📚 Core Knowledge Review for Year 10 Cambridge Physics | Year 10 剑桥物理核心知识点梳理
Welcome to this bilingual core-knowledge review for Year 10 Cambridge Physics. It gathers the essential ideas of mechanics, thermal physics, waves, electricity, magnetism and atomic physics into twelve linked sections, each pairing a clear English explanation with its Chinese counterpart. Definitions, units, formulae, graphs and experimental ideas are all covered, so the article works both as a first-time study guide and as a rapid revision sheet before school tests or the IGCSE examinations.
欢迎阅读这篇 Year 10 剑桥物理核心知识点双语梳理。本文把力学、热学、波动、电学、磁学与原子物理的核心内容整理成十二个相互衔接的小节，每一节都用英文讲解紧跟中文对照。定义、单位、公式、图像与实验要点都有覆盖，既适合初次系统学习，也适合校内测验或 IGCSE 考试前的快速复习。
1. Describing Motion | 描述运动
÷ t. The SI unit is metres per second (m/s). A car covering 120 m in 6 s has an average speed of 20 m/s. Average speed uses total distance over total time, whereas instantaneous speed is the reading on a speedometer at one moment; on a distance-time graph, instantaneous speed is the gradient of the tangent.
速率是标量，衡量物体运动的快慢，由路程除以时间计算：v = d ÷ t。国际单位是米/秒（m/s）。一辆车 6 s 内行驶 120 m，平均速率为 20 m/s。平均速率用总路程除以总时间，而瞬时速率是某一时刻速度表的读数；在路程-时间图上，瞬时速率等于切线的斜率。
v = d ÷ t average speed = total distance ÷ total time
Velocity is a vector; it includes direction. Displacement is the vector equivalent of distance, so it records how far an object ends up from its starting point in a stated direction. An object moving with constant speed but changing direction, such as a runner on a circular track, has a changing velocity even though its speed is steady. Vector quantities such as force, velocity and acceleration must be added with direction in mind, while scalars such as mass, time and energy are added arithmetically.
速度是矢量，包含方向。位移是与距离对应的矢量，记录物体相对出发点最终移动了多远以及方向。若物体速率不变但方向改变，例如沿圆形跑道奔跑的运动员，其速度仍在改变，尽管速率不变。力、速度、加速度等矢量相加时必须考虑方向，而质量、时间、能量等标量按普通算术相加即可。
2. Acceleration and Motion Graphs | 加速度与运动图像
nitial velocity and v the final velocity. The SI unit is metres per second squared (m/s²). A positive acceleration means speeding up in the chosen positive direction; a negative acceleration, often called deceleration, means slowing down. Free fall near the Earth' surface gives a constant acceleration of about 9.8 m/s² when air resistance is negligible.
加速度是速度的变化率：a = (v − u) ÷ t，其中 u 是初速度，v 是末速度。国际单位是米/秒²（m/s²）。正加速度表示沿所选正方向加速，负加速度通常称为减速度，表示减速。在地球表面附近自由下落时，若空气阻力可忽略，加速度恒为约 9.8 m/s²。
a = (v − u) ÷ t and for uniform acceleration: s = u t + ½ a t²
Motion graphs carry a great deal of examinable information. On a distance-time graph, the gradient gives speed and a horizontal line means the object is stationary. On a velocity-time graph, the gradient gives acceleration and the area under the line gives the distance travelled; a horizontal line means constant velocity, and a straight sloping line means uniform acceleration.
运动图像承载了大量考点。在路程-时间图上，斜率表示速率，水平线段表示物体静止。在速度-时间图上，斜率表示加速度，图线下的面积表示行驶的路程；水平线段表示匀速运动，倾斜的直线段表示匀加速运动。
- Distance-time graph: gradient = speed | 路程-时间图：斜率 = 速率
- Velocity-time graph: gradient = acceleration, area = distance | 速度-时间图：斜率 = 加速度，面积 = 路程
- Curved line on a distance-time graph = changing speed | 路程-时间图的曲线表示速率在变化
3. Forces and Newton's Laws | 力与牛顿运动定律
A force is a push or a pull that can change an object's shape, speed or direction. Force is measured in newtons (N) with a newton meter, and it is a vector. Several forces acting on a body can be combined into a single resultant force; if the resultant is zero the forces are balanced and the object's motion does not change. Friction, air resistance, tension, upthrust and normal contact force are all examples of forces to recognise and label on diagrams.
