📚 Year 12 Cambridge Physics: Key Terminology Quick Recap | 剑桥物理 Year 12 关键术语速记指南
Mastering Physics at Year 12 level is as much about speaking the language as it is about solving equations. Words like 'impulse', 'diffraction' and 'photoelectric effect' carry precise meanings that must become second nature. This revision guide breaks essential terminology into subject blocks, pairing each term with a memorable mnemonic or mental image, so you can recall definitions quickly and accurately under exam pressure.
在 Year 12 物理中，会用“行话”和会解方程一样重要。“冲量”、“衍射”、“光电效应”这些词都有精确的含义，必须变成你的第二本能。这份复习指南将核心术语按主题分块，每个词都配上好记的诀窍或画面，帮助你在考试压力下快速、准确地调取定义。
1. Kinematics: Sorted by 'SUVAT' | 运动学：SUVAT 打头阵
Kinematics comes alive with five symbols: s, u, v, a, t. Keep them straight by remembering 'SUVAT' – the name says it all. Displacement (s) is the straight‑line distance in a given direction, not to be confused with total path length (which is distance). Velocity (v) is speed with a direction; initial velocity (u) is its value at t=0. Acceleration (a) is the rate of change of velocity, measured in m s⁻². A quick memory hook: 'u' looks unfinished, so it’s the starting speed.
运动学靠五个符号说话：s, u, v, a, t。用“SUVAT”这个缩略词就能记住它们。位移 (s) 是给定方向上的直线距离，别跟总路程（distance）搞混。速度 (v) 是带方向的速率；初速度 (u) 是 t=0 时的速度。加速度 (a) 是速度的变化率，单位是 m s⁻²。小窍门：“u”看起来像个未完成的字母，恰好代表起始速度。
All four SUVAT equations stem from two simple ideas – the definition of acceleration and the area under a velocity–time graph. The equation most students forget is s = (u+v)t/2; think of it as the 'average velocity × time' recipe.
四个 SUVAT 方程其实都源于加速度的定义和速度−时间图下的面积。最容易忘的那个是 s = (u+v)t/2；把它想成“平均速度 × 时间”的配方就行了。
v = u + at | s = ut + ½at² | s = (u+v)t/2 | v² = u² + 2as
m s⁻² downward) components. Time of flight is determined entirely by the vertical motion, just like a ball thrown straight up.
处理抛体运动时，把运动拆成水平（匀速）和竖直（恒定 g=9.81 m s⁻² 向下）两个分量。飞行时间完全由竖直运动决定，就像竖直上抛一样。
2. Dynamics: Forces and Momentum in Action | 动力学：力与动量实战
Newton’s First Law is the law of inertia: an object keeps its velocity unless a net external force acts. Picture a cosmic rock drifting forever. The Second Law ip F = ma, but the more fundamental statement is net force = rate of change of momentum: Fnet = Δp/Δt. This form handles changing-mass situations, like a rocket expelling fuel.
牛顿第一定律 是惯性定律：若无净外力，物体维持原速度。想象一块永远漂流的宇宙岩石。第二定律 给出了 F = ma，但更根本的表述是 合力 = 动量变化率：Fnet = Δp/Δt。这个形式能处理变质量情形，比如火箭喷出燃料。
Momentum (p=mv) is conserved in all isolated systems. The mnemonic 'Move Only Matters' can remind you that momentum is always about mass in motion. Impulse (J) is the change in momentum, also equal to the area under a force–time graph. Imagine a 'pulse' of force—short but powerful, like a tennis racket strike. The area under that brief spike is the impulse.
动量 (p=mv) 在所有孤立系统中守恒。可以记成“动量只能是运动的质量”。冲量 (J) 是动量的变化，也等于力−时间图下的面积。想象一个力的“脉冲”——短暂却猛烈，就像网球拍的击球。那个尖峰的面积就是冲量。
When two objects collide, the type matters. Elastic collision conserves kinetic energy and momentum; inelastic collision conserves only momentum, with kinetic energy transformed to heat, sound or deformation. A useful test: if the objects stick together ('perfectly inelastic'), kinetic energy is definitely not conserved.
两物体相撞时，类型很关键。弹性碰撞 动能和动量都守恒；非弹性碰撞 只守恒动量，部分动能变成热、声音或形变。一个简便的判断：如果物体粘在一起（“完全非弹性”），动能就一定不守恒。
3. Work, Energy & Power: The Currency of Physics | 功、能与功率：物理学的“货币”
Work done (W) displacement in the direction of the force: W = F d cosθ. If you push a wall and it doesn't move, you do zero work on the wall, even if you feel tired. Kinetic energy (Ek = ½ mv²) is the energy of motion; notice the v² dependence—doubling speed quadruples the energy, which explains speed limits.
