📚 Year 12 Cambridge Engineering: Vocabulary and Terminology Quick Memory Guide | Year 12 剑桥工程：词汇术语速记指南
Understanding technical vocabulary is half the battle in engineering exams. This guide compiles over 50 essential terms for the Cambridge International AS Level Engineering syllabus (9706). Each entry includes a clear definition, typical units, and a memory cue to help you internalise concepts fast. Studying the terms topic by topic will strengthen your written answers and design analysis.
理解专业词汇是工程考试成功的一半。本指南汇编了剑桥国际AS Level工程教学大纲(9706)中的50多个核心术语。每个词条都包含清晰的定义、常用单位和记忆线索，助你快速内化概念。按主题逐组学习这些术语，将提升你的书面表达和设计分析能力。
1. Fundamental Quantities and Units | 基本量和单位
Force (F): A push or pull acting on an object, measured in newtons (N). Newton's second law: F = m x a. Always consider direction – force is a vector.
力 (F): 作用于物体的推或拉，单位为牛顿(N)。牛顿第二定律: F = m x a。力是矢量，始终要考虑方向。
Mass (m): The amount of matter in a body, measured in kilograms (kg). Mass does not change with location; it is a scalar quantity.
质量 (m): 物体所含物质的多少，单位为千克(kg)。质量不随位置改变，是标量。
Weight (W): The gravitational force on a mass, W = m x g, unit newton (N). Weight varies with gravitational field strength; on Earth g ≈ 9.81 m/s².
重量 (W): 质量所受的重力，W = m x g，单位牛顿(N)。重量随重力场强度变化；地球表面g约9.81 m/s²。
Work (W): Energy transferred when a force moves an object through a distance in the direction of the force. W = F x d x cosθ, unit joule (J). No movement in the force's direction means zero work done.
功 (W): 力使物体沿力的方向移动时传递的能量。W = F x d x cosθ，单位焦耳(J)。在力的方向上没有位移则做功为零。
Power (P): The rate of doing work or transferring energy. P = W / t = ΔE / t, unit watt (W). Think of power as 'how quickly energy is spent'.
功率 (P): 做功或传递能量的速率。P = W / t = ΔE / t，单位瓦特(W)。可以将功率想象为“能量消耗的快慢”。
Pressure (p): Force applied perpendicular to a surface per unit area. p = F / A, unit pascal (Pa) or N/m². A sharp knife creates high pressure due to small area.
压强 (p): 垂直作用于单位面积上的力。p = F / A，单位帕斯卡(Pa)或 N/m²。锋利的刀因面积小而产生大压强。
2. Mechanics of Materials | 材料力学
Stress (σ): Internal force per unit area within a material, measured in pascals (Pa) or megapascals (MPa). σ = F / A. Stress is the intensity of internal load.
应力 (σ): 材料内部单位面积上的内力，单位为帕斯卡(Pa)或兆帕(MPa)。σ = F / A。应力表示内力的密集程度。
Strain (ε): Extension per unit original length – a dimensionless ratio. ε = ΔL / L₀. Strain is often expressed as a percentage.
应变 (ε): 单位原始长度的伸长量，无量纲比值。ε = ΔL / L₀。应变常以百分数表示。
Young's modulus (E): A measure of a material's stiffness, defined as stress divided by strain in the linear elastic region. E = σ / ε, unit pascal (Pa). High E means the material resists deformation.
杨氏模量 (E): 衡量材料刚度的指标，定义为线弹性范围内应力与应变之比。E = σ / ε，单位帕斯卡(Pa)。高E值表示材料抵抗变形能力强。
Yield strength: The stress at which a material begins to deform plastically. Beyond this point, permanent deformation occurs. Often used as a design limit.
屈服强度: 材料开始发生塑性变形时的应力。超过该点即产生永久变形。常用作设计限制值。
Ultimate tensile strength (UTS): The maximum stress a material can withstand while being stretched before necking and fracture. Point '3' on the stress-strain curve.
极限抗拉强度 (UTS): 材料在拉伸时发生颈缩和断裂前所能承受的最大应力。应力-应变曲线上的最高点。
Ductility: The ability of a material to undergo significant plastic deformation before rupture, e.g. copper and mild steel. Measured by percentage elongation or reduction in area.
延展性: 材料在断裂前承受显著塑性变形的能力，如铜和低碳钢。通过伸长率或断面收缩率衡量。
Brittleness: The tendency of a material to fracture with little or no plastic deformation, e.g. glass and cast iron. Brittle materials absorb low energy during impact.
脆性: 材料几乎没有塑性变形就断裂的倾向，如玻璃和铸铁。脆性材料在冲击时吸收的能量很低。
Poisson's ratio (ν): The ratio of lateral strain to axial strain within the elastic range. ν = - (ε lateral / ε axial). Most engineering metals have ν around 0.3.
泊松比 (ν): 弹性范围内横向应变与轴向应变之比。ν = - (ε 横向 / ε 轴向)。多数工程金属的泊松比约为0.3。
3. Statics and Structures | 静力学与结构
Equilibrium he resultant force and resultant moment on a body are both zero. For static equilibrium, ΣF = 0 and ΣM = 0.