力是能改变物体形状、速率或方向的推或拉。力用牛顿（N）作单位，用弹簧测力计测量，并且是矢量。作用在同一物体上的几个力可以合成为一个合力；若合力为零，则受力平衡，物体的运动状态不变。摩擦力、空气阻力、张力、浮力和支持力都是需要在受力图中识别并标注的力。
g, where g ≈ 9.8 N/kg on Earth. A 5 kg bag has a mass of 5 kg everywhere but weighs about 49 N on Earth and only about 8 N on the Moon. Hooke' force, F = k x, up to the limit of proportionality, where k is the spring constant in N/m.
质量是物体所含物质的多少，用千克测量，不随位置变化。重力是地球对该质量的引力：W = m g，地球表面 g ≈ 9.8 N/kg。一个 5 kg 的包在哪儿质量都是 5 kg，但在地球上重约 49 N，在月球上只重约 8 N。胡克定律指出，在比例极限内，弹簧的伸长量与所加拉力成正比：F = k x，其中 k 是劲度系数，单位 N/m。
Newton' t stays at rest or moves at constant velocity unless acted on by a resultant force. Newton's second law links force, mass and acceleration: F = m a. Newton' en drag equals weight, so the resultant force becomes zero and acceleration falls to zero.
牛顿第一定律指出，物体在不受合力作用时保持静止或匀速直线运动。牛顿第二定律把力、质量和加速度联系起来：F = m a。牛顿第三定律指出，若 A 对 B 施力，B 必对 A 施加大小相等、方向相反的力。当阻力等于重力时达到终端速度，此时合力为零，加速度降为零。
4. Moments, Work, Energy and Power | 力矩、功、能量与功率
icular distance from the pivot, measured in newton metres (N m). The principle of moments states that for a body in equilibrium, the sum of clockwise moments about a point equals the sum of anticlockwise moments. A see-saw balances when the heavier child sits closer to the pivot, which is why a small force at a large distance can balance a large force at a small distance.
力矩衡量力的转动效果：力矩 = 力 × 到支点的垂直距离，单位是牛顿米（N m）。力矩平衡原理指出，处于平衡状态的物体，绕某点的顺时针力矩之和等于逆时针力矩之和。跷跷板平衡时较重的小孩坐得更靠近支点，这正是小力配上较长的力臂可以平衡大力配上较短的力臂的原因。
The centre of gravity is the point through which the whole weight of a body appears to act. An object is stable when its centre of gravity lies above its base, and it topples when the line of action of its weight falls outside the base. A low centre of gravity and a wide base both increase stability, which is why racing cars are built low and wide.
重心是物体全部重力看起来作用的那个点。当重心位于支撑面之上时物体稳定；当重力作用线落在支撑面之外时物体就会翻倒。低重心和宽支撑面都能提高稳定性，所以赛车做得又低又宽。
nbsp; P = W ÷ t efficiency = useful output ÷ total input × 100%
it can be transferred or stored but never created or destroyed. Kinetic energy is the energy of movement, Eₖ = ½ m v², and gravitational potential energy is stored energy due to height, Eₚ = m g h. Power is the rate of doing work, P = W ÷ t, measured in watts (W). Efficiency compares useful output with total input and is always below 100% because energy is dissipated, usually as heat.
