📚 IB Physics Core Revision: Measurements, Mechanics, Waves and Quantum | IB 物理核心复习：测量、力学、波与量子
Welcome to this IB Physics revision guide. It pulls together the core topics that frequently appear in Paper 1, Paper 2 and the Internal Assessment. Use it alongside Helen Reynolds' Activate Physics Student Book to check definitions, practise calculations and sharpen your exam technique.
欢迎使用本 IB 物理复习指南。本指南汇总了试卷一、试卷二和内部评估中频繁出现的核心主题。可结合 Helen Reynolds 主编的 Activate Physics Student Book 使用，以检查定义、练习计算并提升应试技巧。
1. Measurements and Uncertainties | 测量与不确定度
IB Physics rewards precise measurement, consistent units and honest reporting of uncertainty. The SI base units - kilogram, metre, second, ampere, kelvin, mole and candela - allow every derived unit to be expressed clearly. When you take a reading, distinguish between random uncertainty and systematic error: random uncertainty can be reduced by repeating measurements, while systematic error requires recalibration.
IB 物理注重精确测量、单位一致和如实报告不确定度。SI 基本单位——千克、米、秒、安培、开尔文、摩尔和坎德拉——使每个导出单位都能清晰地表示。读数时要区分随机不确定度和系统误差：随机不确定度可通过重复测量减小，系统误差则需重新校准。
Absolute uncertainty is the raw spread in a measurement, fractional uncertainty is absolute uncertainty divided by the measured value, and percentage uncertainty multiplies that by 100. When quantities are added or subtracted, add absolute uncertainties; when multiplied or divided, add percentage uncertainties.
绝对不确定度是测量的原始散布，分数不确定度是绝对不确定度除以测量值，百分数不确定度再乘以 100。量相加或相减时，将绝对不确定度相加；量相乘或相除时，将百分比不确定度相加。
Δx = |x₂ - x₁|; uncertainty = ± ½ (max - min)
2. Kinematics and Projectile Motion | 运动学与抛体运动
Kinematics describes motion without asking about its causes. Displacement, velocity and acceleration are vector quantities, so direction matters. The four suvat equations connect initial velocity u, final velocity v, acceleration a, displacement s and time t for constant acceleration.
运动学描述运动而不探究其成因。位移、速度和加速度是矢量，因此方向非常重要。四个 suvat 方程把初速度 u、末速度 v、加速度 a、位移 s 和时间 t 联系起来，适用于匀变速运动。
al velocity into components, then apply suvat equations separately. At the highest point, vertical velocity is zero, but horizontal velocity remains unchanged.
在抛体运动中，水平与竖直分量相互独立：若忽略空气阻力，水平速度恒定，竖直方向则具有向下的加速度 g = 9.81 m s⁻²。先将初速度分解为两个分量，再分别应用 suvat 方程。在最高点，竖直速度为零，但水平速度保持不变。
v = u + at; s = ut + ½at²; v² = u² + 2as; s = ½(u+v)t
3. Forces, Newton's Laws and Momentum | 力、牛顿定律与动量
Newton' is proportional to resultant force and inversely proportional to mass. The third law reminds us that forces come in equal and opposite pairs acting on different bodies.
牛顿三定律支配着力与运动。第一定律指出，除非受到合力作用，物体将保持静止或匀速直线运动。第二定律 F = ma 表明，加速度与合力成正比，与质量成反比。第三定律提醒我们，力成对出现，大小相等、方向相反，但作用在不同物体上。
lated systems. In collisions, impulse FΔt equals change in momentum Δp, which explains why crumple zones and airbags reduce injury by increasing collision time.
动量 p = mv 在所有孤立系统中守恒。碰撞中，冲量 FΔt 等于动量的变化 Δp，这说明为什么溃缩区和安全气囊通过延长碰撞时间减少伤害。
F = ma; p = mv; FΔt = Δp; m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂
4. Work, Energy and Power | 功、能量与功率
many mechanics problems to be solved by conservation of energy rather than by resolving forces.
当力使其作用点沿力的方向移动时，力就对物体做功。如果力与位移成角度 θ，只有平行分量做功：W = Fs cosθ。动能 Eₖ = ½mv² 和重力势能 Eₚ = mgh 使许多力学问题可以通过能量守恒求解，而不必分解力。
gy transfer. Efficiency compares useful energy or power output with total input; no real process reaches 100% because of friction and heat losses.
功率 P = W/t 衡量能量转移的快慢。效率将有用能量或功率输出与总输入进行比较；由于摩擦和热损失，真实过程无法达到 100%。
W = Fs cosθ; Eₖ = ½mv²; Eₚ = mgh; P = W/t
5. Thermal Physics and Gas Laws | 热学与气体定律
ibes energy absorbed or released during a phase change without temperature change: Q = mL.
热学将日常温度变化与微观粒子运动联系起来。比热容 c 表示 1 kg 物质升高 1 K 所需的能量：Q = mcΔT。比潜热 L 描述相变过程中无温度变化时吸收或释放的能量：Q = mL。
K⁻¹. At constant temperature, pressure and volume are inversely proportional; at constant volume, pressure rises linearly with absolute temperature. The average kinetic energy of a gas particle is proportional to absolute temperature.
对于理想气体，压强、体积和温度遵循 PV = nRT，其中 n 是摩尔数，R = 8.31 J mol⁻¹ K⁻¹。温度不变时，压强与体积成反比；体积不变时，压强随绝对温度线性升高。气体粒子的平均动能与绝对温度成正比。
Q = mcΔT; Q = mL; PV = nRT; pV/T = constant
6. Oscillations and Waves | 振动与波
uency f are related by T = 1/f. Travelling waves carry energy without transporting matter.
当加速度与离开平衡位置的位移成正比且指向平衡位置时，物体做简谐运动：a = -ω²x。周期 T 与频率 f 的关系为 T = 1/f。行波传播能量而不传输物质。
The wave equation v = fλ connects wave speed, frequency and wavelength. When
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