −x, where a is acceleration, x is displacement, and the minus sign indicates that acceleration is always opposite to displacement. This proportionality is the hallmark of a simple harmonic oscillator.
简谐运动的条件可写作 a ∝ −x，其中 a 是加速度，x 是位移，负号表示加速度始终与位移方向相反。这种比例关系是简谐振子的标志性特征。
Many real systems approximate SHM for small displacements, such as a simple pendulum swinging through a small angle or a mass on a spring moving within its elastic limit.
许多实际系统在小位移下可近似为简谐运动，例如小角度摆动的单摆或在弹性限度内振动的弹簧振子。
2. Key Terms: Amplitude, Period, Frequency | 关键术语：振幅、周期、频率
To describe SHM accurately, you need to be familiar with three essential terms:
要准确描述简谐运动，你需要熟悉三个基本术语：
- Amplitude (A) – the maximum displacement from the equilibrium position. It is measured in metres (m). | 振幅 (A) – 离开平衡位置的最大位移，单位为米 (m)。
- Period (T) – the time taken for one complete oscillation or cycle. Measured in seconds (s). | 周期 (T) – 完成一次完整振动或循环所需的时间，单位为秒 (s)。
- Frequency (f) – the number of complete oscillations per second. Measured in hertz (Hz). | 频率 (f) – 每秒钟完成的完整振动次数，单位为赫兹 (Hz)。
The relationship between period and frequency is f = 1/T and T = 1/f. These equations are useful when analysing graphs or experimental data.
周期与频率的关系为 f = 1/T 和 T = 1/f。在分析图像或实验数据时，这些公式非常实用。
In OCR IGCSE exams, you may be asked to define these terms or calculate them from given information. Always remember to include correct units.
在 OCR IGCSE 考试中，可能会要求你定义这些术语或根据给定信息进行计算。务必记住写上正确的单位。
3. Conditions for SHM: Restoring Force & Acceleration | 简谐运动的条件：回复力与加速度
For an object
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