📚 Year 11 SQA Physics: Core Knowledge Points Review | Year 11 SQA 物理：核心知识点梳理
This article provides a structured summary of the essential topics in Year 11 SQA Physics, covering kinematics, forces, energy, electricity, waves, radioactivity, gas laws and cosmology. Each section pairs an English explanation with a Chinese translation to help you master the core concepts and prepare effectively for your National 5 assessment.
本文系统梳理了 Year 11 SQA 物理的核心知识点，涵盖运动学、力、能量、电学、波、放射性、气体定律与宇宙学。每个要点均配有英文与中文配对讲解，帮助你牢固掌握关键概念，高效备考 National 5 评估。
1. Scalars and Vectors | 标量与矢量
In physics, quantities are divided into scalars and vectors. A scalar quantity has magnitude (size) only. Examples include speed, distance, mass, time and energy.
在物理中，物理量分为标量和矢量。标量只有大小，例如速率、路程、质量、时间和能量。
A vector quantity has both magnitude and direction. Velocity, displacement, force and acceleration are all vectors. When adding vectors, you must take direction into account.
矢量既有大小又有方向，如速度、位移、力和加速度。矢量相加时必须考虑方向。
Distance is how much ground an object has covered, while displacement is the shortest straight-line distance from start to finish in a specific direction. Similarly, speed is the rate of change of distance, whereas velocity is the rate of change of displacement.
路程是物体经过的路径总长度，位移则是从起点指向终点的有向直线距离。相应地，速率是路程的变化率，速度是位移的变化率。
2. Speed, Velocity and Acceleration | 速率、速度与加速度
The average speed of an object is calculated by dividing the total distance travelled by the time taken: v = d / t. For constant velocity, the same formula applies with displacement.
物体的平均速率等于经过的总路程除以所用时间：v = d / t。匀速直线运动时，速度可用位移除以时间求得。
Acceleration is the change in velocity per unit time. The equation is a = (v – u) / t, where u is initial velocity and v is final velocity. Acceleration can be positive (speeding up) or negative (slowing down, also called deceleration).
加速度是单位时间内速度的变化量，公式为 a = (v – u) / t，其中 u 为初速度，v 为末速度。加速度可为正（加速运动）或负（减速运动）。
Velocity–time graphs provide a lot of information: the gradient gives acceleration, the area under the graph gives displacement, and a horizontal line indicates constant velocity.
速度–时间图像包含丰富信息：斜率表示加速度，图线与时间轴围成的面积表示位移，水平线段表示匀速运动。
3. Forces and Newton’s Laws | 力与牛顿定律
Forces are pushes or pulls that can change the motion or shape of an object. They are measured in newtons (N) and are vectors. Friction opposes motion between two surfaces in contact.
力是能改变物体运动状态或形状的推或拉，单位是牛顿（N），是矢量。摩擦力阻碍接触面之间的相对运动。
Newton’s first law states that an object remains at rest or moves with constant velocity unless acted on by an unbalanced force. Newton’s second law links unbalanced force, mass and acceleration: F = m a.
牛顿第一定律指出，若无净外力作用，物体将保持静止或匀速直线运动状态。牛顿第二定律将净外力、质量与加速度联系起来：F = m a。
Weight is the force of gravity acting on an object. It is calculated using W = m g, where g is the gravitational field strength (10 N/kg on Earth in SQA problems). Mass is a scalar; weight is a vector.
重量是作用在物体上的重力，可由 W = m g 计算，g 为重力场强度（SQA 题目中地球取 10 N/kg）。质量是标量，重量是矢量。
4. Work, Energy and Power | 做功、能量和功率
Work is done when a force moves an object through a distance. The work done is given by W = F d, where F is the force in the direction of motion. Work is measured in joules (J).
力使物体沿力的方向移动一段距离时便做了功。做功的计算式为 W = F d，F 为运动方向上的力，功的单位是焦耳（J）。
Energy is the ability to do work. Gravitational potential energy gained by an object lifted through a height h is Ep = m g h. Kinetic energy of a moving object is Ek = ½ m v².
能量是做功的能力。物体被举高 h 时获得的引力势能为 Eₚ = m g h。运动物体的动能为 Eₖ = ½ m v²。
The principle of conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another. Power is the rate of doing work: P = W / t, measured in watts (W).
能量守恒定律指出，能量既不能创造也不能消灭，只能从一种形式转化为另一种形式。功率是做功的快慢：P = W / t，单位是瓦特（W）。
5. Electric Circuits: Current, Voltage and Resistance | 电路：电流、电压和电阻
Electric current is the flow of charge. Direct current (d.c.) flows in one direction. Current I is measured in amperes (A), and charge Q is measured in coulombs (C). The relationship is Q = I t.