功 (W) 是力与在力的方向上的位移的乘积：W = F d cosθ。如果你推一堵墙而它纹丝不动，你对墙做的功为零，尽管你会觉得累。动能 (Ek = ½ mv²) 是运动的能量；注意到 v² 的关系——速度加倍，能量变成四倍，这也能解释限速的重要性。
Gravitational potential energy (Ep = mgh) depends only on height, not the path taken. Power (P) ing work or transferring energy: P = W/t or P = Fv for a constant force. Think of power as 'how quickly you spend the energy currency'. The unit watt (W) is just a joule per second.
重力势能 (Ep = mgh) 只取决于高度，与路径无关。功率 (P) 是做功或转移能量的速率：P = W/t，恒力时也可用 P = Fv。把功率想成“你花掉能量货币的速度”。单位瓦特 (W) 就是一焦耳每秒。
Principle of Conservation of Energy l final energy ± work done against friction. The ± sign keeps you honest about where the energy went.
能量守恒原理：能量不能凭空产生或消灭，只能转移或转化。在任何计算题中，先写出能量平衡：初始总能量 = 末了总能量 ± 克服摩擦做的功。用 ± 号能帮你老实查对能量去向。
4. Materials: Stress, Strain and Stretch | 材料：应力、应变与拉伸
Hooke’s Law says extension is proportional to load, F = kx, but only up to the limit of proportionality. Beyond that, the graph curves, though the material may still return to its original length until the elastic limit is passed. 'Hooke reminds you to keep things straight—until you overdo it.'
胡克定律 指出，在比例极限内，伸长量与载荷成正比，F = kx。超过这个点，曲线弯曲，但材料可能仍能恢复原长，直到超过了弹性极限。“胡克提醒你凡事有度，拉过头就回不来了。”
To compare materials rather than samples, we use stress (σ = F/A) and strain (ε = x/L). Young modulus E = stress/strain, a measure of stiffness. The mnemonic 'Stress is Force spread over Area' and 'Strain is the fraction you gain in length' helps separate them. Young modulus has the same units as pressure, Pa.
为了比较材料本身而不是某个样品，我们用应力 (σ = F/A) 和应变 (ε = x/L)。杨氏模量 E = 应力/应变，是刚度的量度。可记成“应力是力摊在面积上”，“应变是伸长占原长的分数”。杨氏模量的单位和压强一样，是帕斯卡 (Pa)。
A material with a large Young modulus (e.g., steel) is stiff and stretches little under load; a small Young modulus (e.g., rubber) means it is compliant. Ductile materials draw into wires (copper), brittle tic deformation (glass). Words to lock in: Ductile = drawn out; Brittle = breaks abruptly.
杨氏模量大的材料（如钢）刚且受力时伸长小；杨氏模量小的材料（如橡胶）柔顺。延性材料能拉成丝（铜），脆性材料几乎不发生塑性形变就断裂（玻璃）。记忆窍门：Ductile 和 “拉长” 联想；Brittle 和 “崩裂” 联想。
5. Waves: From Ripples to Rays | 波：从涟漪到射线
Transverse waves have vibrations perpendicular to the direction of energy travel (light, water ripples). Longitudinal waves vibrate parallel (sound, seismic P‑waves). Picture a stadium wave (transverse) versus a spring you push and pull (longitudinal).
横波的振动方向与能量传播方向垂直（光、水波）；纵波的振动平行（声波、地震P波）。想象足球场人浪（横波）和推拉弹簧（纵波）。
The fundamental glossary: frequency (f, Hz) and period (T, s) are reciprocals, f = 1/T. Wavelength (λ) tween successive points in phase. The wave speed equation v = f λ holds for all waves. The phase difference between two points is given in radians or degrees; a whole cycle is 2π rad. If two points are separated by half a wavelength, the phase difference is π rad (180°) and they are in antiphase.
基本词汇：频率 (f, Hz) 和周期 (T, s) 互为倒数，f = 1/T。波长 (λ) 是相继同相位点之间的距离。波速公式 v = f λ 对所有波都成立。两点之间的相位差用弧度或度表示；一个完整周期是 2π 弧度。若两点相距半个波长，相位差为 π rad (180°)，二者反相。
Diffraction is the spreading of waves around an obstacle or through a gap; it is most noticeable when the gap size is comparable to λ. Interference pose: constructive where path difference = nλ, destructive where path difference = (n+½)λ. Stationary waves store energy, with nodes (zero displacement) and antinodes (max displacement).
衍射是波遇到障碍物或通过狭缝时的展宽现象；当缝宽与波长相近时最明显。干涉是两列相干波叠加的结果：波程差 = nλ 时加强，波程差 = (n+½)λ 时减弱。驻波储存能量，有波节（位移为零）和波腹（位移最大）。
Polarisation is the proof that a wave is transverse; only transverse waves can be polarised. A polarising filter transmits only the component of the wave vibrating in one plane, reducing intensity without changing frequency.
偏振是横波的独家证据；只有横波才能偏振。偏振片只允许在单一平面内振动的分量通过，会降低光强但不改变频率。
6. Electricity: The Flow that Drives Circuits | 电学：驱动电路的流动
Electric current (I) . Think of water current: the number of litres flowing per second is analogous to coulombs per second. Potential difference (V) is the energy transferred per unit charge: V = W/Q. It’s the 'push' that drives current, like water pressure. Resistance (R = V/I) is the opposition to current; it converts electrical energy into heat.
