📚 Pre-U Cambridge Physics: Vocabulary & Terminology Quick Revision Guide | Pre-U Cambridge 物理：词汇术语速记指南
Mastering physics terminology is the foundation for success in the Cambridge Pre-U Physics examination. This revision guide gathers the most essential terms across the syllabus and provides straightforward memory aids. Each term is defined clearly in English and immediately followed by a Chinese explanation to bridge language gaps and deepen understanding. Use this as your quick glossary and mental checklist during final revision.
掌握物理术语是通过剑桥 Pre-U 物理考试的基石。这份速记指南汇集了教学大纲中最核心的术语，并给出了简洁的记忆技巧。每个术语先用英文定义，紧接着给出中文解释，以消除语言障碍、加深理解。把它当作你冲刺复习时的快速术语表和思维清单。
1. Kinematics & Dynamics | 运动学与动力学
Displacement (s): The shortest distance in a specific direction from the initial to the final position; it is a vector. Mnemonic: 'Displacement' contains 'place' – you change place with a direction. Contrast with distance, a scalar.
位移：从初位置到末位置的有向直线距离，是矢量。记忆：位置发生了移动，不但有大小还要有方向。与标量“路程”区分。
Velocity (v): Rate of change of displacement. It is a vector; a change in direction means velocity changes even if speed is constant.
速度：位移的变化率，是矢量。即使速率不变，只要方向改变，速度就发生变化。
Acceleration (a): Rate of change of velocity. It is a vector and can result from a change in speed, direction, or both.
加速度：速度的变化率，是矢量。可以由速度大小或方向的变化引起。
SUVAT equations: For uniform acceleration along a straight line:
v = u + at
s = ut + ½at²
v² = u² + 2as
s = ½(u + v)t
s = vt − ½at². The five linked variables are s, u, v, a, t.
匀加速运动方程：五个相互关联的物理量 s, u, v, a, t 之间的关系式。记忆口诀：“初速末速时间找，位移加速都有了”。
Newton's laws of motion: 1st Law – mains at rest or in uniform motion unless acted on by a resultant force (inertia). 2nd Law – Net force = mass × acceleration (F = ma). 3rd Law – For every action there is an equal and opposite reaction.
牛顿运动定律：第一定律（惯性定律）— 无合力则静者恒静、动者匀速；第二定律 F = ma；第三定律 — 作用力与反作用力大小相等、方向相反，作用在不同物体上。
Momentum A vector quantity; conserved in an isolated system when no external resultant force acts. Impulse = change in momentum Δp = FΔt, equal to the area under a force-time graph.
动量 p = mv，是矢量；在无外合力作用的孤立系统中守恒。冲量 等于动量的变化 Δp = FΔt，也等于力–时间图线下的面积。
2. Energy, Work & Power | 能量、功与功率
Work done etween force and displacement. Measured in joules (J); work transfers energy mechanically.
功：W = F s cosθ，θ 是力与位移的夹角，单位焦耳(J)。功是能量传递的一种量度。
Kinetic energy (KE = ½mv²): Energy due to motion. Gravitational potential energy (GPE = mgh) near the Earth's surface.
动能 KE = ½mv²，由运动而具有的能量。重力势能 在地表附近为 mgh。
Principle of conservation of energy: Energy cannot be created or destroyed, only transferred or transformed.
能量守恒定律：能量不会凭空产生或消失，只能转移或转化为其他形式。
Power ate of doing work. Unit: watt (W). In a uniform motion, power equals force times velocity.
功率：做功的快慢，P = W/t = Fv，单位瓦特(W)。
Efficiency: Ratio of useful output power (or energy) to total input power. Often expressed as a percentage. Never greater than 100%.
效率：有用输出功率(或能量)与总输入之比，常用百分比表示，永远不大于100%。
3. Circular Motion & Gravitational Fields | 圆周运动与引力场
Angular velocity (ω): ω = Δθ/Δt, unit rad s⁻¹. It links linear speed and radius: v = ωr.
角速度 ω：角位移随时间的变化率，单位弧度每秒(rad s⁻¹)，关系式 v = ωr。
Centripetal acceleration (a): a = v²/r = ω²r, always directed towards the centre. Centripetal force F = mv²/r = mω²r.
向心加速度 a = v²/r = ω²r，始终指向圆心。向心力 F = mv²/r = mω²r。
Newton's law of gravitation GMm/r². The force is attractive and acts along the line joining the centres of two masses.
万有引力定律：F = GMm/r²，引力沿两物体质心连线，且总是吸引力。
Gravitational field strength (g): g = F/m, equals acceleration of free fall. Near a spherical mass, g = GM/r².
引力场强度 g = F/m，等于自由落体加速度。球对称天体附近 g = GM/r²。
Gravitational potential always negative; work done per unit mass to bring a test mass from infinity to that point.
引力势 V = -GM/r，永远为负值；把单位质量从无限远处移至该点外力所做的功。
4. Materials & Mechanics of Solids | 材料与固体力学
Hooke's law : Extension is proportional to applied force up to the limit of proportionality: F = kx, where k is the spring constant.