电流是电荷的定向移动。直流电沿一个方向流动。电流 I 的单位是安培（A），电荷量 Q 的单位是库仑（C），关系式为 Q = I t。
Potential difference (voltage) between two points is the energy transferred per coulomb of charge. It is measured in volts (V). Resistance R is the opposition to current, measured in ohms (Ω).
两点间的电势差（电压）是每库仑电荷转移的能量，单位是伏特（V）。电阻 R 是导体对电流的阻碍作用，单位是欧姆（Ω）。
Components in a circuit are often connected in series or parallel. In a series circuit, the current is the same everywhere, while the supply voltage is shared. In a parallel circuit, the voltage across each branch is the same, and the currents add up.
电路元件常以串联或并联方式连接。串联电路中各处电流相等，电源电压被各元件分压；并联电路中各支路两端电压相等，干路电流等于各支路电流之和。
6. Ohm’s Law and Practical Circuit Rules | 欧姆定律与实用电路规则
Ohm’s law states that for a resistor at constant temperature, the current is directly proportional to the potential difference: V = I R. A component that obeys this law gives a straight-line V–I graph through the origin.
欧姆定律指出，在温度不变的条件下，通过电阻的电流与两端电压成正比：V = I R。遵循欧姆定律的元件的 V–I 图像是一条过原点的直线。
For a fixed resistor, resistance stays constant. A filament lamp does not obey Ohm’s law because its resistance increases as temperature rises. A diode only allows current to flow in one direction.
定值电阻的阻值保持不变。白炽灯不遵循欧姆定律，因为其电阻随温度升高而增大。二极管只允许电流单向通过。
When analysing mixed circuits, you can combine resistors in series with Rtotal = R₁ + R₂ + …, and for resistors in parallel, the total resistance is found using 1 / Rtotal = 1 / R₁ + 1 / R₂.
分析混联电路时，串联总电阻为 Rₜ = R₁ + R₂ + …，并联总电阻满足 1 / Rₜ = 1 / R₁ + 1 / R₂。
7. Electrical Power and Energy Transfer | 电功率和能量转移
Electrical power is the rate at which electrical energy is converted into other forms. It can be calculated using P = I V, or with the alternatives P = I² R and P = V² / R when appropriate.
电功率表示电能转化为其他形式能的快慢。可用 P = I V 计算，也可根据情况使用 P = I² R 或 P = V² / R。
The energy transferred in a circuit is given by E = P t or E = I V t. In the home, electrical energy is usually measured in kilowatt-hours (kW h), where 1 kW h equals 3.6 × 10⁶ J.
电路中转移的能量由 E = P t 或 E = I V t 给出。家庭用电通常以千瓦时（kW h）计量，1 kW h 等于 3.6 × 10⁶ J。
Efficiency (η) is the ratio of useful output energy or power to total input energy or power. Because of conservation of energy, efficiency is always ≤ 1 (or ≤ 100%).
效率（η）是指有用输出能量（或功率）与总输入能量（或功率）之比。由于能量守恒，效率总是 ≤ 1（或 ≤ 100%）。
8. Waves: Types and the Wave Equation | 波的类型和波动方程
Waves transfer energy without transferring matter. There are two main types: transverse waves (e.g., light, water ripples) where the vibration is perpendicular to the direction of energy transfer, and longitudinal waves (e.g., sound) where the vibration is parallel.
波传递能量而不传递物质。主要分为两类：横波（如光、水波）振动方向与能量传播方向垂直；纵波（如声波）振动方向与能量传播方向平行。
Key wave quantities include wavelength (λ), frequency (f), period (T) and amplitude. The relationship between wave speed, frequency and wavelength is the wave equation: v = f λ.
波的特征量包括波长（λ）、频率（f）、周期（T）和振幅。波速、频率和波长之间的关系由波动方程给出：v = f λ。
Diffraction occurs when waves spread out after passing through a gap or around an obstacle. The effect is most noticeable when the gap width is similar to the wavelength.
衍射是波通过狭缝或绕过障碍物后向四周扩展的现象。当狭缝宽度与波长相近时，衍射现象最明显。
9. Electromagnetic Spectrum | 电磁波谱
The electromagnetic spectrum is a family of transverse waves that all travel at the speed of light (3.0 × 10⁸ m/s) in a vacuum. In order of increasing frequency (and decreasing wavelength), the groups are: radio, microwave, infrared, visible light, ultraviolet, X-rays and gamma rays.
电磁波谱是一组在真空中均以光速（3.0 × 10⁸ m/s）传播的横波。按频率递增（波长递减）的顺序排列为：无线电波、微波、红外线、可见光、紫外线、X 射线和伽马射线。
Different EM waves carry different amounts of energy and have different uses and dangers. Radio waves are used in communication, microwaves in cooking and radar, infrared in thermal imaging, visible light for sight, ultraviolet in fluorescent lamps and sterilisation, X-rays for medical imaging, and gamma rays for cancer treatment.
