📚 Year 7 Cambridge Physics: Formula & Theorem Quick Reference Handbook | 剑桥7年级物理：公式定理速查手册
This quick reference handbook summarises the essential formulas and theorems covered in the Year 7 Cambridge physics syllabus. Use it as a handy revision tool to check your understanding of key relationships and principles. Each section is paired in English and Chinese so you can master the content and the language with confidence.
这本速查手册汇总了剑桥7年级物理课程中的核心公式与定理。它可以作为你复习时快速查阅关键关系和原理的便携工具。每个部分都配有中英双语对照，帮助你同时掌握学科内容和学术用语。
1. Speed and Motion | 速度与运动
Speed tells us how fast an object moves. The average speed of an object is the total distance travelled divided by the total time taken.
速度表示物体运动的快慢。物体的平均速度等于通过的总路程除以所用的总时间。
speed = distance ÷ time
In symbols: v = d / t, where v represents speed, d represents distance and t represents time. The SI unit of speed is metres per second (m/s).
用符号表示：v = d / t，其中 v 代表速率，d 代表路程，t 代表时间。速度的国际单位是米每秒（m/s）。
When you see a speed in kilometres per hour (km/h), you can convert it to m/s by multiplying by 1000/3600, which simplifies to dividing by 3.6.
如果你看到的速度单位是千米每小时（km/h），可以乘以 1000/3600 换算为 m/s，也就是除以 3.6。
2. Acceleration | 加速度
Acceleration describes how quickly the velocity of an object changes. It can be speeding up, slowing down or changing direction.
加速度描述物体速度变化的快慢。它可以是加速、减速或改变运动方向。
acceleration = change in velocity ÷ time taken
In symbols: a = (v – u) / t, where a is acceleration, v is final velocity, u is initial velocity and t is the time for the change. The unit is metres per second squared (m/s²).
用符号表示：a = (v – u) / t，其中 a 为加速度，v 为末速度，u 为初速度，t 为发生这一变化所用的时间。单位是米每二次方秒（m/s²）。
A negative acceleration means the object is decelerating – its speed is decreasing in the positive direction.
负的加速度意味着物体正在减速——它在正方向上的速率在减小。
3. Mass, Weight and Gravity | 质量、重量与重力
Mass is the amount of matter in an object and is measured in kilograms (kg). Weight is the force of gravity acting on that mass.
质量是物体所含物质的多少，单位是千克（kg）。重量是作用在该质量上的重力大小。
weight = mass × gravitational field strength
In symbols: W = m × g. On Earth, the gravitational field strength g is approximately 10 N/kg (often taken as 9.8 N/kg for more precise work). Weight is measured in newtons (N).
用符号表示：W = m × g。在地球表面，重力场强度 g 约为 10 N/kg（更精确的计算常取 9.8 N/kg）。重量的单位是牛顿（N）。
Your mass stays the same wherever you go, but your weight changes on different planets because g changes.
无论你去哪里，你的质量保持不变，但在不同的行星上你的重量会改变，因为 g 的数值不同。
4. Density | 密度
Density tells us how much mass is packed into a certain volume. It helps explain why some objects float and others sink.
密度表示单位体积内所含质量的多少。它可以解释为什么有些物体会浮起而有些会下沉。
density = mass ÷ volume
In symbols: ρ = m / V, where the Greek letter ρ (rho) stands for density, m for mass and V for volume. The SI unit is kilograms per cubic metre (kg/m³), but grams per cubic centimetre (g/cm³) is also widely used.
用符号表示：ρ = m / V，其中希腊字母 ρ（rho）代表密度，m 为质量，V 为体积。国际单位是千克每立方米（kg/m³），但也常用克每立方厘米（g/cm³）。
To find the density of an irregular solid, you can measure its mass with a balance and its volume by displacement of water in a measuring cylinder.
要测量不规则固体的密度，你可以用天平测出其质量，再用量筒通过排水法测出体积。
5. Forces and Newton’s Laws | 力与牛顿定律
A force is a push or a pull that can change an object’s speed, direction or shape. Newton summarised the behaviour of forces in three laws of motion.
力是推或拉的作用，能够改变物体的速度、方向或形状。牛顿用三条运动定律总结了力的行为。
Newton’s First Law: An object stays at rest or moves with constant velocity unless a resultant force acts on it.
牛顿第一定律： 任何物体都要保持静止或匀速直线运动状态，直到有合力迫使它改变这种状态为止。
Newton’s Second Law: The acceleration of an object is directly proportional to the resultant force and inversely proportional to its mass.
牛顿第二定律： 物体的加速度与所受合力成正比，与物体的质量成反比。
force = mass × acceleration
In symbols: F = m × a. Force is measured in newtons (N), mass in kg and acceleration in m/s². 1 N is the force needed to give a 1 kg mass an acceleration of 1 m/s².
用符号表示：F = m × a。力的单位是牛顿（N），质量单位是 kg，加速度单位是 m/s²。1 N 是使 1 kg 的物体获得 1 m/s² 加速度所需的力。
Newton’s Third Law: Whenever two objects interact, they exert equal and opposite forces on each other.
牛顿第三定律： 当两个物体相互作用时，它们彼此施加的力大小相等、方向相反。
6. Pressure | 压强
Pressure measures how concentrated a force is over an area. A sharp knife cuts easily because it concentrates force onto a very small area, creating high pressure.
