📚 Year 12 WJEC Physics: Vocabulary & Terminology Quick Revision Guide | Year 12 WJEC 物理：词汇术语速记指南
Mastering the essential vocabulary and terminology is half the battle in Year 12 WJEC Physics. This quick revision guide breaks down key terms unit by unit, pairing clear English definitions with concise Chinese explanations, and includes equations directly from the specification. Use it to reinforce your memory before tests.
掌握基本词汇和术语是 Year 12 WJEC 物理考试成功的一半。这份速记指南按单元分解关键术语，将清晰的英文定义与简明的中文解释配对，并包含考纲中的方程式。用它来在考试前强化记忆。
1. Kinematics and Motion | 运动学
Scalar: A physical quantity that has magnitude only. Example: distance, speed, mass, time.
标量：只有大小没有方向的物理量。例如：路程、速率、质量、时间。
Vector: A physical quantity that has both magnitude and direction. Example: displacement, velocity, acceleration, force.
矢量：既有大小又有方向的物理量。例如：位移、速度、加速度、力。
Distance: The total length of the path travelled by an object, a scalar quantity.
路程：物体运动轨迹的总长度，是标量。
Displacement: The shortest straight-line distance from the initial to the final position, with direction. It is a vector.
位移：从初位置到末位置的有向直线距离，是矢量。
Speed: The rate of change of distance; scalar. Average speed = total distance / total time.
速率：路程随时间的变化率，标量。平均速率 = 总路程 / 总时间。
Velocity: The rate of change of displacement; vector. v = Δs / Δt. Its direction is the same as the displacement.
速度：位移随时间的变化率，矢量。v = Δs / Δt。方向与位移方向相同。
Acceleration: The rate of change of velocity; vector. a = Δv / Δt. It can be positive (speeding up) or negative (slowing down, sometimes called deceleration).
加速度：速度的变化率，矢量。a = Δv / Δt。可以是正（加速）或负（减速，有时称为减速度）。
The equations of uniformly accelerated motion (suvat) are:
匀加速运动方程组（suvat）如下：
v = u + at s = ut + ½at² v² = u² + 2as s = ½(u + v)t
2. Forces and Newton’s Laws | 力与牛顿定律
Force: A push or pull that can change the motion of an object; measured in newtons (N). It is a vector.
力：能改变物体运动状态的推或拉；单位是牛顿（N）。它是矢量。
Mass: The amount of matter in an object; a scalar, measured in kilograms (kg). Mass does not change with location.
质量：物体所含物质的多少；标量，单位是千克（kg）。质量不随位置改变。
Weight: The gravitational force on a mass; W = mg, where g ≈ 9.81 m s⁻² on Earth. It is a vector directed towards the centre of the Earth.
重力：作用在物体上的引力；W = mg，地球表面 g ≈ 9.81 m s⁻²。它是矢量，方向指向地心。
Newton’s First Law: An object remains at rest or in uniform motion unless acted on by a resultant force. (Inertia)
牛顿第一定律：若合外力为零，物体将保持静止或匀速直线运动状态。（惯性定律）
Newton’s Second Law: The resultant force on an object is directly proportional to its rate of change of momentum. For constant mass: F = ma.
牛顿第二定律：物体所受的合外力正比于其动量的变化率。当质量不变时：F = ma。
Newton’s Third Law: When two objects interact, they exert equal and opposite forces on each other. These forces act on different bodies.
牛顿第三定律：两物体相互作用时，它们受到大小相等、方向相反的力。这两个力作用在不同物体上。
Friction: A force that opposes the relative motion of two surfaces in contact. It can be static or dynamic.
摩擦力：阻碍接触面相对运动的力，分为静摩擦和动摩擦。
Normal reaction: The support force exerted by a surface perpendicular to itself on an object resting on it.
支持力（法向反作用力）：接触面对其上的物体施加的垂直于接触面的力。
3. Energy, Work and Power | 能量、功和功率
Work done: Energy transferred when a force moves an object. W = Fs cos θ, where θ is the angle between force and displacement. Measured in joules (J).
功：力使物体移动时传递的能量。W = Fs cos θ，θ 为力与位移的夹角。单位是焦耳（J）。
Gravitational potential energy (GPE): Energy of an object due to its height in a gravitational field. ΔEₚ = mgh, where h is vertical height.
重力势能：物体因在重力场中的高度而具有的能量。ΔEₚ = mgh，h 是竖直高度。
Kinetic energy (KE): Energy of an object due to its motion. Eₖ = ½mv².
动能：物体因运动而具有的能量。Eₖ = ½mv²。
Conservation of energy: Energy cannot be created or destroyed, only transferred into different forms. In an isolated system, total energy remains constant.
能量守恒：能量既不能凭空产生，也不能凭空消失，只能从一种形式转化为其他形式。孤立系统的总能量不变。
Power: The rate of doing work or transferring energy. P = W / t or P = Fv. Unit: watt (W).
功率：做功或能量转化的快慢。P = W / t 或 P = Fv。单位：瓦特（W）。
Efficiency: Ratio of useful energy output to total energy input, usually expressed as a percentage. Efficiency = (useful work out / work in) × 100%.
