KS3 CAIE Physics: Key Topics Overview | KS3 CAIE 物理：核心知识点梳理

📚 KS3 CAIE Physics: Key Topics Overview | KS3 CAIE 物理：核心知识点梳理

KS3 CAIE Physics forms part of the Cambridge Lower Secondary Science curriculum, covering Stages 7 to 9 (typically ages 11–14). It introduces fundamental principles of forces, energy, waves, electricity, magnetism, pressure, moments and space. A solid grasp of these topics builds a strong foundation for IGCSE Physics and beyond.

KS3 CAIE 物理是剑桥初中科学课程的一部分，涵盖第 7 至第 9 阶段（通常为 11–14 岁）。它介绍了力、能量、波、电学、磁学、压强、力矩和空间等基本原理。扎实掌握这些主题为 IGCSE 物理及更高阶段的学习奠定坚实基础。

---

1. Forces and Motion | 力与运动

Forces are pushes or pulls that can change the speed, direction or shape of an object. They are measured in newtons (N).

力是推或拉，可以改变物体的速度、方向或形状。力的单位是牛顿 (N)。

When several forces act on an object, we find the resultant force. If forces are balanced, the object remains at rest or moves at a constant speed. If unbalanced, the object accelerates or decelerates.

当多个力作用在物体上时，我们需要求出合力。如果力平衡，物体保持静止或匀速直线运动；如果力不平衡，物体会加速或减速。

Friction is a force that opposes motion. Air resistance is a type of friction that acts on objects moving through air. Both can be reduced by streamlining.

摩擦力是一种阻碍运动的力。空气阻力是物体在空气中运动时受到的摩擦力。两者都可以通过流线型设计来减小。

Speed is the distance travelled per unit time. The equation for constant speed is:

速度是单位时间内通过的路程。匀速运动的公式为：

speed = distance ÷ time

A distance–time graph shows how distance changes with time. A steeper slope means a higher speed. A horizontal line means the object is stationary.

距离‑时间图显示距离随时间的变化。斜率越大，速度越大。水平线表示物体静止。

---

2. Mass, Weight and Gravity | 质量、重量与重力

Mass is the amount of matter in an object, measured in kilograms (kg). It does not change with location.

质量是物体所含物质的多少，单位是千克 (kg)。质量不随位置改变。

Weight is the force of gravity acting on an object, measured in newtons (N). It depends on the gravitational field strength (g). On Earth, g ≈ 10 N/kg.

重量是作用在物体上的重力，单位是牛顿 (N)。它取决于引力场强度 (g)。在地球表面，g 约等于 10 N/kg。

weight = mass × gravitational field strength (W = m × g)

Gravity is a non-contact force that attracts all objects with mass. The Moon’s gravity is weaker, so your weight would be less there, but your mass stays the same.

重力是一种非接触力，吸引所有具有质量的物体。月球的引力较小，所以在那里你的重量会变小，但质量不变。

---

3. Energy and Work | 能量与功

Energy is the ability to do work and is measured in joules (J). Energy can be stored in different ways: kinetic (movement), thermal (heat), chemical (fuels, food), gravitational potential (height), elastic potential (stretched or compressed), and nuclear.

能量是做功的能力，单位是焦耳 (J)。能量可以以不同形式储存：动能（运动）、热能（热量）、化学能（燃料、食物）、重力势能（高度）、弹性势能（拉伸或压缩）和核能。

Energy can be transferred from one store to another by forces (mechanical work), heating, or by waves (light, sound). The total energy in a closed system is always conserved.

能量可以通过力（机械功）、加热或波（光、声）从一个储存转移到另一个。在封闭系统中，总能量始终守恒。

Work is done when a force moves an object. The work done is equal to the energy transferred.

当力使物体移动时，就做了功。所做的功等于转移的能量。

work done = force × distance moved in direction of force (W = F × d)

For example, lifting a book does work against gravity and increases its gravitational potential energy store.