当力使物体沿力的方向移动时就说做了功：W = F d，单位是焦耳（J）。能量是做功的本领，且守恒：可以转移或储存，但不会创生或消灭。动能是运动具有的能量，Eₖ = ½ m v²；重力势能是由于高度储存的能量，Eₚ = m g h。功率是做功的快慢，P = W ÷ t，单位是瓦特（W）。效率比较有用输出与总输入，总是低于 100%，因为能量会耗散，通常以热的形式散失。
5. Heat, Temperature and Specific Heat Capacity | 热量、温度与比热容
Heat and temperature are not the same thing. Temperature measures the average kinetic energy of the particles in a substance and is measured with a thermometer in degrees Celsius (°C) or kelvin (K). Heat, or thermal energy, is the total energy transferred from a hotter body to a colder one and is measured in joules. The kinetic particle model explains temperature: the hotter a substance, the faster its particles vibrate or move on average.
热量与温度并不相同。温度衡量物质中粒子的平均动能，用温度计以摄氏度（°C）或开尔文（K）测量。热量（热能）是从较热物体转移到较冷物体的总能量，用焦耳测量。微粒动理论解释了温度：物质越热，其粒子平均振动或运动得越快。
E = m c Δθ absolute temperature: T (K) = θ (°C) + 273
°C). Water has a high specific heat capacity of about 4200 J/(kg °C), which is why it is used in hot-water bottles and car cooling systems. Specific latent heat is the energy needed to change the state of 1 kg of a substance without changing its temperature: E = m L. During melting or boiling, energy goes into breaking bonds rather than raising temperature, so the thermometer reading stays constant.
比热容是使 1 kg 某物质温度升高 1 °C 所需的能量，用 E = m c Δθ 计算，其中 c 的单位是 J/(kg °C)。水的比热容高达约 4200 J/(kg °C)，因此常用作热水袋和汽车冷却系统的介质。比潜热是在温度不变的情况下使 1 kg 物质发生状态变化所需的能量：E = m L。在熔化或沸腾过程中，能量用于破坏粒子间的结合而不是升高温度，所以温度计读数保持不变。
6. Thermal Energy Transfer and Gas Behaviour | 热传递与气体行为
Thermal energy travels by three mechanisms. Conduction happens mainly in solids: particles at the hot end vibrate more, collide with neighbours and pass energy along, and metals conduct well because of their free electrons. Convection happens in fluids: heated fluid expands, becomes less dense and rises, while cooler fluid sinks, forming a convection current. Radiation is the transfer of energy by infrared waves, needs no medium at all, and travels fastest from dull black surfaces; shiny silver surfaces are poor emitters and good reflectors, which is why survival blankets are shiny.
热传递有三种方式。传导主要发生在固体中：热端粒子振动加剧，与邻近粒子碰撞并传递能量；金属因有自由电子而导热良好。对流发生在流体中：受热流体膨胀、密度变小而上升，较冷的流体下沉，形成对流。辐射是通过红外线传递能量，完全不需要介质；表面暗黑粗糙的物体辐射最快，而光亮银白的表面是差发射体、良反射体，所以急救毯做成银色。
The kinetic particle model also explains gas pressure: gas particles move randomly at high speed, collide with the container walls and exert a force over the wall area. Heating a fixed volume of gas increases the average particle speed and the collision rate, raising the pressure. For a fixed mass of gas at constant temperature, pressure and volume are inversely proportional.
微粒动理论也可以解释气体压强：气体粒子高速无规则运动，撞击容器壁并在壁面上产生作用力。对固定体积的气体加热会提高粒子平均速率和碰撞频率，从而增大压强。对固定质量的气体，在温度不变时，压强与体积成反比。
p₁ V₁ = p₂ V₂ (constant temperature, fixed mass of gas)
7. Waves: Properties and Behaviour | 波的性质与行为
avelength λ is the distance between two successive crests, the frequency f is the number of complete waves passing a point each second (in hertz, Hz), and the period T = 1 ÷ f is the time for one complete wave. The wave equation links them all: v = f λ, where v is the wave speed in m/s.
