📚 Year 10 WJEC Physics: Formula & Theorem Quick Reference Guide | Year 10 WJEC 物理：公式定理速查手册
This quick reference guide brings together the essential formulas and theorems you will meet in Year 10 WJEC Physics. Understanding how to apply each equation is just as important as memorising it. Use this handbook for revision, homework and exam preparation.
这份速查手册汇总了你在 Year 10 WJEC 物理课程中会遇到的核心公式与定理。记住公式很重要，但更关键的是理解如何应用它们。你可以用它来复习、完成作业和准备考试。
1. Motion and Forces | 运动与力
Average speed is defined as the total distance travelled divided by the time taken: v = s / t, where v is speed (m/s), s is distance (m) and t is time (s).
平均速度定义为走过的总距离除以所用时间：v = s / t，其中 v 是速度（m/s），s 是距离（m），t 是时间（s）。
Acceleration is the rate of change of velocity: a = (v – u) / t, where a is acceleration (m/s²), v is final velocity (m/s), u is initial velocity (m/s).
加速度是速度的变化率：a = (v – u) / t，其中 a 是加速度（m/s²），v 是末速度（m/s），u 是初速度（m/s）。
For constant acceleration, you may also be asked to use v = u + a t and s = u t + ½ a t². The unit of acceleration shows how many m/s are gained or lost every second.
在匀加速运动中，你还可能需要使用 v = u + a t 和 s = u t + ½ a t²。加速度的单位表示每秒钟速度增加或减少了多少 m/s。
Newton’s second law states that the resultant force on an object equals its mass multiplied by its acceleration: F = m a, where F is force (N), m is mass (kg).
牛顿第二定律指出，作用在物体上的合力等于物体的质量乘以加速度：F = m a，其中 F 是力（N），m 是质量（kg）。
Weight is the force of gravity on an object: W = m g, where g is gravitational field strength (on Earth ~9.8 N/kg or often 10 N/kg in WJEC exams).
重量是作用在物体上的重力：W = m g，其中 g 是引力场强度（地球上约为 9.8 N/kg，WJEC 考试中常取 10 N/kg）。
2. Suvat Relations and Graphs | 匀加速运动公式与图像
For an object moving with uniform acceleration, the useful suvat equations are: v = u + a t, v² = u² + 2 a s, and s = u t + ½ a t².
对于匀加速运动的物体，常用的 suvat 方程有：v = u + a t，v² = u² + 2 a s 以及 s = u t + ½ a t²。
A velocity–time graph provides: the gradient gives acceleration, the area under the graph gives displacement, and a horizontal line indicates constant velocity.
速度–时间图像中：斜率给出加速度，图像下的面积给出位移，而水平线表示匀速运动。
On a distance–time graph, the gradient represents speed. A steeper gradient means a higher speed; a flat section means the object is stationary.
在距离–时间图像中，斜率代表速度。斜率越陡，速度越大；水平段表示物体静止。
3. Energy and Work | 能量与功
Work done is energy transferred when a force moves an object: W = F d, where W is work done (J), F is force (N) and d is distance moved in the direction of the force (m).
功是力使物体移动时传递的能量：W = F d，其中 W 是功（J），F 是力（N），d 是物体在力的方向上移动的距离（m）。
Gravitational potential energy: Eₚ = m g h, where h is change in height (m). This is the energy stored due to an object’s position in a gravitational field.
重力势能：Eₚ = m g h，其中 h 是高度变化（m）。它是物体因在引力场中的位置而储存的能量。
Kinetic energy: Eₖ = ½ m v², where v is speed (m/s). Any moving object possesses kinetic energy.
动能：Eₖ = ½ m v²，其中 v 是速度（m/s）。任何运动的物体都具有动能。
Energy is always conserved. It can be transferred from one store to another, but the total energy of a closed system remains constant.
能量总是守恒的。它可以从一个能量储存转移到另一个，但封闭系统的总能量保持不变。
4. Power and Efficiency | 功率与效率
Power is the rate of doing work or transferring energy: P = W / t or P = E / t, where P is power (W), W or E is energy transferred (J) and t is time (s).
功率是做功或传递能量的速率：P = W / t 或 P = E / t，其中 P 是功率（W），W 或 E 是传递的能量（J），t 是时间（s）。
Efficiency measures how much of the input energy is converted into useful output: Efficiency = (useful energy output / total energy input) × 100%. It can also be expressed in terms of power: Efficiency = (useful power output / total power input) × 100%.
