KS3 OCR Physics: Formula and Theorem Quick Reference Handbook | KS3 OCR 物理：公式定理速查手册

📚 KS3 OCR Physics: Formula and Theorem Quick Reference Handbook | KS3 OCR 物理：公式定理速查手册

Welcome to the KS3 OCR Physics quick reference handbook. This guide contains the essential formulas and theorems you need to know for the Key Stage 3 curriculum. Each formula is presented clearly with its variables and units, helping you to solve problems and understand physical relationships. Use this handbook for rapid revision before tests and to build a strong foundation for GCSE Physics.

欢迎使用 KS3 OCR 物理快速参考手册。本手册汇集了关键阶段 3 课程必须掌握的核心公式和定理。每个公式都清晰呈现，配有变量和单位说明，帮助你解题并理解物理关系。可用于考前快速复习，为 GCSE 物理打下坚实基础。

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1. Speed | 速度

Average speed tells you how fast an object is moving over a certain distance. It is calculated by dividing the total distance travelled by the total time taken. Speed is a scalar quantity and can be measured in metres per second (m/s), kilometres per hour (km/h) or miles per hour (mph).

v = s / t

平均速度表示物体在一段距离上运动的快慢。它等于总路程除以总时间。速度是标量，通常用米每秒（m/s）、千米每小时（km/h）或英里每小时（mph）作为单位。在公式中，v 代表速度，s 代表路程，t 代表时间。注意区分平均速度和瞬时速度——本公式给出的是平均速度。

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2. Acceleration | 加速度

Acceleration is the rate of change of velocity. If an object speeds up, it has positive acceleration; if it slows down, the acceleration is negative (often called deceleration). Acceleration is a vector quantity and its SI unit is metres per second squared (m/s²).

a = (v − u) / t

加速度是速度变化的快慢。物体加速时加速度为正，减速时加速度为负（常称为减速度）。加速度是矢量，国际单位是米每二次方秒（m/s²）。公式中，a 表示加速度，v 表示末速度，u 表示初速度，t 表示速度变化所用的时间。计算时务必注意初末速度的方向。

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3. Force and Motion | 力与运动

Newton’s Second Law states that the resultant force acting on an object is equal to its mass multiplied by its acceleration. Force is measured in newtons (N), mass in kilograms (kg) and acceleration in m/s². This law explains why a larger force produces a greater acceleration, and why heavier objects accelerate more slowly for the same push.

F = m a

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它的加速度。力的单位是牛顿（N），质量的单位是千克（kg），加速度的单位是 m/s²。这个定律解释了为什么力越大加速度越大，以及为什么相同的推力下质量越大的物体加速越慢。

Weight is the gravitational force acting on an object. Near the Earth’s surface, the weight can be found by multiplying the mass by the gravitational field strength (g). On Earth, g is approximately 10 N/kg (or more precisely 9.8 N/kg). Weight is a force and should not be confused with mass.

W = m g

重量是地球对物体的引力。在地球表面附近，重量等于质量乘以引力场强度 g。地球上 g 大约为 10 N/kg（更精确为 9.8 N/kg）。重量是力，不要和质量混淆。式中 W 表示重量（单位 N），m 表示质量（kg），g 表示引力场强度（N/kg）。

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4. Pressure | 压强

Pressure is a measure of how concentrated a force is. It is defined as the force acting perpendicularly on a surface divided by the area over which the force is spread. The SI unit of pressure is the pascal (Pa), where 1 Pa = 1 N/m². A sharp knife has a high pressure because the force is concentrated on a small area.

p = F / A

压强表示力的集中程度，等于垂直作用在表面上的力除以受力面积。压强的国际单位是帕斯卡（Pa），1 Pa = 1 N/m²。刀刃锋利是因为力集中在很小的面积上，从而产生较大的压强。公式中 p 代表压强（Pa），F 代表作用力（N），A 代表面积（m²）。计算时需要注意力的方向必须垂直于表面。

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5. Density | 密度

Density describes how much mass is packed into a given volume. It is a material property and can be used to identify substances. The formula relates mass and volume; the SI unit is kilograms per cubic metre (kg/m³), though grams per cubic centimetre (g/cm³) is also common for solids and liquids.

ρ = m / V

密度表示单位体积内所含物质的质量。每种物质都有其特定的密度，可以用于鉴别物质。公式中 ρ（读作 ‘rho’）表示密度，m 表示质量，V 表示体积。国际单位是 kg/m³，常用单位还有 g/cm³。1 g/cm³ = 1000 kg/m³。记住密度是质量与体积的比值，不是重量。

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6. Work, Energy and Power | 功、能与功率

Work is done when a force moves an object in the direction of the force. Work and energy are both measured in joules (J). One joule is the work done when a force of 1 newton moves a distance of 1 metre in the direction of the force.

W = F d

当力使物体沿力的方向移动时，就对物体做了功。功和能量的单位都是焦耳（J）。1 焦耳表示 1 牛顿的力使物体沿力方向移动 1 米所做的功。式中 W 代表功（J），F 代表力（N），d 代表沿力方向移动的距离（m）。

Gravitational potential energy (Ep) is the energy stored in an object because of its height above the ground. The higher the object, the greater its Ep. It depends on mass, gravitational field strength and height.

Ep = m g h

重力势能（Ep）是由于物体被举高而储存的能量。高度越高，重力势能越大。它取决于物体的质量、引力场强度和高度。公式中 m 为质量（kg），g 为引力场强度（N/kg），h 为高度（m）。计算时通常以地面或某个参考面为零势能面。

Kinetic energy (Ek) is the energy an object possesses due to its motion. A faster or heavier object has more kinetic energy. The formula shows that kinetic energy increases with the square of speed, so doubling speed quadruples Ek.

Ek = ½ m v²

动能（Ek）是物体由于运动而具有的能量。速度越快、质量越大，动能越大。公式中 m 是质量（kg），v 是速度（m/s）。注意动能与速度的平方成正比——如果速度变为原来的 2 倍，动能就会变为原来的 4 倍。

Power is the rate at which work is done or energy is transferred. A powerful appliance transfers a lot of energy in a short time. The SI unit of power is the watt (W), where 1 W = 1 J/s.

P = W / t or P = E / t

功率是做功或能量转移的快慢。功率大的设备能够在短时间内转移大量能量。功率的国际单位是瓦特（W），1 W = 1 J/s。公式中 P 代表功率（W），W 代表功（J），E 代表转移的能量（J），t 代表时间（s）。两种形式等价，选择哪一个取决于题目给出的数据。

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7. Electricity – Ohm’s Law and Resistance | 电学 – 欧姆定律与电阻

Ohm’s Law connects potential difference (voltage), current and resistance in a circuit. For a given resistor at constant temperature, the current flowing through it is directly proportional to the potential difference across it. Resistance measures how difficult it is for current to flow and is measured in ohms (Ω).

V = I R

欧姆定律描述了电路中电压、电流和电阻之间的关系。对于温度不变的电阻器，通过它的电流与它两端的电压成正比。电阻表示电流通过的难易程度，单位是欧姆（Ω）。公式中 V 代表电压（V），I 代表电流（A），R 代表电阻（Ω）。由此可以推导出电阻公式 R = V / I。

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8. Wave Properties | 波的性质

Waves transfer energy from one place to another without transferring matter. The speed of a wave is the product of its frequency and wavelength. Frequency is measured in hertz (Hz), wavelength in metres (m), and wave speed in metres per second (m/s).

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