KS3 Cambridge Physics: Key Terms Memory Guide | KS3 剑桥物理：核心术语速记指南

📚 KS3 Cambridge Physics: Key Terms Memory Guide | KS3 剑桥物理：核心术语速记指南

Mastering physics starts with a solid grasp of key terms. This guide breaks down the essential vocabulary for KS3 Cambridge Physics, offering simple explanations and memorable tricks to help you recall each concept with ease. Whether you are learning about forces, energy or waves, these definitions and memory hacks will give you the confidence to explain ideas clearly and tackle exam questions effectively.

学好物理，从掌握核心术语开始。本指南梳理了 KS3 剑桥物理的关键词汇，提供简明解释和巧记方法，帮助你轻松记住每个概念。不管是力、能量还是波，这些定义和速记窍门都能让你清晰地解释物理现象，自信地应对考试。

1. Forces and Motion | 力与运动

Force is a push or a pull that can change an object’s speed, direction or shape. It is measured in newtons (N). A force arrow shows both magnitude and direction.

力是推或拉的作用，能改变物体的快慢、方向或形状，单位是牛顿（N）。画力箭头时要标出大小和方向。联想记忆：牛顿的苹果落下来是因为引力，所以力用“牛顿”来纪念他。

Mass is the amount of matter in an object, measured in kilograms (kg). Mass stays the same everywhere in the universe because it does not depend on gravity.

质量是物体所含物质的多少，单位千克（kg）。质量在任何地方都不变，因为它与重力无关。巧记：“质”就是“实打实”的物质量，去月球质量也不变。

Weight is the force of gravity acting on an object. It depends on mass and the strength of gravity. Weight (N) = mass (kg) × gravitational field strength (N/kg). On Earth g ≈ 10 N/kg.

重量是作用在物体上的重力。重量随重力场强度变化，公式为 W = m × g。地球上 g 约等于 10 N/kg。记忆：称重时体重秤测的是你的重量，到了月球就变轻，因为 g 变小了。

Friction is a force that opposes motion between two surfaces in contact. It can slow things down and causes wear and heat.

摩擦力是阻碍接触面相互运动的力。它会使物体减速，还会生热和磨损。词源助记：friction 和拉丁语 fricare（摩擦）同源，搓手会热就是摩擦力在起作用。

Air resistance (drag) is a type of friction that acts on objects moving through air. It increases with speed and surface area.

空气阻力也叫拖拽力，是物体在空气中运动时受到的摩擦力。速度越快、迎风面积越大，空气阻力越大。速记：打开降落伞，面积大阻力大，人就慢慢飘下。

Upthrust is an upward force exerted by a fluid (liquid or gas) on an object placed in it. If upthrust equals weight, the object floats.

浮力是流体对浸在其中物体的向上托力。浮力等于重量时物体漂浮。记忆：浴缸里的橡皮鸭被水向上托，这就是浮力。

Balanced forces occur when two or more forces acting on an object cancel each other out. The resultant force is zero, so the object stays at rest or moves at constant speed.

平衡力是作用在同一物体上的几个力互相抵消，合力为零。物体会保持静止或匀速直线运动。巧记：拔河双方势均力敌时绳子不动，就是平衡力。

Unbalanced forces produce a resultant force that is not zero. This changes an object’s speed or direction, causing acceleration, deceleration or a change in shape.

非平衡力会产生不等于零的合力，从而改变物体的快慢或方向，表现为加速、减速或形变。记忆：踢足球一瞬间，脚施加的力远大于摩擦力，球就飞出去了。

Speed is a measure of how fast something is moving, without considering direction. It is often calculated as:

speed = distance ÷ time

速率描述物体运动的快慢，不涉及方向。常用 distance ÷ time 计算。助记：看汽车仪表盘，显示的是速率，而不是速度（速度还要带上方向）。

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2. Pressure and Moments | 压强与力矩

Pressure tells us how concentrated a force is. It depends on the force applied and the area over which it acts:

pressure = force ÷ area   (p = F ÷ A)

压强表示力在单位面积上的集中程度。公式 p = F / A，单位是帕斯卡 (Pa)。巧记：图钉尖面积小，压强很大，所以容易钉入墙面；图钉帽面积大，压强小，手指就不疼。

Moment is the turning effect of a force. It depends on both the size of the force and the perpendicular distance from the pivot:

moment = force × perpendicular distance

力矩是力使物体绕支点转动的效果。力矩 = 力 × 垂直距离。单位是牛顿米 (Nm)。记忆：用扳手拧螺母，手柄越长越省力，因为垂直距离大，力矩就大。

Principle of moments states that for an object in rotational equilibrium, the total clockwise moment equals the total anticlockwise moment about the same pivot.

