📚 Year 9 CAIE Physics: Vocabulary & Terminology Quick-Memorisation Guide | 初三 CAIE 物理：词汇术语速记指南
Mastering the Year 9 CAIE Physics course begins with understanding the language of the subject. This guide provides a topic-by-topic breakdown of essential vocabulary, each paired with a clear definition, a bilingual explanation, and a memory tip. Use these pages to build your physics lexicon quickly and with confidence.
掌握初三 CAIE 物理课程，首先要理解这门学科的语言。本指南按主题梳理核心词汇，每个术语都配有清晰的定义、中英双语解释和记忆技巧。用这些页面快速、自信地构建你的物理词汇库。
1. Kinematics: Motion Terms | 运动学术语
Kinematics describes how objects move without worrying about what causes the motion. The four fundamental terms you must know are speed, velocity, acceleration, and displacement. Knowing the difference between scalar and vector quantities is the key to using them correctly.
运动学描述物体的运动，而不关心引起运动的原因。你必须掌握的四个基本术语是速率、速度、加速度和位移。区分标量和矢量是正确使用它们的关键。
| Term | English Definition | 中文定义 | Memory Tip |
|---|---|---|---|
| Speed | Rate of change of distance; scalar. | 距离的变化率；标量。 | Speedometer shows magnitude only – no direction. |
| Velocity | Speed in a stated direction; vector. | 带方向的速度；矢量。 | Velocity has direction – imagine an arrow. |
| Acceleration | Rate of change of velocity; vector. | 速度的变化率；矢量。 | Speeding up, slowing down, or changing direction. |
| Displacement | Shortest straight-line distance from start to finish with direction; vector. | 从起点到终点的最短直线距离，带方向；矢量。 | 'Displace' = move out of place; always a direct path. |
To tell scalars from vectors, think: 'Scalar = Scale (magnitude only), Vector has a 'V' pointing to a direction.' ment are vectors. Acceleration is always a vector because it measures how velocity changes – if you turn a corner at constant speed, you still accelerate!
区分标量和矢量可以这样想：“标量只有大小（scale），矢量（vector）里有个‘矢’，像箭头一样指向某个方向。”速率和路程是标量；速度和位移是矢量。加速度总是矢量，因为它衡量速度的变化——如果你以恒定速率转弯，你仍然有加速度！
The equation for acceleration is central to kinematics. Remember it as the 'change in velocity' formula.
加速度公式是运动学的核心。把它记为‘速度变化’公式。
a = (v – u) / t
where u is initial velocity, v is final velocity, and t is time taken. The same idea works with symbols: a = Δv / Δt.
其中 u 是初速度，v 是末速度，t 是时间。同理也可用符号表示为：a = Δv / Δt。
2. Forces and Newton's Laws | 力与牛顿定律
Forces are pushes or pulls that can change an object's shape or motion. The SI unit is the newton (N). Mass and weight are often confused, but in physics they are completely different concepts. Newton's three laws summarise how forces affect every object in the universe.
力是能改变物体形状或运动的推或拉。它的国际单位是牛顿（N）。质量和重量经常被混淆，但在物理中它们是完全不同的概念。牛顿三大定律概括了力如何影响宇宙中的每一个物体。
| Term | English Definition | 中文定义 | Memory Tip |
|---|---|---|---|
| Force | A push or pull; measured in newtons (N). | 推或拉；以牛顿（N）为单位。 | F = ma – force causes acceleration. |
| Mass | Amount of matter in an object; scalar, unit kg. | 物体所含物质的多少；标量，单位千克。 | Mass never changes – same on Earth or Moon. |
| Weight | Force due to gravity; vector, unit N. W = mg. | 由于引力产生的力；矢量，单位牛顿。W = mg。 | Weight changes with gravity; on Moon g = 1.6 N/kg. |
| Resultant force | The single force that has the same effect as all forces acting; determines acceleration. | 合力：与所有作用力效果相同的单一力，决定加速度。 | Add forces in same direction, subtract opposite ones. |
| Friction | Force opposing motion between two surfaces in contact. | 两个接触面之间阻碍运动的力。 | Rough surfaces = more friction; always slows things down. |
Newton' ves with constant velocity unless a resultant force acts on it. Think of a book on a table – it won't slide unless you push it. Newton' w: F = m × a. The bigger the force, the greater the acceleration for the same mass. Newton' tion force. When you push a wall, the wall pushes you back with exactly the same strength.