胡克定律：在比例极限内，伸长量与外力成正比：F = kx，k 为劲度系数。
Stress (σ = F/A): Force per unit cross-sectional area, unit Pa. Strain (ε = ΔL/L₀): Extension per unit original length, dimensionless.
应力 σ = F/A，单位帕斯卡(Pa)。应变 ε = ΔL/L₀，无量纲。
Young modulus measure of stiffness; the gradient of the initial linear portion of a stress-strain graph.
杨氏模量 E = 应力/应变，衡量材料刚度的物理量，等于应力–应变曲线起始线性段的斜率。
Elastic limit: The maximum stress a material can withstand and still return to its original length when unloaded. Beyond it, plastic deformation occurs.
弹性极限：撤去外力后能恢复原长的最大应力；超过后将发生塑性形变。
Ductile materials can undergo large plastic deformation before fracture (e.g., copper). Brittle materials fracture with little plastic deformation (e.g., glass).
延性材料 在断裂前能产生较大塑性形变(如铜)；脆性材料 几乎不经历塑性形变就断裂(如玻璃)。
5. Waves & Optics | 波动与光学
Transverse wave: Oscillations perpendicular to the direction of energy transfer (e.g., light, water waves). Longitudinal wave: Oscillations parallel to energy transfer (e.g., sound).
横波：振动方向与能量传播方向垂直(如光波)；纵波：振动方向平行于传播方向(如声波)。
Wave parameters second), period T = 1/f, wavelength λ (distance between two consecutive in-phase points).
波的基本参量：振幅 A(最大位移)、频率 f(每秒完整振动的次数)、周期 T = 1/f、波长 λ(相邻同相点之间的距离)。
Wave speed: v = fλ. In a given medium, speed depends on the medium's properties, not on frequency.
波速 v = fλ，在同一介质中波速与介质性质有关，与频率无关。
Phase difference: Measure of how 'out of step' two oscillations are; expressed in radians or degrees. Coherence requires constant phase difference.
相位差：两个振动之间的步调差异，以弧度或角度表示。相干波要求相位差恒定。
Superposition principle: When two waves meet, the total displacement is the vector sum of the individual displacements. Constructive interference occurs when path difference = nλ; destructive interference when path difference = (n+½)λ.
叠加原理：两列波相遇时，合位移等于各波位移的矢量和。相长干涉条件：波程差为波长的整数倍；相消干涉条件：波程差为半波长的奇数倍。
Diffraction: Spreading of waves around obstacles or through gaps; most noticeable when the gap size is comparable to λ.
衍射：波遇障碍物或通过狭缝时偏离直线传播的现象，缝宽与波长相近时最明显。
6. Oscillations & SHM | 振动与简谐运动
Simple harmonic motion (SHM) equilibrium and directed towards it: a = −ω²x. The solution is x = A cos(ωt) or A sin(ωt).
简谐运动：加速度与离开平衡位置的位移成正比、方向相反：a = −ω²x。位移方程 x = A cos(ωt) 或 A sin(ωt)。
Period T: Mass-spring system T = 2π√m/k. Simple pendulum (small amplitude) T = 2π√l/g. Frequency f = 1/T.
周期：弹簧振子 T = 2π√m/k；单摆(小角度) T = 2π√l/g。频率 f = 1/T。
Energy in SHM al : Total mechanical energy = ½mω²A². Energy continuously converts between kinetic and potential.
简谐运动中的能量：总机械能 = ½mω²A²，动能与势能相互转化但总和不变(无阻尼时)。
Damping: Loss of energy due to resistive forces; light damping reduces amplitude gradually, critical damping returns to equilibrium fastest without oscillating, heavy damping returns slowly.
阻尼：因阻力引起的能量损失。弱阻尼振幅逐渐减小；临界阻尼最快回到平衡位置且不振荡；过阻尼返回缓慢。
Resonance: When driving frequency equals natural frequency, amplitude becomes maximum. Sharp resonance indicates low damping.
共振：驱动力频率等于系统固有频率时振幅达到最大。尖锐的共振峰表示阻尼较小。
7. Electric Circuits & Components | 电路与元件
Electric charge = ΔQ/Δt, unit ampere (A). Direction of conventional current is opposite to electron flow.
电荷 Q，单位库仑(C)。电流 I = ΔQ/Δt，单位安培(A)。规定正电荷移动方向为电流方向。
Potential difference (V = W/Q): Energy transferred per unit charge between two points. Unit volt (V). Resistance R = V/I, unit ohm (Ω).
电势差(电压) V = W/Q，单位伏特(V)。电阻 R = V/I，单位欧姆(Ω)。
Ohm's law: For an ohmic conductor at constant temperature, current is proportional to potential difference, so R is constant.
欧姆定律：对于欧姆导体，在温度不变时电流与电压成正比，电阻恒定。
Electromotive force (EMF, ε): The energy supplied by a source per unit charge. Terminal p
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