力矩平衡原理：当物体不发生转动时，顺时针力矩总和等于逆时针力矩总和。助记：跷跷板两端轻重相同时，力矩相等，板保持水平。

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3. Energy Stores and Transfers | 能量储存与转移

Energy is the ability to do work. It is measured in joules (J). Energy cannot be created or destroyed – it can only be transferred from one store to another.

能量是做功的本领，单位焦耳 (J)。能量既不能创造也不会消失，只能从一个储存库转移到另一个。核心口诀：能量守恒，形式在变。

Kinetic energy (KE) is the energy an object has because of its motion. KE = ½ × mass × speed². The faster or heavier an object, the more kinetic energy it stores.

动能是物体因运动而具有的能量。KE = ½mv²。物体越快、越重，动能越大。记忆：重型卡车即使速度不快，动能也非常大，刹车距离很长。

Gravitational potential energy (GPE) is the energy stored in an object due to its height above the ground. GPE = mass × g × height. Lifting an object increases its GPE.

重力势能是物体因为被举高而储存的能量。GPE = mgh。举得越高，势能越大。联想：瀑布的水从高处落下，释放重力势能带动水轮机。

Thermal energy is the internal energy stored in a substance due to the motion and arrangement of its particles. Heating increases thermal energy, and cooling reduces it.

热能（内能）是物质内部粒子运动与排列所储存的能量。加热使粒子运动加剧，热能增加。记忆：摩擦生热其实是动能转化为热能。

Chemical energy is stored in the bonds of chemical compounds. It is released during chemical reactions, for example in batteries, food and fuels.

化学能储存在化学键中。食物、电池和燃料里的化学反应会释放化学能。巧记：吃早餐补充化学能，然后转换成动能让你跑跳。

Elastic potential energy is the energy stored when an object is stretched, compressed or twisted. A stretched spring or a drawn bow stores this energy, which can be released quickly.

弹性势能是物体因被拉伸、压缩或扭转而储存的能量。拉紧的弹弓或弹簧压缩后蓄满弹性势能，一旦释放就快速转化为动能。

Energy transfer can happen by four main pathways: by forces (work done), by electric current, by heating and by radiation (light and sound waves). Understanding these pathways helps you track where energy goes.

能量转移有四种常见方式：通过力做功、电流做功、加热以及辐射（光和声波）。追踪能量去向时，记住这四条路径就不会漏掉。

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4. Work, Power and Efficiency | 功、功率与效率

Work done is the transfer of energy when a force moves an object. Work (J) = force (N) × distance moved in the direction of the force (m). If there is no movement, no work is done on that object.

功是力使物体移动时所做的能量转移。功 = 力 × 力的方向上移动的距离。如果没移动，做功为零。记忆：推墙推不动，做了很多力但功为零，因为你没有把能量转移给墙。

Power is the rate at which energy is transferred or the rate at which work is done. Power (W) = energy transferred (J) ÷ time (s). A powerful machine does the same work in less time.

功率是能量转移或做功的快慢。功率 = 能量 ÷ 时间，单位瓦特 (W)。功率越大，干同样的活越快。联想：同样搬一箱书，叉车功率远大于人力，几秒就搞定。

Efficiency measures how much of the total energy input is converted into useful energy output. It can be expressed as a decimal or percentage:

efficiency = (useful output energy ÷ total input energy) × 100%

效率表示输入总能量中有多大比例转化为有用能量。效率 = (有用输出能量 ÷ 总输入能量) × 100%。效率不会超过 100%。记忆：白炽灯大部分电能变成热而不是光，效率低；LED 灯发热少，效率高。

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5. Waves: Sound and Light | 波：声音与光

Wave is a disturbance that transfers energy from one place to another without transferring matter. Waves can be transverse or longitudinal.