牛顿第一定律（惯性）：物体保持静止或匀速直线运动状态，直到有力迫使它改变。想一想桌上的书——除非你推它，否则它不会滑动。牛顿第二定律：F = m × a。质量相同时，力越大，加速度越大。牛顿第三定律：每个作用力都有一个大小相等、方向相反的反作用力。你推墙时，墙也会用同样大小的力回推你。
Many students confuse mass and weight. Mass is the amount of 'stuff' and is measured in kilograms; it is a universal property. Weight f about 50 N. Carry a simple mental picture: a kilogram of apples on Earth still has the same mass on the Moon, but it weighs only a sixth as much.
很多学生混淆质量和重量。质量是物质的量，以千克为单位，是一个普遍属性。重量是质量所受的引力，以牛顿为单位。在地球上，g ≈ 10 牛/千克，所以一个5千克的物体重量约50牛。记住一个简单的画面：一千克苹果在地球上和在月球上有相同的质量，但在月球上重量只有地球的六分之一。
3. Energy Types and Transfers | 能量类型与转化
Energy is the ability to do work. It can be stored (potential) or moving (kinetic). The principle of conservation of energy says that energy cannot be created or destroyed, only transferred from one form to another. Efficiency tells us how much of the input energy ends up doing useful work.
能量是做功的能力。它可以被储存（势能）或运动（动能）。能量守恒定律指出，能量既不会凭空产生也不会凭空消失，只会从一种形式转化为另一种形式。效率告诉我们有多少输入的能量最终完成了有用的工作。
| Term | English Definition | 中文定义 | Memory Tip |
|---|---|---|---|
| Kinetic energy | Energy of motion; KE = ½mv². | 运动的能量；KE = ½mv²。 | K for 'kinesis' – movement. |
| Gravitational potential energy | Energy stored due to height; GPE = mgh. | 由于高度而储存的能量；GPE = mgh。 | 'Potential' = has the potential to fall. |
| Thermal energy | Total kinetic energy of particles in a substance. | 物质中所有粒子动能的总和。 | Hotter = particles vibrate faster. |
| Work done | Energy transferred when a force moves an object; W = Fd. | 力使物体移动时转移的能量；W = Fd。 | Work = force × distance moved in direction of force. |
| Efficiency | Ratio of useful output energy to total input energy; can be expressed as a percentage. | 有用输出能量与总输入能量的比值；可用百分比表示。 | Efficiency = useful / total; always ≤ 1 (or 100%). |
Use energy song mnemonics: 'Half m v squared is KE, m g h gives you GPE.' Energy transfers can be shown with Sankey diagrams – e more energy. Efficiency = useful power output ÷ total power input. No machine can be 100% efficient because of friction and heat losses.
用顺口溜记忆：“½ m v² 是动能，m g h 是重力势能。”能量转化可以用桑基图表示——箭头越宽代表能量越多。效率 = 有用的输出功率 ÷ 总输入功率。由于摩擦和热量损失，没有机器能达到100%的效率。
4. Waves: Properties and Types | 波：性质与类型
Waves transfer energy from one place to another without transferring matter. All waves have amplitude, wavelength, frequency, and speed. There are two main families: transverse waves (oscillations perpendicular to direction of travel, e.g. light, water ripples) and longitudinal waves (oscillations parallel to direction, e.g. sound).