例如，举起书本克服重力做了功，增加了书的重力势能储存。

---

4. Thermal Physics | 热物理

Thermal energy transfer occurs by conduction, convection and radiation. Conduction happens mainly in solids when vibrating particles pass on energy.

热能传递通过传导、对流和辐射进行。传导主要发生在固体中，通过振动粒子的能量传递。

Convection occurs in fluids (liquids and gases) where warmer, less dense regions rise and cooler, denser regions sink, forming a convection current.

对流发生在流体（液体和气体）中，较热、密度较小的区域上升，较冷、密度较大的区域下沉，形成对流循环。

Radiation is the transfer of energy by infrared electromagnetic waves and does not require a medium. Shiny, light surfaces are poor emitters and absorbers of radiation, while dark, matt surfaces are good emitters and absorbers.

辐射是通过红外电磁波传递能量，不需要介质。光亮、浅色的表面是辐射的不良发射体和吸收体，而黑暗、粗糙的表面是良好发射体和吸收体。

Conductors like metals allow heat to flow quickly; insulators like plastics and wood reduce heat transfer.

导体如金属让热量快速传递；绝缘体如塑料和木材减少热传递。

---

5. Sound Waves | 声波

Sound travels as longitudinal waves, where particles vibrate back and forth in the same direction as the wave travels. Sound requires a medium (solid, liquid or gas) to travel through; it cannot travel through a vacuum.

声音以纵波形式传播，粒子沿波传播的方向前后振动。声音需要介质（固体、液体或气体）才能传播；它不能在真空中传播。

The speed of sound varies: it is fastest in solids, slower in liquids and slowest in gases. An echo is a reflected sound wave.

声速在不同介质中不同：固体中最快，液体中较慢，气体中最慢。回声是反射的声波。

Pitch is related to frequency (number of vibrations per second, measured in hertz, Hz). A higher frequency gives a higher pitch. Loudness depends on the amplitude of the wave; a larger amplitude means a louder sound.

音调与频率（每秒振动次数，单位赫兹 Hz）有关。频率越高，音调越高。响度取决于波幅；振幅越大，声音越响。

---

6. Light and Optics | 光与光学

Light travels in straight lines and at a very high speed (3 × 10⁸ m/s in a vacuum). Shadows form when light is blocked by an opaque object.

光沿直线传播，速度极快（真空中 3 × 10⁸ m/s）。当光被不透明物体阻挡时，就会形成影子。

The law of reflection states that the angle of incidence equals the angle of reflection, measured from the normal.

反射定律指出，入射角等于反射角，均从法线测量。

Refraction is the bending of light as it passes from one medium to another due to a change in speed. This is why a straw appears bent in water.

折射是光因速度变化在进入不同介质时发生的弯曲。这就是吸管在水中看起来弯折的原因。

White light can be split into a spectrum of colours (red, orange, yellow, green, blue, indigo, violet) by a prism. This is called dispersion. We see coloured objects because they reflect only certain colours of light.

白光可以通过棱镜分解成光谱（红、橙、黄、绿、蓝、靛、紫），这称为色散。我们看到有颜色的物体，是因为它们只反射特定颜色的光。

---

7. Electricity and Circuits | 电学与电路

An electric circuit needs a complete loop for current to flow. Components include cells, batteries, wires, lamps, switches, resistors and buzzers. Standard circuit symbols are used to represent them.

电路需要完整的回路才能有电流流过。元件包括电池、电池组、导线、灯泡、开关、电阻器和蜂鸣器。用标准电路符号来表示它们。

Current is the flow of electric charge, measured in amperes (A). In a series circuit, the current is the same everywhere. In a parallel circuit, the current splits at junctions.

电流是电荷的流动，单位是安培 (A)。在串联电路中，各处电流相等。在并联电路中，电流在分支点分流。

Voltage

Published by TutorHao | KS3 Physics Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）