效率：有用输出能量与输入总能量之比，通常用百分比表示。效率 = (有用功 / 做功) × 100%。
4. Momentum and Impulse | 动量与冲量
Momentum: Product of mass and velocity. p = mv. It is a vector quantity; its direction is the same as velocity. Unit: kg m s⁻¹.
动量：质量与速度的乘积。p = mv。它是矢量，方向与速度同向。单位：kg m s⁻¹。
Impulse: Change in momentum due to a force acting over a time interval. Impulse = FΔt = Δp = mv – mu. Unit: N s or kg m s⁻¹.
冲量：力在一段时间内累积效应引起的动量变化量。冲量 = FΔt = Δp = mv – mu。单位：N s 或 kg m s⁻¹。
Conservation of momentum: In a closed system with no external forces, total momentum before an interaction equals total momentum after. Useful in collisions and explosions.
动量守恒：在无外力的封闭系统中，相互作用前的总动量等于相互作用后的总动量。用于碰撞和爆炸等问题。
Elastic collision: A collision where both kinetic energy and momentum are conserved. Objects bounce apart without energy loss to heat or deformation.
弹性碰撞：动量和动能都守恒的碰撞。物体弹开而不将能量损失为热或形变。
Inelastic collision: A collision where momentum is conserved but kinetic energy is not; some kinetic energy is converted to other forms. Perfectly inelastic if objects stick together.
非弹性碰撞：动量守恒但动能不守恒的碰撞；部分动能转化为其他形式的能量。完全非弹性碰撞中物体粘合在一起。
5. Materials and Young Modulus | 材料与杨氏模量
Tensile stress: The force applied per unit cross-sectional area. σ = F / A. Unit: pascal (Pa) or N m⁻².
拉伸应力：单位横截面积上所受到的力。σ = F / A。单位：帕斯卡（Pa）或 N m⁻²。
Tensile strain: The extension per unit original length. ε = ΔL / L₀. It has no units (dimensionless).
拉伸应变：单位原始长度的伸长量。ε = ΔL / L₀。无量纲。
Young modulus: A measure of stiffness of a solid material. E = σ / ε = (F/A) / (ΔL/L₀). Unit: Pa. A larger Young modulus means less extensible.
杨氏模量：衡量固体材料刚度的物理量。E = σ / ε = (F/A) / (ΔL/L₀)。单位：Pa。模量越大材料越难以拉伸。
Elastic limit: The maximum stress that can be applied so that the material returns to its original length when the stress is removed. Beyond this, plastic deformation occurs.
弹性极限：材料能恢复原长的最大应力。超过此极限将发生塑性形变。
Plastic deformation: Permanent change in shape that remains after the applied stress is removed. Caused by atomic layers sliding past each other.
塑性形变：应力撤除后不能恢复的永久形变，原因在于原子层的滑移。
Brittle: A material that fractures with little or no plastic deformation, e.g. glass, cast iron.
脆性：材料在断裂前几乎没有塑性形变，例如玻璃、铸铁。
Ductile: A material that can experience large plastic deformation before breaking; can be drawn into wires, e.g. copper.
延性：材料在断裂前能承受较大的塑性形变，可拉成丝，例如铜。
6. Waves and Wave Properties | 波及其性质
Wave: A disturbance that transfers energy without transferring matter. Mechanical waves need a medium; electromagnetic waves do not.
波：传递能量而不传递物质的扰动。机械波需要介质；电磁波不需要。
Transverse wave: A wave in which particle oscillations are perpendicular to the direction of energy transfer, e.g. light waves, water ripples.
横波：质点振动方向与能量传播方向垂直，例如光波、水面波纹。
Longitudinal wave: A wave in which particle oscillations are parallel to the direction of energy transfer, e.g. sound waves. Shows compressions and rarefactions.
纵波：质点振动方向与能量传播方向平行，例如声波。表现为疏密波。
Amplitude (A): The maximum displacement from the equilibrium position. For a transverse wave, it is the height of a crest or depth of a trough.
振幅（A）：质点离开平衡位置的最大位移。对横波而言是波峰的高度或波谷的深度。
Wavelength (λ): The shortest distance between two successive points in phase (e.g. crest to crest). Unit: metre (m).
波长（λ）：两个相邻同相位点（如波峰到波峰）之间的最短距离。单位：米（m）。
Frequency (f): The number of complete cycles per second. Unit: hertz (Hz). f = 1 / T.
频率（f）：单位时间内完成的完整振动次数。单位：赫兹（Hz）。f = 1 / T。
Period (T): The time taken for one complete oscillation. T = 1 / f. Unit: second (s).
周期（T）：完成一次全振动所需的时间。T = 1 / f。单位：秒（s）。
Wave speed (v): The speed at which energy is transferred. v = fλ. For a given medium, speed is constant unless the medium changes.
波速（v）：能量传播的速度。v = fλ。在给定介质中波速恒定，除非介质改变。
v = fλ T = 1 / f
7. Interference and Diffraction | 干涉与衍射
Principle of superposition: When two or more waves meet, the resultant displacement is the vector sum of individual displacements.
叠加原理：两列或更多列波相遇时，合成位移为各列波的位移矢量和。
Constructive interference: Occurs when waves arrive in phase (path difference =
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