📚 Year 11 WJEC Science: Formula & Theorem Quick Reference | Year 11 WJEC 科学：公式定理速查手册
This quick reference handbook brings together the essential formulas and theorems you need to master for Year 11 WJEC Science. Covering Physics, Chemistry and Biology, it provides clear definitions, standard units and step-by-step application of each relationship. Use it to test yourself, complete practice questions and ensure you are fully prepared for your exams.
这本速查手册汇集了 Year 11 WJEC 科学必须掌握的核心公式和定理。涵盖物理、化学和生物，提供清晰的定义、标准单位以及每个关系的分步应用。用它来自测、完成练习题，确保为考试做好充分准备。
1. Speed, Distance and Time | 速度、距离与时间
Speed is the rate at which an object covers distance. The average speed can be found by dividing the total distance travelled by the time taken. The relationship is:
v = s / t
where v is speed (metres per second, m/s), s is distance (metres, m) and t is time (seconds, s). On a distance–time graph, the gradient of the line represents speed. A steeper slope indicates a higher speed.
速度是物体通过距离的快慢程度。平均速度可以通过总距离除以所用时间求得。关系式为：
v = s / t
其中 v 是速度（米/秒，m/s），s 是距离（米，m），t 是时间（秒，s）。在距离–时间图上，直线的斜率代表速度。斜率越陡表示速度越快。
2. Acceleration, Force and Momentum | 加速度、力与动量
Acceleration is the rate of change of velocity. It can be calculated using the change in velocity over time:
a = (v − u) / t
where a is acceleration (m/s²), v is final velocity (m/s), u is initial velocity (m/s) and t is time (s). Newton's second law links resultant force, mass and acceleration:
F = m a
Here F is force (newtons, N), m is mass (kg) and a is acceleration (m/s²). Weight is the force of gravity on a mass:
W = m g
N/kg). In WJEC Higher Tier, you also need momentum p = m v, where p is momentum (kg m/s).
加速度是速度变化的快慢。可以利用速度变化量除以时间计算：
a = (v − u) / t
其中 a 是加速度（米/秒²），v 是末速度（m/s），u 是初速度（m/s），t 是时间（秒）。牛顿第二定律将合力、质量和加速度联系在一起：
F = m a
这里 F 是力（牛，N），m 是质量（kg），a 是加速度（m/s²）。重量是质量所受的重力：
W = m g
其中 g 是重力场强度（N/kg，在地球上约 10 N/kg）。在 WJEC 高阶内容中，还需掌握动量 p = m v，其中 p 是动量（kg m/s）。
3. Work, Energy and Power | 功、能量与功率
Work done is the energy transferred when a force moves an object. It is given by:
W = F d
W is work done (joules, J), F is force (N) and d is distance moved in the direction of the force (m). The kinetic energy of a moving object is:
Eₖ = ½ m v²
Gravitational potential energy gained when lifting an object is:
Eₚ = m g h
where h is the change in height (m). Power is the rate of energy transfer:
P = W / t or P = E / t
Efficiency tells you how much of the input energy is usefully transferred:
Efficiency = (Useful output energy / Total input energy) × 100%
功是力使物体移动时转移的能量。公式为：
W = F d
W 是功（焦，J），F 是力（N），d 是沿力方向移动的距离（m）。运动物体的动能为：
Eₖ = ½ m v²
举起物体时增加的重力势能为：
Eₚ = m g h
其中 h 是高度变化（m）。功率是能量转移的速率：
P = W / t 或 P = E / t
效率表示输入能量有多少被有效转移：
效率 = （有用输出能量 / 总输入能量） × 100%
4. Electrical Circuits | 电路
Ohm's law states that the current through a resistor is directly proportional to the potential difference across it, provided temperature remains constant:
V = I R
V is voltage (volts, V), I is current (amperes, A) and R is resistance (ohms, Ω). Electrical power can be calculated in several ways:
P = I V or P = I² R
Energy transferred by an electrical appliance is:
E = P t or E = I V t
Charge flow relates to current and time:
Q = I t
tance is Rₜ = R₁ + R₂. For parallel resistors, the total is found from 1/Rₜ = 1/R₁ + 1/R₂.
欧姆定律指出，在温度保持不变的条件下，通过电阻器的电流与其两端的电势差成正比：
V = I R
V 是电压（伏特，V），I 是电流（安培，A），R 是电阻（欧姆，Ω）。电功率有多种计算方式：
P = I V 或 P = I² R
用电器转移的能量为：
E = P t 或 E = I V t
电荷量与电流和时间的关系为：
Q = I t
对于串联电阻，总电阻 Rₜ = R₁ + R₂。对于并联电阻，总电阻满足 1/Rₜ = 1/R₁ + 1/R₂。
5. Waves | 波
The wave equation relates wave speed, frequency and wavelength:
v = f λ
where v is wave speed (m/s), f is frequency (hertz, Hz) and λ is wavelength (metres, m). Frequency and period are inverses:
f = 1 / T
Here T is the period (the time for one complete wave to pass, measured in seconds). This applies to all waves, including sound and electromagnetic waves.
波速方程将波速、频率和波长联系起来：
v = f λ
其中 v 是波速（m/s），f 是频率（赫兹，Hz），λ 是波长（米，m）。频率与周期互为倒数：
f = 1 / T
这里 T 是周期（一个完整波通过某点所需的时间，单位为秒）。此关系适用于所有波，包括声波和电磁波。
6. Density, Pressure and Specific Heat Capacity | 密度、压强与比热容
Density measures the mass contained in a unit volume:
ρ = m / V
ρ is density (kg/m³), m is mass (kg) and V is volume (m³). Pressure due to a solid on a surface is force per unit area:
P = F / A
In a liquid, pressure increases with depth:
P = ρ g h
where h is the depth below the surface (m). The energy needed to raise the temperature of a substance is given by the specific heat capacity formula:
ΔE = m c Δθ
ΔE is energy change (J), m is mass (kg), c is specific heat capacity (J/kg °C) and Δθ is temperature change (°C).
密度衡量单位体积
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