效率衡量输入能量中有多少转化为有用的输出：效率 = (有用的能量输出 / 总能量输入) × 100%。也可以用功率表示：效率 = (有用的输出功率 / 总输入功率) × 100%。
No device is 100% efficient; some energy is always transferred to thermal stores of the surroundings, which is wasted energy.
没有任何设备能达到 100% 的效率；总有一部分能量会传递到周围的热能储存中，这就是浪费的能量。
5. Density and Pressure | 密度与压强
Density is mass per unit volume: ρ = m / V, where ρ is density (kg/m³), m is mass (kg) and V is volume (m³).
密度是单位体积的质量：ρ = m / V，其中 ρ 是密度（kg/m³），m 是质量（kg），V 是体积（m³）。
Pressure is the force acting per unit area: P = F / A, where P is pressure (Pa or N/m²), F is force (N) and A is the area (m²) over which the force is applied.
压强是作用在单位面积上的力：P = F / A，其中 P 是压强（Pa 或 N/m²），F 是力（N），A 是力作用的面积（m²）。
Pressure in liquids increases with depth and density: P = h ρ g, where h is the depth (m) of liquid, ρ is density of the liquid (kg/m³) and g is gravitational field strength.
液体内部的压强随深度和密度的增加而增大：P = h ρ g，其中 h 是液体深度（m），ρ 是液体密度（kg/m³），g 是引力场强度。
6. Electricity: Ohm’s Law and Circuits | 电学：欧姆定律与电路
Ohm’s law states that the current through a resistor at constant temperature is directly proportional to the potential difference across it: V = I R, where V is voltage (V), I is current (A) and R is resistance (Ω).
欧姆定律指出，在温度不变时，通过电阻器的电流与其两端的电势差成正比：V = I R，其中 V 是电压（V），I 是电流（A），R 是电阻（Ω）。
Resistance can be found from the gradient of a voltage–current graph. For a fixed resistor, the graph is a straight line through the origin; for a filament lamp, the line curves as temperature increases.
电阻可以从电压–电流图像的斜率求得。对定值电阻，图像是过原点的直线；对灯丝灯泡，由于温度升高，曲线会弯曲。
For resistors in series, the total resistance is the sum of individual resistances: Rₜₒₜₐₗ = R₁ + R₂ + …. For resistors in parallel, the total resistance is found from 1/Rₜₒₜₐₗ = 1/R₁ + 1/R₂ + ….
电阻串联时，总电阻等于各电阻之和：Rₜₒₜₐₗ = R₁ + R₂ + …。电阻并联时，总电阻由 1/Rₜₒₜₐₗ = 1/R₁ + 1/R₂ + … 计算。
In a series circuit, current is the same everywhere; the supply voltage is shared across components. In a parallel circuit, the voltage across each branch is the same; total current equals the sum of branch currents.
在串联电路中，各处的电流相等；电源电压由各元件分担。在并联电路中，各支路两端电压相等；总电流等于各支路电流之和。
7. Electrical Power and Energy Transfer | 电功率与能量转移
Electrical power can be calculated using: P = I V and P = I² R. In WJEC papers, you’ll most often use P = I V to find the power of an appliance.
电功率可以用 P = I V 和 P = I² R 计算。在 WJEC 考试中，最常使用 P = I V 来求电器的功率。
The energy transferred by an electrical device is: E = I V t or E = P t, where t is time in seconds, giving energy in joules. In domestic electricity, energy is often measured in kilowatt-hours (kWh).
用电器转移的能量为：E = I V t 或 E = P t，其中 t 以秒为单位，能量单位为焦耳。在家庭用电中，能量常用千瓦时（kWh）计量。
Kilowatt-hours are calculated by multiplying power in kilowatts by time in hours: energy (kWh) = power (kW) × time (h). This is the unit used on electricity bills.
千瓦时等于以千瓦为单位的功率乘以以小时为单位的时间：能量 (kWh) = 功率 (kW) × 时间 (h)。这是电费账单上使用的单位。
8. Waves: Speed, Frequency and Wavelength | 波：速度、频率与波长
The wave equation links speed, frequency and wavelength: v = f λ, where v is wave speed (m/s), f is frequency (Hz) and λ is wavelength (m).
波速公式将速度、频率和波长联系起来：v = f λ，其中 v 是波速（m/s），f 是频率（Hz），λ 是波长（m）。
Frequency is the number of complete waves passing a point per second; it is the inverse of the period T: f = 1 / T. Period is measured in seconds.