波是传递能量而不传递物质的扰动。振幅是偏离平衡位置的最大距离；波长 λ 是相邻两个波峰之间的距离；频率 f 是每秒通过某点的完整波数（单位赫兹，Hz）；周期 T = 1 ÷ f 是完成一个完整波所需的时间。波速公式把它们联系起来：v = f λ，其中 v 是波速，单位 m/s。
v = f λ T = 1 ÷ f
In transverse waves the particles vibrate at right angles to the direction of energy transfer, as in light and water ripples. In longitudinal waves the particles vibrate along the direction of travel, as in sound, where the pattern of compressions and rarefactions carries the energy. All waves can be reflected, refracted and diffracted, and diffraction is most noticeable when the gap or obstacle is about the same size as the wavelength.
横波中粒子振动方向与能量传播方向垂直，光和水波都是横波。纵波中粒子沿传播方向振动，声波就是纵波，由密部和疏部传递能量。所有波都能发生反射、折射和衍射，当缝宽或障碍物尺寸与波长相近时衍射最明显。
8. Light, Sound and the Electromagnetic Spectrum | 光、声与电磁波谱
Light travels in straight lines and reflects obeying two laws: the angle of incidence equals the angle of reflection, and the incident ray, reflected ray and normal all lie in the same plane. A plane mirror forms a virtual image that is the same size as the object, laterally inverted and as far behind the mirror as the object is in front. Refraction occurs because light changes speed when it crosses a boundary; going from air into glass or water it slows down and bends towards the normal, and it bends away from the normal on leaving a denser medium.
光沿直线传播，反射遵循两条定律：入射角等于反射角，且入射光线、反射光线与法线在同一平面内。平面镜成虚像，像与物等大、左右相反，像到镜面的距离等于物到镜面的距离。折射是由于光穿过界面时速度改变：从空气进入玻璃或水时速度减小、向法线偏折；离开较密介质时则偏离法线。
When light travels from a denser medium to a less dense one, total internal reflection can occur if the angle of incidence exceeds the critical angle. This is the principle behind optical fibres and glass prisms in periscopes. A converging lens brings parallel rays to the principal focus and forms real images used in cameras and the eye; a diverging lens spreads rays and forms a virtual image used to correct short sight.
当光从较密介质射向较疏介质，且入射角大于临界角时，会发生全反射。这是光纤和潜望镜中玻璃棱镜的工作原理。凸透镜把平行光会聚到主焦点，成实像，用于照相机和人眼；凹透镜使光线发散，成虚像，用于矫正近视。
/s in air, faster in liquids and fastest in solids, and echoes are reflected sound used in sonar and ultrasound scanning. The electromagnetic spectrum, from longest to shortest wavelength, runs radio, microwave, infrared, visible light, ultraviolet, X-rays and gamma rays; all travel at 3 × 10⁸ m/s in a vacuum and differ in frequency, wavelength and use.
声是由振动产生的纵波，必须有介质才能传播，因此不能在真空中传播。声在空气中速度约 340 m/s，在液体中更快，在固体中最快；回声是声的反射，用于声呐和超声扫描。电磁波谱按波长从长到短依次为无线电波、微波、红外线、可见光、紫外线、X 射线和 γ 射线；在真空中都以 3 × 10⁸ m/s 传播，区别在于频率、波长和用途。
9. Charge, Current and Circuits | 电荷、电流与电路
(A), Q in coulombs (C) and t in seconds. Charge is carried in metals by free electrons moving from the negative terminal to the positive terminal, while conventional current is drawn from positive to negative. Current is measured with an ammeter connected in series, and potential difference (voltage) is measured with a voltmeter connected in parallel across a component.
电流是电荷的流动速率：I = Q ÷ t，其中 I 的单位是安培（A），Q 的单位是库仑（C），t 的单位是秒。金属中电荷由自由电子从电源负极移向正极来输送，而规定的电流方向是从正极到负极。电流用串联的电流表测量，电压（电势差）用并联在元件两端的电压表测量。
ries: I is the same everywhere parallel: V is the same across each branch
In a series circuit the current is the same at every point and the supply voltage is shared between components; if one lamp fails the whole circuit stops. In a parallel circuit the voltage across each branch is the same and the total current is the sum of the branch currents, so lamps work independently. Electromotive force (e.m.f.) is the energy transferred per unit charge by the source, measured in volts, and energy is transferred when charge flows through a component.