压强表示力在面积上的集中程度。锋利的刀容易切割，是因为它将力集中在很小的面积上，产生了较大的压强。
pressure = force ÷ area
In symbols: P = F / A. Pressure is measured in pascals (Pa), where 1 Pa = 1 N/m². Force is in newtons (N) and area in square metres (m²).
用符号表示：P = F / A。压强的单位是帕斯卡（Pa），1 Pa = 1 N/m²。力的单位是牛顿（N），面积的单位是平方米（m²）。
To reduce pressure, you can increase the area over which a force acts – that’s why camels have wide feet for walking on sand.
要减小压强，可以增大受力面积——这就是为什么骆驼有宽大的脚掌，方便在沙地上行走。
7. Moments and Levers | 力矩与杠杆
A moment is the turning effect of a force about a pivot. It depends on the size of the force and its distance from the pivot.
力矩是力对支点产生的转动效应。它取决于力的大小以及力到支点的距离。
moment = force × perpendicular distance from pivot
In symbols: M = F × d, where d is the perpendicular distance from the line of action of the force to the pivot. The unit is newton metre (N m).
用符号表示：M = F × d，其中 d 是力的作用线到支点的垂直距离。力矩的单位是牛·米（N m）。
When an object is balanced, the total clockwise moment equals the total anticlockwise moment. This is the principle of moments.
当一个物体平衡时，顺时针方向的总力矩等于逆时针方向的总力矩。这就是力矩原理。
8. Energy, Work and Power | 能量、功与功率
Energy is the ability to do work. Work is done when a force moves an object in the direction of the force.
能量是做功的能力。当一个力使物体沿力的方向移动时，我们就说力做了功。
work done = force × distance moved in the direction of the force
In symbols: W = F × d. Work and energy are both measured in joules (J). 1 J is the work done when a force of 1 N moves an object 1 m.
用符号表示：W = F × d。功和能量都以焦耳（J）为单位。1 J 就是 1 N 的力使物体沿力的方向移动 1 m 所做的功。
Power is the rate at which work is done or energy is transferred.
功率是做功或能量转化的快慢。
power = work done ÷ time
In symbols: P = W / t. The unit of power is the watt (W), where 1 W = 1 J/s.
用符号表示：P = W / t。功率的单位是瓦特（W），1 W = 1 J/s。
Two common forms of mechanical energy are kinetic energy (KE) and gravitational potential energy (GPE).
两种常见的机械能形式是动能（KE）和重力势能（GPE）。
KE = ½ × mass × speed²
KE = ½ × m × v². Doubling the speed quadruples the kinetic energy.
KE = ½ × m × v²。速度加倍，动能就变为原来的四倍。
GPE = mass × gravitational field strength × height
GPE = m × g × h. Height is measured from a chosen reference level.
GPE = m × g × h。高度是从选定的参考水平面开始测量的。
9. Electric Circuits | 电路
Ohm’s law links voltage, current and resistance in a conductor at constant temperature.
欧姆定律描述了在温度不变的导体中，电压、电流和电阻之间的关系。
voltage = current × resistance
In symbols: V = I × R. Voltage (V) is measured in volts (V), current (I) in amperes (A) and resistance (R) in ohms (Ω).
用符号表示：V = I × R。电压 V 的单位是伏特（V），电流 I 的单位是安培（A），电阻 R 的单位是欧姆（Ω）。
In a series circuit, the current is the same everywhere. The total resistance is the sum of individual resistances, and the sum of the voltages across each component equals the supply voltage.
在串联电路中，各处电流相等。总电阻等于各电阻之和，各元件两端的电压之和等于电源电压。
In a parallel circuit, the voltage across each branch is the same. The total current is the sum of the currents in each branch.
在并联电路中，各支路两端的电压相等。总电流等于各支路电流之和。
10. Wave Properties | 波的特性
Waves transfer energy from one place to another without transferring matter. The speed of a wave depends on its frequency and wavelength.
波能把能量从一处传到另一处，但不传递物质。波的传播速度取决于它的频率和波长。
wave speed = frequency × wavelength
In symbols: v = f × λ, where v is wave speed (m/s), f is frequency in hertz (Hz) and λ (lambda) is wavelength in metres (m).
用符号表示：v = f × λ，其中 v 为波速（m/s），f 为频率，单位赫兹（Hz），λ（lambda）为波长，单位米（m）。
Frequency is the number of complete waves passing a point per second. The amplitude is the maximum displacement from the rest position.
频率是每秒通过某点的完整波的个数。振幅是离开平衡位置的最大位移。
11. Conservation of Energy | 能量守恒定律
The principle of conservation of energy states that energy cannot be created or destroyed. It can only be transferred from one form to another or moved from one place to another.
能量守恒定律指出，能量既不会凭空产生，也不会凭空消失。它只能从一种形式转化为另一种形式，或从一个物体转移到另一个物体。
In any process, the total energy before the change is equal to the total energy after, even if some of it becomes less useful forms like heat.
在任何过程中，变化前的总能量等于变化后的总能量，即使其中一部分转化为不太有用的形式，比如热。
This law helps you track energy in systems such as a swinging pendulum (GPE ↔ KE) or a roller coaster.
这一定律能帮助你追踪系统中的能量转化，例如摇摆的钟摆（重力势能与动能之间的相互转化）或过山车。
Published by TutorHao | Physics Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导