不同电磁波携带的能量不同，用途和危害各异。无线电波用于通信，微波用于烹饪和雷达，红外线用于热成像，可见光用于视觉，紫外线用于荧光灯和消毒，X 射线用于医学成像，伽马射线用于癌症治疗。
Higher-frequency EM waves (UV, X-rays, gamma rays) have enough energy to ionise atoms and can damage living tissue. Gamma rays are the most penetrating and ionising, but also the most hazardous.
高频电磁波（紫外线、X 射线、伽马射线）具有足够的能量使原子电离，可损伤活体组织。伽马射线穿透力和电离能力最强，也是最危险的辐射。
10. Radioactivity and Nuclear Radiation | 放射性与核辐射
Radioactivity is the spontaneous emission of radiation from an unstable nucleus. The three main types are alpha (α), beta (β) and gamma (γ). Alpha particles are helium nuclei (⁴₂He), beta particles are fast electrons (⁰₋₁e), and gamma rays are electromagnetic waves.
放射性是不稳定原子核自发发射辐射的现象。主要有三种类型：α 粒子（氦核 ⁴₂He）、β 粒子（高速电子 ⁰₋₁e）和 γ 射线（电磁波）。
Alpha radiation is highly ionising but poorly penetrating, stopped by paper or a few centimetres of air. Beta radiation is moderately ionising and penetrating, stopped by a few millimetres of aluminium. Gamma radiation is weakly ionising but very penetrating, requiring thick lead or concrete to reduce its intensity significantly.
α 辐射电离能力强，穿透力弱，纸张或几厘米空气即可阻挡。β 辐射电离能力和穿透力均适中，几毫米铝板可阻挡。γ 辐射电离能力弱但穿透力很强，需要厚铅板或混凝土才能显著减弱其强度。
The activity of a radioactive source is the number of decays per second, measured in becquerels (Bq). The half-life is the time taken for the activity (or the number of radioactive nuclei) to drop to half its original value.
放射源的活度是每秒衰变次数，单位为贝克勒尔（Bq）。半衰期是活度（或放射性核的数目）减少到初始值一半所需的时间。
Nuclear equations balance the total atomic number and mass number. For example, alpha decay of uranium-238: ²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂He. Background radiation comes from natural sources such as rocks, cosmic rays and radon gas.
核反应方程要求总原子序数和总质量数守恒。例如铀-238的α衰变：²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂He。背景辐射来源于岩石、宇宙射线和氡气等天然源。
11. Gas Laws and the Kinetic Model | 气体定律与分子动理论
The pressure of a fixed mass of gas at constant temperature is inversely proportional to its volume (Boyle’s law): p₁ V₁ = p₂ V₂. At constant volume, pressure is directly proportional to the kelvin temperature: p₁ / T₁ = p₂ / T₂.
一定质量的气体在温度不变时，压强与体积成反比（玻意耳定律）：p₁ V₁ = p₂ V₂。体积不变时，压强与开尔文温度成正比：p₁ / T₁ = p₂ / T₂。
The volume of a fixed mass of gas at constant pressure is directly proportional to its kelvin temperature (Charles’ law): V₁ / T₁ = V₂ / T₂. When using these laws, temperature must always be in kelvin (K).
一定质量的气体在压强不变时，体积与开尔文温度成正比（查理定律）：V₁ / T₁ = V₂ / T₂。使用气体定律时，温度必须使用开尔文（K）。
The kinetic model explains these laws by considering gas molecules in constant random motion. Raising the temperature increases the average kinetic energy of the molecules, so they hit the container walls harder and more often, increasing pressure.
分子动理论通过气体分子的无规则运动来解释这些定律。温度升高使分子平均动能增大，导致分子撞击器壁更猛烈、更频繁，从而增大压强。
12. Cosmology and the Expanding Universe | 宇宙学与膨胀宇宙
Most galaxies show a redshift in their light, meaning the observed wavelengths are longer than those emitted. This indicates that galaxies are moving away from us, supporting the idea that the Universe is expanding.
大多数星系的光谱显示红移，即观测到的波长比发射波长要长。这表明星系正在远离我们，支持宇宙正在膨胀的观点。
The greater the redshift of a galaxy, the faster it is receding. This relationship, known as Hubble’s law, suggests that all distant galaxies are moving apart, with the most distant moving the fastest.
星系红移越大，其退行速度越快。这一关系（哈勃定律）表明所有遥远星系都在相互远离，且越远的星系退行越快。
The Big Bang theory proposes that the Universe began from an extremely hot, dense point and has been expanding ever since. Cosmic microwave background radiation (CMBR) is considered leftover heat from the Big Bang and provides strong evidence for this theory.
大爆炸理论认为宇宙起源于一个极高温、致密的点，并自此不断膨胀。宇宙微波背景辐射（CMBR）被认为是大爆炸的余热，为该理论提供了有力证据。
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