电流 (I) 是电荷流动的速率：I = ΔQ/Δt。想一想水流：每秒流过多少升，就类似每秒流过多少库仑。电势差 (V) 是每单位电荷转移的能量：V = W/Q，是驱动电流的“推力”，好比水压。电阻 (R = V/I) 是对电流的阻碍，把电能转化成热。
Ohm’s Law states that, for a metallic conductor at constant temperature, V ∝ I, so R is constant. The resistance of a wire is given by resistivity ρ s on material and temperature, not shape. A short, thick, copper wire has tiny resistance.
欧姆定律 指出，对温度恒定的金属导体，V ∝ I，因此 R 是常数。一根导线的电阻由电阻率 ρ 决定：R = ρL/A。电阻率取决于材料和温度，与形状无关。短、粗的铜线电阻就极小。
Electrical power se P = I²R for power dissipated as heat in a resistor (Joule heating). A helpful reminder: 'Power is the product of push (V) and flow (I).'
电功率 可写成 P = IV, P = I²R 或 P = V²/R。计算电阻发热时用 P = I²R（焦耳热）。记住：“功率是推力 (V) 与流量 (I) 的乘积。”
7. DC Circuits: Divider Rules and Hidden Resistances | 直流电路：分压规则与隐藏电阻
Kirchhoff’s First Law (junction rule) sums currents to zero: ΣIin = ΣIout. It’s just charge conservation—charge doesn’t pile up at a junction. Kirchhoff’s Second Law ule) says around any closed loop, ΣV = 0. The sum of the emfs equals the sum of the p.d.s.
基尔霍夫第一定律（节点定律）是电流的代数和为零：ΣI入 = ΣI出。这不过是电荷守恒——节点处不会堆积电荷。基尔霍夫第二定律（回路定律）是对任一闭合回路，ΣV = 0。电动势之和等于各元件电势差之和。
Potential divider: two resistors in series divide the supply voltage in proportion to their resistances. The output voltage Vout = [R2/(R1+R2)] × Vin. Imagine a see‑saw: the bigger the resistance R2, the larger its share of the voltage.
电势分压器：两个电阻串联时，按阻值比例瓜分电源电压。输出电压 Vout = [R2/(R1+R2)] × Vin。想象一个跷跷板：R2 阻值越大，它分到的电压就越高。
Electromotive force (emf, ε) is the energy supplied per unit charge by a source, measured in volts. The terminal p.d. is less than emf when current flows because of internal resistance (r): Vterminal = ε − Ir. Picture r as a tiny resistor inside the battery that always steals some energy.
电动势 (emf, ε) 是电源每单位电荷提供的能量，单位也是伏特。当有电流时，由于内阻 (r)，路端电压会低于电动势：V端 = ε − Ir。把 r 想象成电池内部一个会偷走能量的小电阻。
8. Quantum Physics: Packets of Light and Matter Waves | 量子物理：光包与物质波
The photoelectric effect demonstrates light’s particle nature. Each photon onstant. When a photon strikes a metal surface, an electron is ejected only if hf ≥ Φ, the work function—the minimum energy to liberate an electron. The threshold frequency f₀ = Φ/h is the minimum frequency for emission.
光电效应 揭示了光的粒子性。每个光子携带能量 E = hf，h 是普朗克常数。光子打到金属表面，只有 hf ≥ Φ 时才能敲出电子，Φ 是逸出功——释放一个电子的最小能量。截止频率 f₀ = Φ/h，是能发生发射的最低频率。
Maximum kinetic energy of photoelectrons is Ek,max = hf − Φ. The stopping potential Vs is the voltage needed to just stop the fastest electrons: eVs = Ek,max. Mnemonic: 'Photon gives energy, metal takes its due (Φ), the rest is kinetic.'
光电子的最大动能 为 Ek,max = hf − Φ。止动电压 Vs 是恰好阻止最快电子所需的电压：eVs = Ek,max。口诀：“光子给能量，金属扣掉‘入场费’（Φ），剩下的变成动能。”
Wave–particle duality extends to matter: the de Broglie wavelength tron diffraction through a crystalline lattice proves electrons behave as waves. Remember: 'If it has momentum, it has a wavelength—even a football, though its λ is too tiny to notice.'
波粒二象性 也适用于实物粒子：德布罗意波长 λ = h/p，p 为动量。电子穿过晶格发生衍射，证实了电子的波动性。记住：“只要有动量，就有波长——连足球也有，只是它的波长小到察觉不到。”
9. Particle & Nuclear Physics: A Zoo of Hadrons and Leptons | 粒子与原子核物理：强子与轻子的动物园
All matter is made of quarks and leptons, the true elementary particles. Hadrons feel the strong nuclear force and are composed of quarks. Baryons (proton, neutron) contain three quarks; mesons (pion, kaon) are quark–antiquark pairs. Think 'Baryon = three (like
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