波是传递能量而不传递物质的扰动。波分为横波与纵波。巧记：看球赛的人浪，人原地起坐，波形却在前进，这就是能量传递。

Amplitude is the maximum displacement of a point on a wave from its undisturbed position. In sound waves, a larger amplitude means a louder sound; in light waves, greater amplitude generally means brighter light.

振幅是波上某点离开平衡位置的最大距离。声波振幅大，声音响；光波振幅大，光更亮（简单理解）。记忆：拨吉他弦用力越大，弦偏离越远，振幅越大，声音越响。

Wavelength (λ) is the distance between two consecutive points that are in phase, e.g. crest to crest or compression to compression. It is often measured in metres.

波长 (λ) 是两个相邻且振动状态相同的点之间的距离，如波峰到波峰。单位米。联想：海面上相邻两个浪尖之间的距离就是波长。

Frequency is the number of complete waves passing a point per second. It is measured in hertz (Hz). 1 Hz = 1 wave per second. Frequency determines the pitch of a sound.

频率是每秒钟通过某点的完整波的个数，单位赫兹 (Hz)。频率决定音调高低。记忆：蚊子振翅频率高，声音尖锐；大鼓振动频率低，声音低沉。

Wave speed tells us how fast a wave travels. It is related to frequency and wavelength:

wave speed = frequency × wavelength   (v = f × λ)

波速是波传播的快慢。v = fλ。对某一介质，波速是固定的，改变频率就会改变波长。记公式：“车速 = 脚蹬频率 × 每圈走的距离”，波长好比每圈的距离。

Reflection is the bouncing back of a wave when it hits a surface it cannot pass through. The angle of incidence equals the angle of reflection.

反射是波遇到障碍物返回的现象。入射角等于反射角。生活中镜面反射和回声都是例子。速记口诀：对称反射，角角相等。

Refraction is the change in direction of a wave when it passes from one medium to another and its speed changes. Light bends towards the normal when it enters a denser medium.

折射是波越过介质交界面时因速度改变而偏折的现象。光从空气进入水中速度变慢，向法线靠近。记忆：铅笔插进水中看起来像折断了一样。

Transverse wave has vibrations perpendicular to the direction of energy transfer. Light and water waves are transverse. The wave profile shows crests and troughs.

横波振动方向与传播方向垂直。光波和水面波都是横波，有波峰和波谷。联想：上下抖绳子，波水平前行，手上下振动，这就是横波。

Longitudinal wave has vibrations parallel to the direction of energy transfer. Sound waves are longitudinal and consist of compressions and rarefactions.

纵波振动方向与传播方向平行。声波是纵波，由疏部与密部组成。巧记：用手指快速推拉弹簧，弹簧圈密一圈疏一圈向前传播，就是纵波模型。

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6. Electricity and Circuits | 电与电路

Current (I) is the flow of electric charge. In a metal wire, it is the flow of electrons. Current is measured in amperes (A) using an ammeter connected in series.

电流是电荷的定向移动，金属中即电子的流动。电流单位安培 (A)，用串联的电流表测量。水流类比：电流好比水管里水的流量。

Voltage (V) (potential difference) is the ‘push’ that drives current around a circuit. It tells us how much energy each coulomb of charge receives or transfers. Measured in volts (V).

电压（电势差）是驱动电荷流动的“推力”，表示每库仑电荷所获得或转移的能量。单位伏特 (V)。记忆：电压好比水压，水压差越大水流越急。

Resistance (R) opposes the flow of current. It is measured in ohms (Ω). A longer, thinner wire has higher resistance; a shorter, thicker wire has lower resistance.