波将能量从一个地方传递到另一个地方而不传递物质。所有的波都有振幅、波长、频率和速度。主要有两类：横波（振动方向垂直于传播方向，例如光波、水波）和纵波（振动方向平行于传播方向，例如声波）。
| Term | English Definition | 中文定义 | Memory Tip |
|---|---|---|---|
| Amplitude | Maximum displacement from the rest position; relates to energy. | 偏离平衡位置的最大位移；与能量有关。 | Loudness of sound, brightness of light. |
| Wavelength (λ) | Distance between two consecutive crests or compressions. | 相邻两个波峰（或相邻两个密部）之间的距离。 | One full cycle of the wave. |
| Frequency (f) | Number of complete waves passing a point per second; unit hertz (Hz). | 每秒通过某点的完整波的数量；单位赫兹（Hz）。 | High f = high pitch sound. |
| Wave speed | How fast the wave travels; v = f λ. | 波传播的快慢；v = f λ。 | Speed = frequency × wavelength. |
The universal wave equation v = f λ ured in metres, frequency in hertz, and speed in m/s. For sound in air, speed is about 330–340 m/s. Light is much faster: 3 × 10⁸ m/s.
通用的波动方程 v = f λ 把三个量联系在一起。波长通常以米为单位，频率以赫兹为单位，波速以米/秒为单位。声波在空气中的速度大约为330–340米/秒。光速则快得多：3 × 10⁸ 米/秒。
A clever way to remember the two wave types: 'Transverse – like a Tsunami crossing the sea, particles go Up and down; Longitudinal – Like pushing a slinky spring, particles go back and forth along the line.' Sound is longitudinal: imagine vibrating air molecules bunching together (compressions) and spreading apart (rarefactions).
一个巧记两种波型的方法：“横波——想象海上飞跃的海豚（transverse），质点上下振动；纵波——像推动弹簧（longitudinal），质点沿直线前后振动。”声音是纵波：想象振动的空气分子一会拥挤在一起（密部），一会又散开（疏部）。
5. Electricity: Current, Voltage, Resistance | 电：电流、电压、电阻
Electric circuits are built around three core ideas: charge moving (current), energy per charge (voltage), and opposition to flow (resistance). Understanding the water-pipe analogy makes these abstract concepts concrete.
电路建立在三个核心概念上：电荷的移动（电流）、每单位电荷的能量（电压）和对流动的阻碍（电阻）。理解水管类比能让这些抽象概念变得具体。
| Term | English Definition | 中文定义 | Memory Tip |
|---|---|---|---|
| Current (I) | Rate of flow of electric charge; unit ampere (A). | 电荷流动的速率；单位安培（A）。 | Water flow rate in a pipe. |
| Voltage (V) | Energy transferred per unit charge; unit volt (V). Also called potential difference. | 每单位电荷转移的能量；单位伏特（V）。又称电势差。 | Water pressure pushing charge. |
| Resistance (R) | Opposition to current; unit ohm (Ω). | 对电流的阻碍；单位欧姆（Ω）。 | Narrow pipe – harder to push water through. |
| Ohm's law | V = I × R for a resistor at constant temperature. | 在恒定温度下，电阻两端 V = I × R。 | VIR – Very Important Rule. |
The water analogy: voltage is like the water pressure from a pump, current is the flow rate of water through the hose, and resistance is any kink or narrowing in the hose. Increase the pressure (voltage) and more water flows; add a narrow section (resistance) and the flow drops. This helps you picture series and parallel circuits: series is one loop, so the same current passes through each component; parallel provides separate branches, so the current splits.
水管类比：电压就像水泵提供的压强，电流就像水管中的水流速率，电阻就像水管中的堵塞或变窄。增大压强（电压），水流增加；加入窄段（电阻），水流降低。这能帮助你理解串联和并联电路：串联是一条回路，所以各处电流相同；并联提供独立支路，所以电流会分流。
Ohm's law is the central equation for circuits. The formula triangles help: cover the quantity you want to find.
欧姆定律是电路的核心方程。公式三角有帮助：遮住你想求的量。
V = I × R
When V is in volts, I in amperes, and R in ohms, the relationship is linear for a fixed resistor.
当 V 以伏特为单位、I 以安培为单位、R 以欧姆为单位时，对于固定电阻，关系是线性的。
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