平衡: 物体所受合力和合力矩均为零的状态。对于静力平衡，ΣF = 0 且 ΣM = 0。
Resultant force: The single force that has the same effect as all the forces acting on a body combined. Found by vector addition.
合力: 与作用在物体上的所有力组合效果相同的单个力。通过矢量加法求得。
Free-body diagram (FBD): A simplified sketch showing all external forces and moments acting on a body, with the body isolated from its surroundings. Essential for resolving forces.
受力图 (FBD): 将物体与其周围隔离，展示所有外力和外力矩的简化简图。是分解力的必备工具。
Moment of a force (M): The turning effect of a force about a point. M = F x d, where d is the perpendicular distance from the pivot to the line of action. Unit: newton-metre (N·m).
力矩 (M): 力对某点的转动效应。M = F x d，其中d是支点到力作用线的垂直距离。单位：牛顿·米 (N·m)。
Couple: A pair of equal, opposite, parallel forces that produce rotation but no net translational force. The moment of a couple is F x perpendicular distance between forces.
力偶: 一对大小相等、方向相反、作用线平行的力，只产生转动而不产生净平移力。力偶矩 = 力 x 力之间的垂直距离。
Shear force: The internal force acting parallel to the cross-section of a beam. Shear force diagrams help locate points of maximum shear stress.
剪力: 平行于梁横截面作用的内力。剪力图帮助确定最大剪应力位置。
Bending moment: The internal moment that causes a beam to bend. It is calculated at a section and varies along the beam length. Positive bending moment typically causes sagging.
弯矩: 使梁发生弯曲的内力矩。按截面计算，并沿梁长变化。正弯矩通常导致下凹弯曲。
4. Dynamics and Motion | 动力学与运动
Velocity (v): Rate of change of displacement; a vector quantity. v = Δs / Δt, unit m/s. Speed is its scalar magnitude.
速度 (v): 位移的变化率；矢量。v = Δs / Δt，单位 m/s。速率是其标量大小。
Acceleration (a): Rate of change of velocity. a = Δv / Δt, unit m/s². It can be positive (speeding up) or negative (deceleration).
加速度 (a): 速度的变化率。a = Δv / Δt，单位 m/s²。可为正值（加速）或负值（减速）。
Momentum (p): Product of mass and velocity, p = m x v, unit kg·m/s. Momentum is conserved in closed systems without external forces.
动量 (p): 质量与速度的乘积，p = m x v，单位 kg·m/s。封闭无外力系统中动量守恒。
Impulse: Change in momentum caused by a force acting over a time interval. Impulse = F Δt = Δp. Used in crash safety design.
冲量: 力在一段时间内作用导致的动量变化。冲量 = F Δt = Δp。用于碰撞安全设计。
Newton's first law: A body stays at rest or in uniform motion unless acted upon by a resultant external force. Inertia is the resistance to change in motion.
牛顿第一定律: 若无净外力作用，物体保持静止或匀速直线运动。惯性是抵抗运动变化的性质。
Friction (f): A force that opposes relative motion between surfaces in contact. f ≤ μN, where μ is the coefficient of friction and N the normal reaction.
摩擦力 (f): 阻碍接触表面相对运动的力。f ≤ μN，μ为摩擦系数，N为法向反力。
Coefficient of friction (μ): The ratio of limiting friction to normal reaction. It depends on material pair and surface finish. Static μ is usually larger than kinetic μ.
摩擦系数 (μ): 极限摩擦力与法向反力之比。取决于材料配对和表面光洁度。静摩擦系数通常大于动摩擦系数。
5. Energy and Thermodynamics | 能量与热力学
Internal energy (U): Sum of all microscopic kinetic and potential energies of the particles in a substance. It changes with temperature and phase.
内能 (U): 物质内部所有粒子微观动能与势能的总和。随温度和相态变化。
Heat (Q): Energy transferred due to a temperature difference. Measured in joules (J). Heat flows from hot to cold spontaneously.
热量 (Q): 因温度差而传递的能量，单位焦耳(J)。热量自发地从高温传向低温。
Specific heat capacity (c): The energy required to raise the temperature of 1 kg of a substance by 1°C (or 1 K). Q = m c ΔT, unit J/(kg·K).
比热容 (c): 使1 kg物质温度升高1°C（或1 K）所需的能量。Q = m c ΔT，单位 J/(kg·K)。
Latent heat (L): Energy absorbed or released during a phase change at constant temperature. Q = m L, with specific latent heat of fusion (melting) or vaporisation (boiling).
潜热 (L): 在恒温相变过程中吸收或释放的能量。Q = m L，分为熔化潜热和汽化潜热。
First law of thermodynamics: Energy cannot be created or destroyed, only transferred or converted. ΔU = Q - W, where W is work done by the system.
热力学第一定律: 能量不能被创造或消灭，只能传递或转化。ΔU = Q - W，
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