电阻是对电流的阻碍作用，单位欧姆 (Ω)。导线越长越细，电阻越大；越短越粗，电阻越小。联想：走廊越窄，人通过越困难——电阻就是电路中的“窄通道”。

Ohm’s law links voltage, current and resistance:

voltage = current × resistance   (V = IR)

欧姆定律：V = IR。当电阻不变时，电流与电压成正比。记忆三角形：V 在上，I 和 R 在下，手盖住要求的量即可写出公式。

Series circuit has only one loop for current to flow. The current is the same everywhere, but the voltage is shared across components. If one bulb breaks, the circuit is open and all bulbs go out.

串联电路只有一条闭合路径。电流处处相等，电压分配到各元件上。一只灯泡坏了，整条路断开，所有灯泡熄灭。记忆：圣诞灯串一坏全灭，就是串联。

Parallel circuit has more than one loop. The voltage across each branch is the same as the supply voltage, but the current splits. A fault in one branch does not stop the others working.

并联电路有多条支路。各支路电压相等，总电流等于各支路电流之和。一条支路断路不影响其他支路。联想：家里的电器都并联，关掉电视不影响冰箱工作。

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7. Magnetism and Electromagnets | 磁与电磁铁

Magnetic field is the region around a magnet where magnetic materials and other magnets experience a force. Field lines go from the north pole to the south pole outside the magnet.

磁场是磁体周围能对磁性材料或其它磁体产生力的区域。磁感线从 N 极指向 S 极（体外）。记忆：撒铁屑在条形磁铁上，铁屑排成的弧线就是磁感线。

Magnetic materials are attracted to a magnet. Iron, nickel and cobalt are magnetic; steel is also magnetic because it contains iron. Non-magnetic materials, like plastic or aluminium, are not attracted.

磁性材料会被磁铁吸引，如铁、镍、钴。钢含铁所以也能被吸引。铜、铝、塑料则是非磁性材料。速记：铁钴镍三兄弟，磁铁最爱它们。

Electromagnet is a coil of wire (solenoid) with a soft iron core. When current flows, it becomes a strong magnet; when the current stops, the magnetism largely disappears. Electromagnets are used in scrapyard cranes and electric bells.

电磁铁由线圈加软铁芯构成。通电时产生强磁性，断电后磁性基本消失。应用：废铁场起重机、电铃。巧记：电磁铁“随心所欲”——通电有磁，断电无磁。

Motor effect describes the force experienced by a current-carrying wire placed in a magnetic field. This is the basis of electric motors and loudspeakers.

电动机效应：通电导线在磁场中会受到力的作用。这是电动机和扬声器的工作原理。联想：左手定则（弗莱明左手定则）可以判断力、电流和磁场方向，竖起手指就记住了。

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8. Particle Model of Matter | 物质的粒子模型

Particle model explains solids, liquids and gases in terms of tiny, moving particles. In solids, particles vibrate in fixed positions; in liquids, they slide past each other; in gases, they move rapidly in all directions.

粒子模型用微小运动的粒子解释固液气三态。固体粒子原地振动；液体粒子可滑动；气体粒子高速自由运动。记忆：学生上课—固体（在位子动），下课走动—液体，放学奔跑—气体。

Diffusion is the net movement of particles from an area of high concentration to an area of low concentration. This happens in liquids and gases; it is faster at higher temperatures because particles move faster.

扩散是粒子从高浓度区域向低浓度区域的净移动。在液体和气体中发生，温度越高扩散越快。联想：在教室一角喷香水，不久满屋飘香，就是气体扩散。

Brownian motion is the random, jerky movement of tiny visible particles (e.g. smoke particles) caused by collisions with much smaller, invisible particles of a fluid. It provides evidence for the particle model.

布朗运动是微小可见粒子（如烟雾颗粒）被更小的流体粒子碰撞后产生的无规则运动。它证明了粒子永不停息地运动。记忆：显微镜下花粉颗粒在水中乱跳，就是水分子踢的。

Gas pressure is caused by the collisions of gas particles with the walls of a container. Increasing the temperature makes particles move faster and collide more often and harder, raising the pressure. Reducing volume also increases pressure.

气体压强源于气体粒子撞击容器壁。升温会使粒子速度加快，撞击更猛更频繁，压强增大。压缩体积同样使压强上升。巧记：打气筒下压时气嘴变热，体积减小且粒子碰撞加剧。

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9. Density and States | 密度与物态

Density is the

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