Forces and Motion: A Complete IGCSE Physics Revision Guide | 力与运动：IGCSE物理完整复习指南

📚 Forces and Motion: A Complete IGCSE Physics Revision Guide | 力与运动：IGCSE物理完整复习指南

This revision guide covers the essential concepts of Forces and Motion from the Cambridge IGCSE Physics coursebook (0625 syllabus). You will learn how to distinguish scalars from vectors, interpret motion graphs, apply Newton’s laws, and solve problems involving momentum and moments. Each section pairs English explanations with Chinese translations to help you master the key ideas and exam techniques.

本复习指南涵盖剑桥IGCSE物理课程（0625考纲）中力与运动的核心考点。你将学会区分标量与矢量、解读运动图像、运用牛顿定律，并解决涉及动量和力矩的问题。每个小节均配以中英双语讲解，帮助你掌握关键概念和考试技巧。

1. Scalars and Vectors | 标量与矢量

A scalar quantity has magnitude (size) only, while a vector quantity has both magnitude and direction. This distinction is fundamental to describing motion correctly.

标量只有大小（数值），而矢量既有大小又有方向。这一区别是正确描述运动的基础。

Common scalar quantities include distance, speed, mass, time, energy, and temperature. Common vector quantities include displacement, velocity, acceleration, force, weight, and momentum. When adding vectors, you must consider direction, not just size.

常见的标量包括距离、速率、质量、时间、能量和温度。常见的矢量包括位移、速度、加速度、力、重量和动量。矢量相加时，必须考虑方向，而不仅仅是大小。

distance travelled = speed × time

路程 = 速率 × 时间

In exam questions, always check whether the problem asks for distance or displacement. A runner who completes one lap of a 400 m track has travelled a distance of 400 m but has a displacement of zero, because their final position is the same as their starting position.

在考试题目中，务必检查问题是求距离还是位移。一名跑者在400米跑道上跑完一圈，路程是400米，但位移为零，因为终点位置与起点相同。

2. Speed, Velocity and Acceleration | 速率、速度与加速度

Speed is the distance travelled per unit time and is a scalar. Velocity is the displacement per unit time and is a vector. The units for both are metres per second (m/s).

速率是单位时间内通过的路程，是标量。速度是单位时间内的位移，是矢量。两者的单位都是米每秒（m/s）。

speed = distance ÷ time | v = s/t

速率 = 路程 ÷ 时间 | v = s/t

Acceleration is the rate of change of velocity. It is a vector measured in metres per second squared (m/s²). A negative acceleration means the object is slowing down; this is also called deceleration or retardation.

加速度是速度的变化率。它是矢量，单位是米每二次方秒（m/s²）。负加速度表示物体正在减速，也称为减速度或制动减速。

acceleration = (final velocity − initial velocity) ÷ time | a = (v − u)/