频率是每秒通过某点的完整波的个数；它是周期 T 的倒数：f = 1 / T。周期的单位是秒。
For transverse waves, the oscillations are perpendicular to the direction of energy transfer (e.g. water waves, electromagnetic waves). For longitudinal waves, oscillations are parallel to the direction of energy transfer (e.g. sound waves).
横波的振动方向与能量传递方向垂直（如水波、电磁波）；纵波的振动方向与能量传递方向平行（如声波）。
9. Specific Heat Capacity and Thermal Physics | 比热容与热物理
The energy required to raise the temperature of a substance is given by: Q = m c Δθ, where Q is thermal energy (J), m is mass (kg), c is specific heat capacity (J/(kg°C)) and Δθ is temperature change (°C).
提高物体温度所需的能量公式为：Q = m c Δθ，其中 Q 是热能（J），m 是质量（kg），c 是比热容（J/(kg°C)），Δθ 是温度变化（°C）。
When a substance changes state, its temperature remains constant. The energy supplied breaks or forms molecular bonds rather than increasing kinetic energy. This is explained by the kinetic particle model.
物质发生状态变化时，温度保持不变。所供给的能量用于打破或形成分子间的键，而不是增加动能。这可以用分子运动模型来解释。
In a closed system, heat transfers from hotter regions to cooler regions until thermal equilibrium is reached. Conduction, convection and radiation are the three methods of thermal energy transfer.
在封闭系统中，热量从较热的区域传递到较冷的区域，直到达到热平衡。传导、对流和辐射是热能传递的三种方式。
10. Moments, Levers and Springs | 力矩、杠杆与弹簧
The moment of a force is its turning effect: M = F d, where M is moment (Nm), F is force (N) and d is the perpendicular distance from the pivot to the line of action of the force (m).
力矩是力的转动效果：M = F d，其中 M 是力矩（Nm），F 是力（N），d 是从支点到力作用线的垂直距离（m）。
For a system in equilibrium, the sum of clockwise moments about any pivot equals the sum of anticlockwise moments. This is the principle of moments.
对于处于平衡状态的系统，绕任何支点的顺时针力矩之和等于逆时针力矩之和。这就是力矩平衡原理。
When a spring obeys Hooke’s law, the extension is directly proportional to the applied force, up to its limit of proportionality: F = k x, where k is the spring constant (N/m) and x is extension (m).
当弹簧遵守胡克定律时，在比例极限内，伸长量与所施加的力成正比：F = k x，其中 k 是弹簧常数（N/m），x 是伸长量（m）。
Levers and gears are force multipliers: a small effort can move a larger load if the effort acts further from the pivot than the load does.
杠杆和齿轮是力的倍增器：如果施力点比负载离支点更远，较小的力就可以移动较大的负载。
11. Key Units and Conversions | 关键单位与换算
| Quantity | Symbol | Unit | Abbreviation |
|---|---|---|---|
| distance, displacement | s | metre | m |
| mass | m | kilogram | kg |
| time | t | second | s |
| speed | v | metre per second | m/s |
| acceleration | a | metre per second squared | m/s² |
| force | F | newton | N |
| energy, work | E, W | joule | J |
| power | P | watt | W |
| voltage | V | volt | V |
| current | I | ampere | A |
| resistance | R | ohm | Ω |
Memorising the correct unit for each quantity is essential for substituting correctly into formulas and interpreting the results.
熟记每个物理量的正确单位，对于正确代入公式和解读结果是必不可少的。
12. Using the Formula Sheet Effectively | 高效使用公式表
WJEC provides a formula sheet in the exam, but you still need to know which equation to select and how to rearrange it. Practise converting statements into variables and then matching the correct formula.
WJEC 考试中会提供公式表，但你仍需知道该选哪个方程以及如何变换它。多练习把文字描述转换成变量，然后匹配正确的公式。
Always show your working: write down the formula, substitute the numbers with units, then give the final answer to an appropriate number of significant figures and include the unit.
一定要写出解题步骤：写出公式，代入数值并带上单位，然后给出合理有效数字的最终答案，并附上单位。
If the question asks for an explanation, link the formula to the physical situation. For example, explaining why pressure increases with depth can be done by referring to P = h ρ g.
如果题目要求解释，请将公式与物理情景联系起来。例如，解释压强随深度增加时，可以引用 P = h ρ g。
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