📚 Year 9 AQA Physics: Formula & Theorem Quick Reference | Year 9 AQA 物理：公式定理速查手册
This quick reference guide brings together the essential formulas, key definitions and fundamental theorems you need for Year 9 AQA Physics. Understanding these relationships, their symbols and units will strengthen your problem-solving skills and prepare you for end-of-topic tests and end-of-year exams.
这本速查手册汇集了 Year 9 AQA 物理课程中必须掌握的公式、关键定义和基本定理。理解这些关系、符号和单位，能有效提升解题能力，为章节测验和年终考试做好充分准备。
1. Speed and Velocity | 速度与速率
Speed tells you how fast an object moves. It is a scalar quantity, meaning it only has magnitude. The formula is v = d / t, where v is speed in metres per second (m/s), d is distance in metres (m) and t is time in seconds (s).
速度描述物体运动的快慢。它是标量，只有大小。公式为 v = d / t，其中 v 是速度（米每秒，m/s），d 是距离（米，m），t 是时间（秒，s）。
Velocity is speed in a stated direction. It is a vector quantity, so both magnitude and direction matter. The magnitude of velocity is calculated using the same speed formula, but the answer must include the direction of travel.
速率是带有方向的速度，是矢量，既要有大小也要有方向。速率的大小用相同的速度公式计算，但答案必须包含运动方向。
2. Acceleration | 加速度
Acceleration is the rate at which an object's velocity changes. If velocity increases, acceleration is positive; if velocity decreases (deceleration), acceleration is negative. The formula is a = (v − u) / t, where a is acceleration in metres per second squared (m/s²), v is final velocity (m/s), u is initial velocity (m/s) and t is time (s).
加速度表示物体速度变化的快慢。速度增大时加速度为正，速度减小（减速）时加速度为负。公式为 a = (v − u) / t，其中 a 是加速度（米每二次方秒，m/s²），v 是末速度（m/s），u 是初速度（m/s），t 是时间（s）。
orm if you have displacement. In Year 9, most calculations focus on uniform (constant) acceleration.
可对方程变形求解未知量，如 v = u + a t。若有位移也可使用运动学形式。在九年级，多数计算关注匀（恒定）加速度。
3. Newton’s Laws of Motion | 牛顿运动定律
Newton’s First Law: A resultant force is needed to change the motion of an object. Without a resultant force, an object will remain stationary or continue moving at constant velocity.
牛顿第一定律：物体运动状态的改变需要合力。若合力为零，物体将保持静止或匀速直线运动。
Newton’s Second Law gives the relationship between force, mass and acceleration: F = m a. Force F is measured in newtons (N), mass m in kilograms (kg) and acceleration a in m/s². One newton is the force needed to accelerate 1 kg by 1 m/s².
牛顿第二定律给出了力、质量和加速度的关系：F = m a。力 F 的单位是牛顿（N），质量 m 的单位是千克（kg），加速度 a 的单位是 m/s²。1 牛顿是使 1 kg 物体产生 1 m/s² 加速度所需的力。
Newton’s Third Law: Whenever two objects interact, the forces they exert on each other are equal in magnitude and opposite in direction. These action–reaction pairs act on different objects.
牛顿第三定律：两个物体相互作用时，彼此施加的力大小相等、方向相反。这对作用力与反作用力作用在不同物体上。
4. Mass, Weight and Gravity | 质量、重量与重力
Mass is the amount of matter in an object, measured in kilograms (kg). It does not change with location. Weight is the force of gravity on that mass and depends on gravitational field strength g. The formula is W = m g tional field strength. On Earth, g ≈ 9.8 N/kg (often rounded to 10 N/kg for Year 9 tasks).
质量是物体所含物质的多少，以千克（kg）为单位，不随位置改变。重量是重力对质量的作用力，与引力场强 g 有关。公式为 W = m g，重量 W 的单位为牛顿（N），质量 m 为千克，g 为引力场强。在地球表面 g ≈ 9.8 N/kg（九年级练习常取 10 N/kg）。
Always distinguish between mass and weight: mass is a scalar measured on a balance, weight is a vector measured with a force meter.
务必区分质量与重量：质量是标量，用天平测量；重量是矢量，用测力计测量。
5. Pressure | 压强
Pressure is the force applied per unit area. It tells you how concentrated a force is. The formula is p = F / A, where pressure p is in pascals (Pa), force F is in newtons (N) and area A is in square metres (m²).
压强是单位面积上所受的力，表示力的集中程度。公式为 p = F / A，压强 p 的单位为帕斯卡（Pa），力 F 的单位为牛（N），面积 A 的单位为平方米（m²）。
A larger area over which a force acts results in smaller pressure. For example, a sharp knife has a small edge area, producing a high pressure.
受力面积越大，压强越小。例如，锋利小刀的接触面积很小，能产生较大压强。
6. Work Done and Energy | 做功与能量
Work is done when a force moves an object in the direction of the force. Energy is transferred mechanically. The formula for work done is W = F d, where work W is in joules (J), force F in newtons (N) and distance d (moved in the direction of the force) in metres (m).