串联电路中各处电流相同，电源电压由各元件分压；若一个灯泡损坏整条电路都会停止工作。并联电路中各支路电压相同，总电流等于各支路电流之和，所以各灯泡可独立工作。电动势（e.m.f.）是电源每单位电荷所转移的能量，单位伏特；电荷通过元件时发生能量转移。
10. Resistance, Electrical Power and Safety | 电阻、电功率与用电安全
R, where R is in ohms (Ω). An ohmic conductor at constant temperature has a current directly proportional to the voltage, giving a straight line graph through the origin. The resistance of a wire increases with length and decreases with greater cross-sectional area; it also depends on the material and, for metals, rises with temperature because lattice ions vibrate more and obstruct the electrons.
电阻衡量电流通过的难易程度，定义为 V = I R，其中 R 的单位是欧姆（Ω）。在温度不变时，欧姆导体的电流与电压成正比，图像是过原点的直线。导线的电阻随长度增大而增大，随横截面积增大而减小；电阻还取决于材料，对金属而言温度升高时电阻增大，因为晶格离子振动加剧，阻碍电子通过。
V = I R P = V I = I² R E = P t
nergy transferred is E = P t in joules, or kilowatt-hours for domestic bills. A thermistor' resistance falls as it gets hotter and is used in thermostats; a light-dependent resistor' ire near 0 V and an earth wire connected to the metal case for safety. Fuses, circuit breakers and double insulation prevent electric shock, and a fuse rating must be just above the normal working current.
电功率是能量转移的速率：P = V I，对电阻也可写成 I² R；转移的能量 E = P t，单位焦耳，家庭电费则常用千瓦时。热敏电阻温度升高时阻值下降，用于恒温器；光敏电阻在光照强时阻值下降，用于自动照明。市电是交流电，火线约 230 V，中性线接近 0 V，地线连接金属外壳以保证安全。熔断器、断路器和双重绝缘都能防止触电，熔丝的额定电流应略高于正常工作电流。
11. Magnetism and Electromagnetism | 磁学与电磁感应
Magnets have north and south poles, and unlike poles attract while like poles repel. A magnetic field is the region around a magnet where a magnetic force is felt, shown by field lines running from north to south outside the magnet, with the strongest field where the lines are closest together. Iron, steel, nickel and cobalt are magnetic materials; soft iron is easily magnetised and demagnetised and is used for electromagnet cores, while steel keeps its magnetism and is used for permanent magnets.
磁铁有 N 极和 S 极，异极相吸、同极相斥。磁场是磁铁周围能感受到磁力的区域，用磁感线表示，在磁铁外部由 N 极指向 S 极；磁感线最密处磁场最强。铁、钢、镍和钴都是磁性材料；软铁容易磁化也容易退磁，用作电磁铁铁芯；钢能保持磁性，用于制造永磁体。
A current-carrying wire produces a magnetic field around it, and winding the wire into a solenoid with an iron core makes an electromagnet whose strength increases with current, number of turns and core material. A current in a magnetic field experiences a force, which is the basis of the electric motor, and the direction is given by the left-hand rule. Electromagnetic induction is the opposite effect: moving a magnet into a coil, or a conductor across a magnetic field, generates an e.m.f. whose size increases with speed, field strength and number of turns, and this is how generators and transformers work.
通电导线周围会产生磁场；把导线绕成螺线管并插入铁芯就构成电磁铁，其磁性强弱随电流、匝数和铁芯材料而增大。磁场中的通电导线会受到力的作用，这是电动机的原理，方向可用左手定则判断。电磁感应是相反的过程：把磁铁插入线圈，或让导体切割磁感线，就会产生电动势，其大小随速度、磁场强度和匝数增加而增大，发电机和变压器正是基于这一原理。
12. Atomic Physics and Radioactivity | 原子物理与放射性
An atom has a small, dense, positively charged
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