📚 Cambridge IGCSE Physics: Key Concepts Explained | 剑桥IGCSE物理：核心概念解析
Mastering IGCSE Physics requires a firm grasp of its core concepts, from scalars and vectors to waves, electricity, and the fundamentals of space physics. This revision guide breaks down each key topic with clear explanations in both English and Chinese, helping you build confidence for your exams.
掌握IGCSE物理需要扎实理解其核心概念，从标量与矢量到波、电学以及空间物理基础。本复习指南用清晰的中英双语解释逐一分解每个关键主题，帮助你建立考试信心。
1. Scalars and Vectors | 标量与矢量
In physics, all measurable quantities are classified as either scalars or vectors. Scalars have only magnitude, described by a number and a unit. Common scalars include distance, speed, mass, time, energy and temperature. Scalar addition follows ordinary arithmetic.
在物理学中，所有可测量的量被分为标量或矢量。标量只有大小，用一个数字和单位描述。常见的标量包括距离、速率、质量、时间、能量和温度。标量的相加遵循普通算术。
Vectors have both magnitude and direction. Displacement, velocity, acceleration, force, weight and momentum are vector quantities. When adding vectors, direction must be considered. You can use graphical methods such as the tip-to-tail method or the parallelogram of forces to find the resultant.
矢量既有大小又有方向。位移、速度、加速度、力、重量和动量都是矢量。相加矢量时必须考虑方向。你可以使用图解法，如首尾相接法或力的平行四边形法则来求合力。
2. Motion Graphs | 运动图像
t is stationary; a straight sloping line indicates constant speed. The gradient of the line gives the speed: speed = Δdistance / Δtime.
距离-时间图和速度-时间图提供了运动的可视化描述。在距离-时间图中，一条水平直线表示物体静止；一条倾斜直线表示匀速运动。线的斜率给出速度：速度 = Δ距离 / Δ时间。
he acceleration: a = (v - u)/t. The area under the line represents the distance travelled.
在速度-时间图上，水平线表示匀速，而斜线表示加速或减速。斜率给出加速度：a = (v - u)/t。线下的面积代表所经过的距离。
3. Newton's Laws of Motion | 牛顿运动定律
Newton's First Law states that an object remains at rest or in uniform motion in a straight line unless acted upon by a resultant force. This property is called inertia. The larger the mass, the greater the inertia.
牛顿第一定律指出，除非受到合外力作用，物体将保持静止或沿直线匀速运动状态。这种性质叫做惯性。质量越大，惯性越大。
Newton' iven mass, acceleration is directly proportional to the resultant force. Force is measured in newtons (N).
牛顿第二定律将合外力、质量和加速度联系起来：F = ma。对于给定质量，加速度与合外力成正比。力以牛顿 (N) 为单位测量。
Newton's Third Law states that for every action force there is an equal and opposite reaction force. These forces act on different bodies and are of the same type.
牛顿第三定律指出，每个作用力都有一个大小相等、方向相反的反作用力。这些力作用在不同的物体上，且是同一类型的力。
4. Free Fall and Terminal Velocity | 自由落体与终端速度
² on Earth. In the absence of air resistance, all objects fall with the same acceleration regardless of mass.
当物体仅受重力下落时，它以自由落体加速度向下加速，地球上g ≈ 9.8 m/s²。在没有空气阻力的情况下，所有物体无论质量大小都以相同的加速度下落。
In real situations, air resistance opposes motion. As speed increases, air resistance grows until it balances the weight. At this point, the resultant force becomes zero, and the object falls at a constant terminal velocity.
在实际情形中，空气阻力阻碍运动。随着速度增加，空气阻力增大直到与重量平衡。此时合外力为零，物体以恒定的终端速度下落。
5. Energy, Work and Power | 能量、功与功率
Energy is the ability to do work and is conserved in any process. The main forms include kinetic energy (½mv²), gravitational potential energy (mgh), thermal, chemical and nuclear energy. Energy can be transferred between stores.
能量是做功的能力，在任何过程中守恒。主要形式包括动能 (½mv²)、重力势能 (mgh)、热能、化学能和核能。能量可以在储存库之间转移。 Published by TutorHao | Physics Revision Series | aleveler.com
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