力使物体沿力的方向移动时做了功，能量以机械形式转移。做功的公式为 W = F d，功 W 的单位是焦耳（J），力 F 的单位是牛（N），距离 d（沿力的方向移动的距离）的单位是米（m）。
Gravitational potential energy (GPE) stored when lifting an object: GPE = m g h, where h is the height gained in metres (m). Kinetic energy (KE) of a moving object: KE = ½ m v², where v is speed in m/s. Both GPE and KE are measured in joules.
物体被举高时存储的重力势能：GPE = m g h，其中 h 是上升的高度（m）。运动物体的动能：KE = ½ m v²，其中 v 是速度（m/s）。重力势能和动能的单位都是焦耳。
Energy is conserved: in closed systems, total energy stays constant, changing from one form to another.
能量守恒：在封闭系统中，总能量保持不变，仅在不同形式间转化。
7. Power | 功率
Power is the rate of energy transfer or the rate of doing work. The formula is P = E / t or P = W / t, where power P is in watts (W), energy transferred E or work done W is in joules (J) and time t is in seconds (s).
功率是能量转移或做功的速率。公式为 P = E / t 或 P = W / t，功率 P 的单位是瓦特（W），传递的能量 E 或做功 W 的单位是焦耳（J），时间 t 的单位是秒（s）。
One watt equals one joule per second. More powerful devices transfer more energy each second.
1 瓦特等于每秒传递 1 焦耳能量。功率越大的设备每秒转移的能量越多。
8. Density | 密度
Density measures how much mass is packed into a given volume. It is a material property. The formula is ρ = m / V, where density ρ (rho) is in kilograms per metre cubed (kg/m³), mass m in kilograms (kg) and volume V in cubic metres (m³).
密度反映了单位体积内所含质量的多少，是材料的特性。公式为 ρ = m / V，密度 ρ 的单位是千克每立方米（kg/m³），质量 m 的单位是千克（kg），体积 V 的单位是立方米（m³）。
u may also use grams per centimetre cubed (g/cm³) for small samples. 1 g/cm³ = 1000 kg/m³.
小样品也可用克每立方厘米（g/cm³），1 g/cm³ = 1000 kg/m³。
9. Electric Current and Charge | 电流与电荷
Electric current is the rate of flow of electric charge. The formula is I = Q / t, where current I is in amperes (A), charge Q is in coulombs (C) and time t is in seconds (s).
电流是电荷流动的速率。公式为 I = Q / t，电流 I 的单位是安培（A），电荷 Q 的单位是库仑（C），时间 t 的单位是秒（s）。
One ampere means one coulomb of charge passes a point in one second. In metals, the charge is carried by electrons.
1 安培表示每秒有 1 库仑电荷通过某一点。在金属中，电荷由电子携带。
10. Ohm’s Law and Resistance | 欧姆定律与电阻
Ohm’s Law states that the current through a resistor at constant temperature is proportional to the potential difference (voltage) across it. The formula is V = I R, where V is voltage in volts (V), I is current in amperes (A) and R is resistance in ohms (Ω).
欧姆定律指出，在温度不变时，通过电阻的电流与电阻两端的电势差（电压）成正比。公式为 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）。
ge to find resistance: R = V / I. A higher resistance reduces current for a given voltage.
变形可得电阻 R = V / I。在给定电压下，电阻越大，电流越小。
For resistors in series: total resistance Rtotal = R1 + R2 + ... For resistors in parallel: the reciprocal formula 1 / Rtotal = 1 / R1 + 1 / R2 + ...
串联电阻：总电阻 Rtotal = R1 + R2 + ... 并联电阻：用倒数公式 1 / Rtotal = 1 / R1 + 1 / R2 + ...
11. Wave Speed | 波速
All waves obey the wave speed equation: v = f λ, where v is wave speed in metres per second (m/s), f is frequency in hertz (Hz) and λ (lambda) is wavelength in metres (m).
所有波都遵循波速公式：v = f λ，波速 v 的单位是米每秒（m/s），频率 f 的单位是赫兹（Hz），波长 λ 的单位是米（m）。
Frequency is the number of complete waves passing a point per second. Wavelength is the distance between two consecutive identical points on a wave.
频率是每秒通过某点的完整波个数。波长是波上两个连续相同点之间的距离。
12. Efficiency | 效率
Efficiency measures how well energy is converted to a useful form. No device is 100% efficient; some energy is always dissipated, usually as heat. The efficiency formula is Efficiency = (useful output energy / total input energy) × 100%.
效率衡量能量转化为有用形式的程度。没有设备能达到 100% 效率，总有能量耗散（通常以热的形式）。效率公式为 效率 = (有用输出能量 / 总输入能量) × 100%。
You can also use power: efficiency = (useful power output / total power input) × 100%. Efficiency has no units and should be expressed as a percentage or a decimal.
也可以用功率计算：效率 = (有用输出功率 / 总输入功率) × 100%。效率无单位，通常以百分比或小数表示。
Energy is dissipated in thermal stores, causing heating of the surroundings.
能量被耗散到热储存中，导致周围环境升温。
Published by TutorHao | Physics Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图